ALSA: pcm: simplify top-up mode init in snd_pcm_playback_silence()

[platform/kernel/linux-rpi.git] / sound / core / pcm_lib.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Digital Audio (PCM) abstract layer
 *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
 *                   Abramo Bagnara <abramo@alsa-project.org>
 */

#include <linux/slab.h>
#include <linux/sched/signal.h>
#include <linux/time.h>
#include <linux/math64.h>
#include <linux/export.h>
#include <sound/core.h>
#include <sound/control.h>
#include <sound/tlv.h>
#include <sound/info.h>
#include <sound/pcm.h>
#include <sound/pcm_params.h>
#include <sound/timer.h>

#include "pcm_local.h"

#ifdef CONFIG_SND_PCM_XRUN_DEBUG
#define CREATE_TRACE_POINTS
#include "pcm_trace.h"
#else
#define trace_hwptr(substream, pos, in_interrupt)
#define trace_xrun(substream)
#define trace_hw_ptr_error(substream, reason)
#define trace_applptr(substream, prev, curr)
#endif

static int fill_silence_frames(struct snd_pcm_substream *substream,
                               snd_pcm_uframes_t off, snd_pcm_uframes_t frames);


static inline void update_silence_vars(struct snd_pcm_runtime *runtime,
                                       snd_pcm_uframes_t ptr,
                                       snd_pcm_uframes_t new_ptr)
{
        snd_pcm_sframes_t delta;

        delta = new_ptr - ptr;
        if (delta == 0)
                return;
        if (delta < 0)
                delta += runtime->boundary;
        if ((snd_pcm_uframes_t)delta < runtime->silence_filled)
                runtime->silence_filled -= delta;
        else
                runtime->silence_filled = 0;
        runtime->silence_start = new_ptr;
}

/*
 * fill ring buffer with silence
 * runtime->silence_start: starting pointer to silence area
 * runtime->silence_filled: size filled with silence
 * runtime->silence_threshold: threshold from application
 * runtime->silence_size: maximal size from application
 *
 * when runtime->silence_size >= runtime->boundary - fill processed area with silence immediately
 */
void snd_pcm_playback_silence(struct snd_pcm_substream *substream, snd_pcm_uframes_t new_hw_ptr)
{
        struct snd_pcm_runtime *runtime = substream->runtime;
        snd_pcm_uframes_t frames, ofs, transfer;
        int err;

        if (runtime->silence_size < runtime->boundary) {
                snd_pcm_sframes_t noise_dist;
                snd_pcm_uframes_t appl_ptr = READ_ONCE(runtime->control->appl_ptr);
                update_silence_vars(runtime, runtime->silence_start, appl_ptr);
                /* initialization outside pointer updates */
                if (new_hw_ptr == ULONG_MAX)
                        new_hw_ptr = runtime->status->hw_ptr;
                /* get hw_avail with the boundary crossing */
                noise_dist = appl_ptr - new_hw_ptr;
                if (noise_dist < 0)
                        noise_dist += runtime->boundary;
                /* total noise distance */
                noise_dist += runtime->silence_filled;
                if (noise_dist >= (snd_pcm_sframes_t) runtime->silence_threshold)
                        return;
                frames = runtime->silence_threshold - noise_dist;
                if (frames > runtime->silence_size)
                        frames = runtime->silence_size;
        } else {
                /*
                 * This filling mode aims at free-running mode (used for example by dmix),
                 * which doesn't update the application pointer.
                 */
                snd_pcm_uframes_t hw_ptr = runtime->status->hw_ptr;
                if (new_hw_ptr == ULONG_MAX) {
                        /*
                         * Initialization, fill the whole unused buffer with silence.
                         *
                         * Usually, this is entered while stopped, before data is queued,
                         * so both pointers are expected to be zero.
                         */
                        snd_pcm_sframes_t avail = runtime->control->appl_ptr - hw_ptr;
                        if (avail < 0)
                                avail += runtime->boundary;
                        /*
                         * In free-running mode, appl_ptr will be zero even while running,
                         * so we end up with a huge number. There is no useful way to
                         * handle this, so we just clear the whole buffer.
                         */
                        runtime->silence_filled = avail > runtime->buffer_size ? 0 : avail;
                        runtime->silence_start = hw_ptr;
                } else {
                        /* Silence the just played area immediately */
                        update_silence_vars(runtime, hw_ptr, new_hw_ptr);
                }
                /*
                 * In this mode, silence_filled actually includes the valid
                 * sample data from the user.
                 */
                frames = runtime->buffer_size - runtime->silence_filled;
        }
        if (snd_BUG_ON(frames > runtime->buffer_size))
                return;
        if (frames == 0)
                return;
        ofs = (runtime->silence_start + runtime->silence_filled) % runtime->buffer_size;
        while (frames > 0) {
                transfer = ofs + frames > runtime->buffer_size ? runtime->buffer_size - ofs : frames;
                err = fill_silence_frames(substream, ofs, transfer);
                snd_BUG_ON(err < 0);
                runtime->silence_filled += transfer;
                frames -= transfer;
                ofs = 0;
        }
        snd_pcm_dma_buffer_sync(substream, SNDRV_DMA_SYNC_DEVICE);
}

#ifdef CONFIG_SND_DEBUG
void snd_pcm_debug_name(struct snd_pcm_substream *substream,
                           char *name, size_t len)
{
        snprintf(name, len, "pcmC%dD%d%c:%d",
                 substream->pcm->card->number,
                 substream->pcm->device,
                 substream->stream ? 'c' : 'p',
                 substream->number);
}
EXPORT_SYMBOL(snd_pcm_debug_name);
#endif

#define XRUN_DEBUG_BASIC        (1<<0)
#define XRUN_DEBUG_STACK        (1<<1)  /* dump also stack */
#define XRUN_DEBUG_JIFFIESCHECK (1<<2)  /* do jiffies check */

#ifdef CONFIG_SND_PCM_XRUN_DEBUG

#define xrun_debug(substream, mask) \
                        ((substream)->pstr->xrun_debug & (mask))
#else
#define xrun_debug(substream, mask)     0
#endif

#define dump_stack_on_xrun(substream) do {                      \
                if (xrun_debug(substream, XRUN_DEBUG_STACK))    \
                        dump_stack();                           \
        } while (0)

/* call with stream lock held */
void __snd_pcm_xrun(struct snd_pcm_substream *substream)
{
        struct snd_pcm_runtime *runtime = substream->runtime;

        trace_xrun(substream);
        if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE) {
                struct timespec64 tstamp;

                snd_pcm_gettime(runtime, &tstamp);
                runtime->status->tstamp.tv_sec = tstamp.tv_sec;
                runtime->status->tstamp.tv_nsec = tstamp.tv_nsec;
        }
        snd_pcm_stop(substream, SNDRV_PCM_STATE_XRUN);
        if (xrun_debug(substream, XRUN_DEBUG_BASIC)) {
                char name[16];
                snd_pcm_debug_name(substream, name, sizeof(name));
                pcm_warn(substream->pcm, "XRUN: %s\n", name);
                dump_stack_on_xrun(substream);
        }
}

#ifdef CONFIG_SND_PCM_XRUN_DEBUG
#define hw_ptr_error(substream, in_interrupt, reason, fmt, args...)     \
        do {                                                            \
                trace_hw_ptr_error(substream, reason);  \
                if (xrun_debug(substream, XRUN_DEBUG_BASIC)) {          \
                        pr_err_ratelimited("ALSA: PCM: [%c] " reason ": " fmt, \
                                           (in_interrupt) ? 'Q' : 'P', ##args); \
                        dump_stack_on_xrun(substream);                  \
                }                                                       \
        } while (0)

#else /* ! CONFIG_SND_PCM_XRUN_DEBUG */

#define hw_ptr_error(substream, fmt, args...) do { } while (0)

#endif

int snd_pcm_update_state(struct snd_pcm_substream *substream,
                         struct snd_pcm_runtime *runtime)
{
        snd_pcm_uframes_t avail;

        avail = snd_pcm_avail(substream);
        if (avail > runtime->avail_max)
                runtime->avail_max = avail;
        if (runtime->state == SNDRV_PCM_STATE_DRAINING) {
                if (avail >= runtime->buffer_size) {
                        snd_pcm_drain_done(substream);
                        return -EPIPE;
                }
        } else {
                if (avail >= runtime->stop_threshold) {
                        __snd_pcm_xrun(substream);
                        return -EPIPE;
                }
        }
        if (runtime->twake) {
                if (avail >= runtime->twake)
                        wake_up(&runtime->tsleep);
        } else if (avail >= runtime->control->avail_min)
                wake_up(&runtime->sleep);
        return 0;
}

static void update_audio_tstamp(struct snd_pcm_substream *substream,
                                struct timespec64 *curr_tstamp,
                                struct timespec64 *audio_tstamp)
{
        struct snd_pcm_runtime *runtime = substream->runtime;
        u64 audio_frames, audio_nsecs;
        struct timespec64 driver_tstamp;

        if (runtime->tstamp_mode != SNDRV_PCM_TSTAMP_ENABLE)
                return;

        if (!(substream->ops->get_time_info) ||
                (runtime->audio_tstamp_report.actual_type ==
                        SNDRV_PCM_AUDIO_TSTAMP_TYPE_DEFAULT)) {

                /*
                 * provide audio timestamp derived from pointer position
                 * add delay only if requested
                 */

                audio_frames = runtime->hw_ptr_wrap + runtime->status->hw_ptr;

                if (runtime->audio_tstamp_config.report_delay) {
                        if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
                                audio_frames -=  runtime->delay;
                        else
                                audio_frames +=  runtime->delay;
                }
                audio_nsecs = div_u64(audio_frames * 1000000000LL,
                                runtime->rate);
                *audio_tstamp = ns_to_timespec64(audio_nsecs);
        }

        if (runtime->status->audio_tstamp.tv_sec != audio_tstamp->tv_sec ||
            runtime->status->audio_tstamp.tv_nsec != audio_tstamp->tv_nsec) {
                runtime->status->audio_tstamp.tv_sec = audio_tstamp->tv_sec;
                runtime->status->audio_tstamp.tv_nsec = audio_tstamp->tv_nsec;
                runtime->status->tstamp.tv_sec = curr_tstamp->tv_sec;
                runtime->status->tstamp.tv_nsec = curr_tstamp->tv_nsec;
        }


        /*
         * re-take a driver timestamp to let apps detect if the reference tstamp
         * read by low-level hardware was provided with a delay
         */
        snd_pcm_gettime(substream->runtime, &driver_tstamp);
        runtime->driver_tstamp = driver_tstamp;
}

static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
                                  unsigned int in_interrupt)
{
        struct snd_pcm_runtime *runtime = substream->runtime;
        snd_pcm_uframes_t pos;
        snd_pcm_uframes_t old_hw_ptr, new_hw_ptr, hw_base;
        snd_pcm_sframes_t hdelta, delta;
        unsigned long jdelta;
        unsigned long curr_jiffies;
        struct timespec64 curr_tstamp;
        struct timespec64 audio_tstamp;
        int crossed_boundary = 0;

        old_hw_ptr = runtime->status->hw_ptr;

        /*
         * group pointer, time and jiffies reads to allow for more
         * accurate correlations/corrections.
         * The values are stored at the end of this routine after
         * corrections for hw_ptr position
         */
        pos = substream->ops->pointer(substream);
        curr_jiffies = jiffies;
        if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE) {
                if ((substream->ops->get_time_info) &&
                        (runtime->audio_tstamp_config.type_requested != SNDRV_PCM_AUDIO_TSTAMP_TYPE_DEFAULT)) {
                        substream->ops->get_time_info(substream, &curr_tstamp,
                                                &audio_tstamp,
                                                &runtime->audio_tstamp_config,
                                                &runtime->audio_tstamp_report);

                        /* re-test in case tstamp type is not supported in hardware and was demoted to DEFAULT */
                        if (runtime->audio_tstamp_report.actual_type == SNDRV_PCM_AUDIO_TSTAMP_TYPE_DEFAULT)
                                snd_pcm_gettime(runtime, &curr_tstamp);
                } else
                        snd_pcm_gettime(runtime, &curr_tstamp);
        }

        if (pos == SNDRV_PCM_POS_XRUN) {
                __snd_pcm_xrun(substream);
                return -EPIPE;
        }
        if (pos >= runtime->buffer_size) {
                if (printk_ratelimit()) {
                        char name[16];
                        snd_pcm_debug_name(substream, name, sizeof(name));
                        pcm_err(substream->pcm,
                                "invalid position: %s, pos = %ld, buffer size = %ld, period size = %ld\n",
                                name, pos, runtime->buffer_size,
                                runtime->period_size);
                }
                pos = 0;
        }
        pos -= pos % runtime->min_align;
        trace_hwptr(substream, pos, in_interrupt);
        hw_base = runtime->hw_ptr_base;
        new_hw_ptr = hw_base + pos;
        if (in_interrupt) {
                /* we know that one period was processed */
                /* delta = "expected next hw_ptr" for in_interrupt != 0 */
                delta = runtime->hw_ptr_interrupt + runtime->period_size;
                if (delta > new_hw_ptr) {
                        /* check for double acknowledged interrupts */
                        hdelta = curr_jiffies - runtime->hw_ptr_jiffies;
                        if (hdelta > runtime->hw_ptr_buffer_jiffies/2 + 1) {
                                hw_base += runtime->buffer_size;
                                if (hw_base >= runtime->boundary) {
                                        hw_base = 0;
                                        crossed_boundary++;
                                }
                                new_hw_ptr = hw_base + pos;
                                goto __delta;
                        }
                }
        }
        /* new_hw_ptr might be lower than old_hw_ptr in case when */
        /* pointer crosses the end of the ring buffer */
        if (new_hw_ptr < old_hw_ptr) {
                hw_base += runtime->buffer_size;
                if (hw_base >= runtime->boundary) {
                        hw_base = 0;
                        crossed_boundary++;
                }
                new_hw_ptr = hw_base + pos;
        }
      __delta:
        delta = new_hw_ptr - old_hw_ptr;
        if (delta < 0)
                delta += runtime->boundary;

        if (runtime->no_period_wakeup) {
                snd_pcm_sframes_t xrun_threshold;
                /*
                 * Without regular period interrupts, we have to check
                 * the elapsed time to detect xruns.
                 */
                jdelta = curr_jiffies - runtime->hw_ptr_jiffies;
                if (jdelta < runtime->hw_ptr_buffer_jiffies / 2)
                        goto no_delta_check;
                hdelta = jdelta - delta * HZ / runtime->rate;
                xrun_threshold = runtime->hw_ptr_buffer_jiffies / 2 + 1;
                while (hdelta > xrun_threshold) {
                        delta += runtime->buffer_size;
                        hw_base += runtime->buffer_size;
                        if (hw_base >= runtime->boundary) {
                                hw_base = 0;
                                crossed_boundary++;
                        }
                        new_hw_ptr = hw_base + pos;
                        hdelta -= runtime->hw_ptr_buffer_jiffies;
                }
                goto no_delta_check;
        }

        /* something must be really wrong */
        if (delta >= runtime->buffer_size + runtime->period_size) {
                hw_ptr_error(substream, in_interrupt, "Unexpected hw_ptr",
                             "(stream=%i, pos=%ld, new_hw_ptr=%ld, old_hw_ptr=%ld)\n",
                             substream->stream, (long)pos,
                             (long)new_hw_ptr, (long)old_hw_ptr);
                return 0;
        }

        /* Do jiffies check only in xrun_debug mode */
        if (!xrun_debug(substream, XRUN_DEBUG_JIFFIESCHECK))
                goto no_jiffies_check;

        /* Skip the jiffies check for hardwares with BATCH flag.
         * Such hardware usually just increases the position at each IRQ,
         * thus it can't give any strange position.
         */
        if (runtime->hw.info & SNDRV_PCM_INFO_BATCH)
                goto no_jiffies_check;
        hdelta = delta;
        if (hdelta < runtime->delay)
                goto no_jiffies_check;
        hdelta -= runtime->delay;
        jdelta = curr_jiffies - runtime->hw_ptr_jiffies;
        if (((hdelta * HZ) / runtime->rate) > jdelta + HZ/100) {
                delta = jdelta /
                        (((runtime->period_size * HZ) / runtime->rate)
                                                                + HZ/100);
                /* move new_hw_ptr according jiffies not pos variable */
                new_hw_ptr = old_hw_ptr;
                hw_base = delta;
                /* use loop to avoid checks for delta overflows */
                /* the delta value is small or zero in most cases */
                while (delta > 0) {
                        new_hw_ptr += runtime->period_size;
                        if (new_hw_ptr >= runtime->boundary) {
                                new_hw_ptr -= runtime->boundary;
                                crossed_boundary--;
                        }
                        delta--;
                }
                /* align hw_base to buffer_size */
                hw_ptr_error(substream, in_interrupt, "hw_ptr skipping",
                             "(pos=%ld, delta=%ld, period=%ld, jdelta=%lu/%lu/%lu, hw_ptr=%ld/%ld)\n",
                             (long)pos, (long)hdelta,
                             (long)runtime->period_size, jdelta,
                             ((hdelta * HZ) / runtime->rate), hw_base,
                             (unsigned long)old_hw_ptr,
                             (unsigned long)new_hw_ptr);
                /* reset values to proper state */
                delta = 0;
                hw_base = new_hw_ptr - (new_hw_ptr % runtime->buffer_size);
        }
 no_jiffies_check:
        if (delta > runtime->period_size + runtime->period_size / 2) {
                hw_ptr_error(substream, in_interrupt,
                             "Lost interrupts?",
                             "(stream=%i, delta=%ld, new_hw_ptr=%ld, old_hw_ptr=%ld)\n",
                             substream->stream, (long)delta,
                             (long)new_hw_ptr,
                             (long)old_hw_ptr);
        }

 no_delta_check:
        if (runtime->status->hw_ptr == new_hw_ptr) {
                runtime->hw_ptr_jiffies = curr_jiffies;
                update_audio_tstamp(substream, &curr_tstamp, &audio_tstamp);
                return 0;
        }

        if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK &&
            runtime->silence_size > 0)
                snd_pcm_playback_silence(substream, new_hw_ptr);

        if (in_interrupt) {
                delta = new_hw_ptr - runtime->hw_ptr_interrupt;
                if (delta < 0)
                        delta += runtime->boundary;
                delta -= (snd_pcm_uframes_t)delta % runtime->period_size;
                runtime->hw_ptr_interrupt += delta;
                if (runtime->hw_ptr_interrupt >= runtime->boundary)
                        runtime->hw_ptr_interrupt -= runtime->boundary;
        }
        runtime->hw_ptr_base = hw_base;
        runtime->status->hw_ptr = new_hw_ptr;
        runtime->hw_ptr_jiffies = curr_jiffies;
        if (crossed_boundary) {
                snd_BUG_ON(crossed_boundary != 1);
                runtime->hw_ptr_wrap += runtime->boundary;
        }

        update_audio_tstamp(substream, &curr_tstamp, &audio_tstamp);

        return snd_pcm_update_state(substream, runtime);
}

/* CAUTION: call it with irq disabled */
int snd_pcm_update_hw_ptr(struct snd_pcm_substream *substream)
{
        return snd_pcm_update_hw_ptr0(substream, 0);
}

/**
 * snd_pcm_set_ops - set the PCM operators
 * @pcm: the pcm instance
 * @direction: stream direction, SNDRV_PCM_STREAM_XXX
 * @ops: the operator table
 *
 * Sets the given PCM operators to the pcm instance.
 */
void snd_pcm_set_ops(struct snd_pcm *pcm, int direction,
                     const struct snd_pcm_ops *ops)
{
        struct snd_pcm_str *stream = &pcm->streams[direction];
        struct snd_pcm_substream *substream;
        
        for (substream = stream->substream; substream != NULL; substream = substream->next)
                substream->ops = ops;
}
EXPORT_SYMBOL(snd_pcm_set_ops);

/**
 * snd_pcm_set_sync - set the PCM sync id
 * @substream: the pcm substream
 *
 * Sets the PCM sync identifier for the card.
 */
void snd_pcm_set_sync(struct snd_pcm_substream *substream)
{
        struct snd_pcm_runtime *runtime = substream->runtime;
        
        runtime->sync.id32[0] = substream->pcm->card->number;
        runtime->sync.id32[1] = -1;
        runtime->sync.id32[2] = -1;
        runtime->sync.id32[3] = -1;
}
EXPORT_SYMBOL(snd_pcm_set_sync);

/*
 *  Standard ioctl routine
 */

static inline unsigned int div32(unsigned int a, unsigned int b, 
                                 unsigned int *r)
{
        if (b == 0) {
                *r = 0;
                return UINT_MAX;
        }
        *r = a % b;
        return a / b;
}

static inline unsigned int div_down(unsigned int a, unsigned int b)
{
        if (b == 0)
                return UINT_MAX;
        return a / b;
}

static inline unsigned int div_up(unsigned int a, unsigned int b)
{
        unsigned int r;
        unsigned int q;
        if (b == 0)
                return UINT_MAX;
        q = div32(a, b, &r);
        if (r)
                ++q;
        return q;
}

static inline unsigned int mul(unsigned int a, unsigned int b)
{
        if (a == 0)
                return 0;
        if (div_down(UINT_MAX, a) < b)
                return UINT_MAX;
        return a * b;
}

static inline unsigned int muldiv32(unsigned int a, unsigned int b,
                                    unsigned int c, unsigned int *r)
{
        u_int64_t n = (u_int64_t) a * b;
        if (c == 0) {
                *r = 0;
                return UINT_MAX;
        }
        n = div_u64_rem(n, c, r);
        if (n >= UINT_MAX) {
                *r = 0;
                return UINT_MAX;
        }
        return n;
}

/**
 * snd_interval_refine - refine the interval value of configurator
 * @i: the interval value to refine
 * @v: the interval value to refer to
 *
 * Refines the interval value with the reference value.
 * The interval is changed to the range satisfying both intervals.
 * The interval status (min, max, integer, etc.) are evaluated.
 *
 * Return: Positive if the value is changed, zero if it's not changed, or a
 * negative error code.
 */
int snd_interval_refine(struct snd_interval *i, const struct snd_interval *v)
{
        int changed = 0;
        if (snd_BUG_ON(snd_interval_empty(i)))
                return -EINVAL;
        if (i->min < v->min) {
                i->min = v->min;
                i->openmin = v->openmin;
                changed = 1;
        } else if (i->min == v->min && !i->openmin && v->openmin) {
                i->openmin = 1;
                changed = 1;
        }
        if (i->max > v->max) {
                i->max = v->max;
                i->openmax = v->openmax;
                changed = 1;
        } else if (i->max == v->max && !i->openmax && v->openmax) {
                i->openmax = 1;
                changed = 1;
        }
        if (!i->integer && v->integer) {
                i->integer = 1;
                changed = 1;
        }
        if (i->integer) {
                if (i->openmin) {
                        i->min++;
                        i->openmin = 0;
                }
                if (i->openmax) {
                        i->max--;
                        i->openmax = 0;
                }
        } else if (!i->openmin && !i->openmax && i->min == i->max)
                i->integer = 1;
        if (snd_interval_checkempty(i)) {
                snd_interval_none(i);
                return -EINVAL;
        }
        return changed;
}
EXPORT_SYMBOL(snd_interval_refine);

static int snd_interval_refine_first(struct snd_interval *i)
{
        const unsigned int last_max = i->max;

        if (snd_BUG_ON(snd_interval_empty(i)))
                return -EINVAL;
        if (snd_interval_single(i))
                return 0;
        i->max = i->min;
        if (i->openmin)
                i->max++;
        /* only exclude max value if also excluded before refine */
        i->openmax = (i->openmax && i->max >= last_max);
        return 1;
}

static int snd_interval_refine_last(struct snd_interval *i)
{
        const unsigned int last_min = i->min;

        if (snd_BUG_ON(snd_interval_empty(i)))
                return -EINVAL;
        if (snd_interval_single(i))
                return 0;
        i->min = i->max;
        if (i->openmax)
                i->min--;
        /* only exclude min value if also excluded before refine */
        i->openmin = (i->openmin && i->min <= last_min);
        return 1;
}

void snd_interval_mul(const struct snd_interval *a, const struct snd_interval *b, struct snd_interval *c)
{
        if (a->empty || b->empty) {
                snd_interval_none(c);
                return;
        }
        c->empty = 0;
        c->min = mul(a->min, b->min);
        c->openmin = (a->openmin || b->openmin);
        c->max = mul(a->max,  b->max);
        c->openmax = (a->openmax || b->openmax);
        c->integer = (a->integer && b->integer);
}

/**
 * snd_interval_div - refine the interval value with division
 * @a: dividend
 * @b: divisor
 * @c: quotient
 *
 * c = a / b
 *
 * Returns non-zero if the value is changed, zero if not changed.
 */
void snd_interval_div(const struct snd_interval *a, const struct snd_interval *b, struct snd_interval *c)
{
        unsigned int r;
        if (a->empty || b->empty) {
                snd_interval_none(c);
                return;
        }
        c->empty = 0;
        c->min = div32(a->min, b->max, &r);
        c->openmin = (r || a->openmin || b->openmax);
        if (b->min > 0) {
                c->max = div32(a->max, b->min, &r);
                if (r) {
                        c->max++;
                        c->openmax = 1;
                } else
                        c->openmax = (a->openmax || b->openmin);
        } else {
                c->max = UINT_MAX;
                c->openmax = 0;
        }
        c->integer = 0;
}

/**
 * snd_interval_muldivk - refine the interval value
 * @a: dividend 1
 * @b: dividend 2
 * @k: divisor (as integer)
 * @c: result
  *
 * c = a * b / k
 *
 * Returns non-zero if the value is changed, zero if not changed.
 */
void snd_interval_muldivk(const struct snd_interval *a, const struct snd_interval *b,
                      unsigned int k, struct snd_interval *c)
{
        unsigned int r;
        if (a->empty || b->empty) {
                snd_interval_none(c);
                return;
        }
        c->empty = 0;
        c->min = muldiv32(a->min, b->min, k, &r);
        c->openmin = (r || a->openmin || b->openmin);
        c->max = muldiv32(a->max, b->max, k, &r);
        if (r) {
                c->max++;
                c->openmax = 1;
        } else
                c->openmax = (a->openmax || b->openmax);
        c->integer = 0;
}

/**
 * snd_interval_mulkdiv - refine the interval value
 * @a: dividend 1
 * @k: dividend 2 (as integer)
 * @b: divisor
 * @c: result
 *
 * c = a * k / b
 *
 * Returns non-zero if the value is changed, zero if not changed.
 */
void snd_interval_mulkdiv(const struct snd_interval *a, unsigned int k,
                      const struct snd_interval *b, struct snd_interval *c)
{
        unsigned int r;
        if (a->empty || b->empty) {
                snd_interval_none(c);
                return;
        }
        c->empty = 0;
        c->min = muldiv32(a->min, k, b->max, &r);
        c->openmin = (r || a->openmin || b->openmax);
        if (b->min > 0) {
                c->max = muldiv32(a->max, k, b->min, &r);
                if (r) {
                        c->max++;
                        c->openmax = 1;
                } else
                        c->openmax = (a->openmax || b->openmin);
        } else {
                c->max = UINT_MAX;
                c->openmax = 0;
        }
        c->integer = 0;
}

/* ---- */


/**
 * snd_interval_ratnum - refine the interval value
 * @i: interval to refine
 * @rats_count: number of ratnum_t 
 * @rats: ratnum_t array
 * @nump: pointer to store the resultant numerator
 * @denp: pointer to store the resultant denominator
 *
 * Return: Positive if the value is changed, zero if it's not changed, or a
 * negative error code.
 */
int snd_interval_ratnum(struct snd_interval *i,
                        unsigned int rats_count, const struct snd_ratnum *rats,
                        unsigned int *nump, unsigned int *denp)
{
        unsigned int best_num, best_den;
        int best_diff;
        unsigned int k;
        struct snd_interval t;
        int err;
        unsigned int result_num, result_den;
        int result_diff;

        best_num = best_den = best_diff = 0;
        for (k = 0; k < rats_count; ++k) {
                unsigned int num = rats[k].num;
                unsigned int den;
                unsigned int q = i->min;
                int diff;
                if (q == 0)
                        q = 1;
                den = div_up(num, q);
                if (den < rats[k].den_min)
                        continue;
                if (den > rats[k].den_max)
                        den = rats[k].den_max;
                else {
                        unsigned int r;
                        r = (den - rats[k].den_min) % rats[k].den_step;
                        if (r != 0)
                                den -= r;
                }
                diff = num - q * den;
                if (diff < 0)
                        diff = -diff;
                if (best_num == 0 ||
                    diff * best_den < best_diff * den) {
                        best_diff = diff;
                        best_den = den;
                        best_num = num;
                }
        }
        if (best_den == 0) {
                i->empty = 1;
                return -EINVAL;
        }
        t.min = div_down(best_num, best_den);
        t.openmin = !!(best_num % best_den);
        
        result_num = best_num;
        result_diff = best_diff;
        result_den = best_den;
        best_num = best_den = best_diff = 0;
        for (k = 0; k < rats_count; ++k) {
                unsigned int num = rats[k].num;
                unsigned int den;
                unsigned int q = i->max;
                int diff;
                if (q == 0) {
                        i->empty = 1;
                        return -EINVAL;
                }
                den = div_down(num, q);
                if (den > rats[k].den_max)
                        continue;
                if (den < rats[k].den_min)
                        den = rats[k].den_min;
                else {
                        unsigned int r;
                        r = (den - rats[k].den_min) % rats[k].den_step;
                        if (r != 0)
                                den += rats[k].den_step - r;
                }
                diff = q * den - num;
                if (diff < 0)
                        diff = -diff;
                if (best_num == 0 ||
                    diff * best_den < best_diff * den) {
                        best_diff = diff;
                        best_den = den;
                        best_num = num;
                }
        }
        if (best_den == 0) {
                i->empty = 1;
                return -EINVAL;
        }
        t.max = div_up(best_num, best_den);
        t.openmax = !!(best_num % best_den);
        t.integer = 0;
        err = snd_interval_refine(i, &t);
        if (err < 0)
                return err;

        if (snd_interval_single(i)) {
                if (best_diff * result_den < result_diff * best_den) {
                        result_num = best_num;
                        result_den = best_den;
                }
                if (nump)
                        *nump = result_num;
                if (denp)
                        *denp = result_den;
        }
        return err;
}
EXPORT_SYMBOL(snd_interval_ratnum);

/**
 * snd_interval_ratden - refine the interval value
 * @i: interval to refine
 * @rats_count: number of struct ratden
 * @rats: struct ratden array
 * @nump: pointer to store the resultant numerator
 * @denp: pointer to store the resultant denominator
 *
 * Return: Positive if the value is changed, zero if it's not changed, or a
 * negative error code.
 */
static int snd_interval_ratden(struct snd_interval *i,
                               unsigned int rats_count,
                               const struct snd_ratden *rats,
                               unsigned int *nump, unsigned int *denp)
{
        unsigned int best_num, best_diff, best_den;
        unsigned int k;
        struct snd_interval t;
        int err;

        best_num = best_den = best_diff = 0;
        for (k = 0; k < rats_count; ++k) {
                unsigned int num;
                unsigned int den = rats[k].den;
                unsigned int q = i->min;
                int diff;
                num = mul(q, den);
                if (num > rats[k].num_max)
                        continue;
                if (num < rats[k].num_min)
                        num = rats[k].num_max;
                else {
                        unsigned int r;
                        r = (num - rats[k].num_min) % rats[k].num_step;
                        if (r != 0)
                                num += rats[k].num_step - r;
                }
                diff = num - q * den;
                if (best_num == 0 ||
                    diff * best_den < best_diff * den) {
                        best_diff = diff;
                        best_den = den;
                        best_num = num;
                }
        }
        if (best_den == 0) {
                i->empty = 1;
                return -EINVAL;
        }
        t.min = div_down(best_num, best_den);
        t.openmin = !!(best_num % best_den);
        
        best_num = best_den = best_diff = 0;
        for (k = 0; k < rats_count; ++k) {
                unsigned int num;
                unsigned int den = rats[k].den;
                unsigned int q = i->max;
                int diff;
                num = mul(q, den);
                if (num < rats[k].num_min)
                        continue;
                if (num > rats[k].num_max)
                        num = rats[k].num_max;
                else {
                        unsigned int r;
                        r = (num - rats[k].num_min) % rats[k].num_step;
                        if (r != 0)
                                num -= r;
                }
                diff = q * den - num;
                if (best_num == 0 ||
                    diff * best_den < best_diff * den) {
                        best_diff = diff;
                        best_den = den;
                        best_num = num;
                }
        }
        if (best_den == 0) {
                i->empty = 1;
                return -EINVAL;
        }
        t.max = div_up(best_num, best_den);
        t.openmax = !!(best_num % best_den);
        t.integer = 0;
        err = snd_interval_refine(i, &t);
        if (err < 0)
                return err;

        if (snd_interval_single(i)) {
                if (nump)
                        *nump = best_num;
                if (denp)
                        *denp = best_den;
        }
        return err;
}

/**
 * snd_interval_list - refine the interval value from the list
 * @i: the interval value to refine
 * @count: the number of elements in the list
 * @list: the value list
 * @mask: the bit-mask to evaluate
 *
 * Refines the interval value from the list.
 * When mask is non-zero, only the elements corresponding to bit 1 are
 * evaluated.
 *
 * Return: Positive if the value is changed, zero if it's not changed, or a
 * negative error code.
 */
int snd_interval_list(struct snd_interval *i, unsigned int count,
                      const unsigned int *list, unsigned int mask)
{
        unsigned int k;
        struct snd_interval list_range;

        if (!count) {
                i->empty = 1;
                return -EINVAL;
        }
        snd_interval_any(&list_range);
        list_range.min = UINT_MAX;
        list_range.max = 0;
        for (k = 0; k < count; k++) {
                if (mask && !(mask & (1 << k)))
                        continue;
                if (!snd_interval_test(i, list[k]))
                        continue;
                list_range.min = min(list_range.min, list[k]);
                list_range.max = max(list_range.max, list[k]);
        }
        return snd_interval_refine(i, &list_range);
}
EXPORT_SYMBOL(snd_interval_list);

/**
 * snd_interval_ranges - refine the interval value from the list of ranges
 * @i: the interval value to refine
 * @count: the number of elements in the list of ranges
 * @ranges: the ranges list
 * @mask: the bit-mask to evaluate
 *
 * Refines the interval value from the list of ranges.
 * When mask is non-zero, only the elements corresponding to bit 1 are
 * evaluated.
 *
 * Return: Positive if the value is changed, zero if it's not changed, or a
 * negative error code.
 */
int snd_interval_ranges(struct snd_interval *i, unsigned int count,
                        const struct snd_interval *ranges, unsigned int mask)
{
        unsigned int k;
        struct snd_interval range_union;
        struct snd_interval range;

        if (!count) {
                snd_interval_none(i);
                return -EINVAL;
        }
        snd_interval_any(&range_union);
        range_union.min = UINT_MAX;
        range_union.max = 0;
        for (k = 0; k < count; k++) {
                if (mask && !(mask & (1 << k)))
                        continue;
                snd_interval_copy(&range, &ranges[k]);
                if (snd_interval_refine(&range, i) < 0)
                        continue;
                if (snd_interval_empty(&range))
                        continue;

                if (range.min < range_union.min) {
                        range_union.min = range.min;
                        range_union.openmin = 1;
                }
                if (range.min == range_union.min && !range.openmin)
                        range_union.openmin = 0;
                if (range.max > range_union.max) {
                        range_union.max = range.max;
                        range_union.openmax = 1;
                }
                if (range.max == range_union.max && !range.openmax)
                        range_union.openmax = 0;
        }
        return snd_interval_refine(i, &range_union);
}
EXPORT_SYMBOL(snd_interval_ranges);

static int snd_interval_step(struct snd_interval *i, unsigned int step)
{
        unsigned int n;
        int changed = 0;
        n = i->min % step;
        if (n != 0 || i->openmin) {
                i->min += step - n;
                i->openmin = 0;
                changed = 1;
        }
        n = i->max % step;
        if (n != 0 || i->openmax) {
                i->max -= n;
                i->openmax = 0;
                changed = 1;
        }
        if (snd_interval_checkempty(i)) {
                i->empty = 1;
                return -EINVAL;
        }
        return changed;
}

/* Info constraints helpers */

/**
 * snd_pcm_hw_rule_add - add the hw-constraint rule
 * @runtime: the pcm runtime instance
 * @cond: condition bits
 * @var: the variable to evaluate
 * @func: the evaluation function
 * @private: the private data pointer passed to function
 * @dep: the dependent variables
 *
 * Return: Zero if successful, or a negative error code on failure.
 */
int snd_pcm_hw_rule_add(struct snd_pcm_runtime *runtime, unsigned int cond,
                        int var,
                        snd_pcm_hw_rule_func_t func, void *private,
                        int dep, ...)
{
        struct snd_pcm_hw_constraints *constrs = &runtime->hw_constraints;
        struct snd_pcm_hw_rule *c;
        unsigned int k;
        va_list args;
        va_start(args, dep);
        if (constrs->rules_num >= constrs->rules_all) {
                struct snd_pcm_hw_rule *new;
                unsigned int new_rules = constrs->rules_all + 16;
                new = krealloc_array(constrs->rules, new_rules,
                                     sizeof(*c), GFP_KERNEL);
                if (!new) {
                        va_end(args);
                        return -ENOMEM;
                }
                constrs->rules = new;
                constrs->rules_all = new_rules;
        }
        c = &constrs->rules[constrs->rules_num];
        c->cond = cond;
        c->func = func;
        c->var = var;
        c->private = private;
        k = 0;
        while (1) {
                if (snd_BUG_ON(k >= ARRAY_SIZE(c->deps))) {
                        va_end(args);
                        return -EINVAL;
                }
                c->deps[k++] = dep;
                if (dep < 0)
                        break;
                dep = va_arg(args, int);
        }
        constrs->rules_num++;
        va_end(args);
        return 0;
}
EXPORT_SYMBOL(snd_pcm_hw_rule_add);

/**
 * snd_pcm_hw_constraint_mask - apply the given bitmap mask constraint
 * @runtime: PCM runtime instance
 * @var: hw_params variable to apply the mask
 * @mask: the bitmap mask
 *
 * Apply the constraint of the given bitmap mask to a 32-bit mask parameter.
 *
 * Return: Zero if successful, or a negative error code on failure.
 */
int snd_pcm_hw_constraint_mask(struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var,
                               u_int32_t mask)
{
        struct snd_pcm_hw_constraints *constrs = &runtime->hw_constraints;
        struct snd_mask *maskp = constrs_mask(constrs, var);
        *maskp->bits &= mask;
        memset(maskp->bits + 1, 0, (SNDRV_MASK_MAX-32) / 8); /* clear rest */
        if (*maskp->bits == 0)
                return -EINVAL;
        return 0;
}

/**
 * snd_pcm_hw_constraint_mask64 - apply the given bitmap mask constraint
 * @runtime: PCM runtime instance
 * @var: hw_params variable to apply the mask
 * @mask: the 64bit bitmap mask
 *
 * Apply the constraint of the given bitmap mask to a 64-bit mask parameter.
 *
 * Return: Zero if successful, or a negative error code on failure.
 */
int snd_pcm_hw_constraint_mask64(struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var,
                                 u_int64_t mask)
{
        struct snd_pcm_hw_constraints *constrs = &runtime->hw_constraints;
        struct snd_mask *maskp = constrs_mask(constrs, var);
        maskp->bits[0] &= (u_int32_t)mask;
        maskp->bits[1] &= (u_int32_t)(mask >> 32);
        memset(maskp->bits + 2, 0, (SNDRV_MASK_MAX-64) / 8); /* clear rest */
        if (! maskp->bits[0] && ! maskp->bits[1])
                return -EINVAL;
        return 0;
}
EXPORT_SYMBOL(snd_pcm_hw_constraint_mask64);

/**
 * snd_pcm_hw_constraint_integer - apply an integer constraint to an interval
 * @runtime: PCM runtime instance
 * @var: hw_params variable to apply the integer constraint
 *
 * Apply the constraint of integer to an interval parameter.
 *
 * Return: Positive if the value is changed, zero if it's not changed, or a
 * negative error code.
 */
int snd_pcm_hw_constraint_integer(struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var)
{
        struct snd_pcm_hw_constraints *constrs = &runtime->hw_constraints;
        return snd_interval_setinteger(constrs_interval(constrs, var));
}
EXPORT_SYMBOL(snd_pcm_hw_constraint_integer);

/**
 * snd_pcm_hw_constraint_minmax - apply a min/max range constraint to an interval
 * @runtime: PCM runtime instance
 * @var: hw_params variable to apply the range
 * @min: the minimal value
 * @max: the maximal value
 * 
 * Apply the min/max range constraint to an interval parameter.
 *
 * Return: Positive if the value is changed, zero if it's not changed, or a
 * negative error code.
 */
int snd_pcm_hw_constraint_minmax(struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var,
                                 unsigned int min, unsigned int max)
{
        struct snd_pcm_hw_constraints *constrs = &runtime->hw_constraints;
        struct snd_interval t;
        t.min = min;
        t.max = max;
        t.openmin = t.openmax = 0;
        t.integer = 0;
        return snd_interval_refine(constrs_interval(constrs, var), &t);
}
EXPORT_SYMBOL(snd_pcm_hw_constraint_minmax);

static int snd_pcm_hw_rule_list(struct snd_pcm_hw_params *params,
                                struct snd_pcm_hw_rule *rule)
{
        struct snd_pcm_hw_constraint_list *list = rule->private;
        return snd_interval_list(hw_param_interval(params, rule->var), list->count, list->list, list->mask);
}               


/**
 * snd_pcm_hw_constraint_list - apply a list of constraints to a parameter
 * @runtime: PCM runtime instance
 * @cond: condition bits
 * @var: hw_params variable to apply the list constraint
 * @l: list
 * 
 * Apply the list of constraints to an interval parameter.
 *
 * Return: Zero if successful, or a negative error code on failure.
 */
int snd_pcm_hw_constraint_list(struct snd_pcm_runtime *runtime,
                               unsigned int cond,
                               snd_pcm_hw_param_t var,
                               const struct snd_pcm_hw_constraint_list *l)
{
        return snd_pcm_hw_rule_add(runtime, cond, var,
                                   snd_pcm_hw_rule_list, (void *)l,
                                   var, -1);
}
EXPORT_SYMBOL(snd_pcm_hw_constraint_list);

static int snd_pcm_hw_rule_ranges(struct snd_pcm_hw_params *params,
                                  struct snd_pcm_hw_rule *rule)
{
        struct snd_pcm_hw_constraint_ranges *r = rule->private;
        return snd_interval_ranges(hw_param_interval(params, rule->var),
                                   r->count, r->ranges, r->mask);
}


/**
 * snd_pcm_hw_constraint_ranges - apply list of range constraints to a parameter
 * @runtime: PCM runtime instance
 * @cond: condition bits
 * @var: hw_params variable to apply the list of range constraints
 * @r: ranges
 *
 * Apply the list of range constraints to an interval parameter.
 *
 * Return: Zero if successful, or a negative error code on failure.
 */
int snd_pcm_hw_constraint_ranges(struct snd_pcm_runtime *runtime,
                                 unsigned int cond,
                                 snd_pcm_hw_param_t var,
                                 const struct snd_pcm_hw_constraint_ranges *r)
{
        return snd_pcm_hw_rule_add(runtime, cond, var,
                                   snd_pcm_hw_rule_ranges, (void *)r,
                                   var, -1);
}
EXPORT_SYMBOL(snd_pcm_hw_constraint_ranges);

static int snd_pcm_hw_rule_ratnums(struct snd_pcm_hw_params *params,
                                   struct snd_pcm_hw_rule *rule)
{
        const struct snd_pcm_hw_constraint_ratnums *r = rule->private;
        unsigned int num = 0, den = 0;
        int err;
        err = snd_interval_ratnum(hw_param_interval(params, rule->var),
                                  r->nrats, r->rats, &num, &den);
        if (err >= 0 && den && rule->var == SNDRV_PCM_HW_PARAM_RATE) {
                params->rate_num = num;
                params->rate_den = den;
        }
        return err;
}

/**
 * snd_pcm_hw_constraint_ratnums - apply ratnums constraint to a parameter
 * @runtime: PCM runtime instance
 * @cond: condition bits
 * @var: hw_params variable to apply the ratnums constraint
 * @r: struct snd_ratnums constriants
 *
 * Return: Zero if successful, or a negative error code on failure.
 */
int snd_pcm_hw_constraint_ratnums(struct snd_pcm_runtime *runtime, 
                                  unsigned int cond,
                                  snd_pcm_hw_param_t var,
                                  const struct snd_pcm_hw_constraint_ratnums *r)
{
        return snd_pcm_hw_rule_add(runtime, cond, var,
                                   snd_pcm_hw_rule_ratnums, (void *)r,
                                   var, -1);
}
EXPORT_SYMBOL(snd_pcm_hw_constraint_ratnums);

static int snd_pcm_hw_rule_ratdens(struct snd_pcm_hw_params *params,
                                   struct snd_pcm_hw_rule *rule)
{
        const struct snd_pcm_hw_constraint_ratdens *r = rule->private;
        unsigned int num = 0, den = 0;
        int err = snd_interval_ratden(hw_param_interval(params, rule->var),
                                  r->nrats, r->rats, &num, &den);
        if (err >= 0 && den && rule->var == SNDRV_PCM_HW_PARAM_RATE) {
                params->rate_num = num;
                params->rate_den = den;
        }
        return err;
}

/**
 * snd_pcm_hw_constraint_ratdens - apply ratdens constraint to a parameter
 * @runtime: PCM runtime instance
 * @cond: condition bits
 * @var: hw_params variable to apply the ratdens constraint
 * @r: struct snd_ratdens constriants
 *
 * Return: Zero if successful, or a negative error code on failure.
 */
int snd_pcm_hw_constraint_ratdens(struct snd_pcm_runtime *runtime, 
                                  unsigned int cond,
                                  snd_pcm_hw_param_t var,
                                  const struct snd_pcm_hw_constraint_ratdens *r)
{
        return snd_pcm_hw_rule_add(runtime, cond, var,
                                   snd_pcm_hw_rule_ratdens, (void *)r,
                                   var, -1);
}
EXPORT_SYMBOL(snd_pcm_hw_constraint_ratdens);

static int snd_pcm_hw_rule_msbits(struct snd_pcm_hw_params *params,
                                  struct snd_pcm_hw_rule *rule)
{
        unsigned int l = (unsigned long) rule->private;
        int width = l & 0xffff;
        unsigned int msbits = l >> 16;
        const struct snd_interval *i =
                hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_SAMPLE_BITS);

        if (!snd_interval_single(i))
                return 0;

        if ((snd_interval_value(i) == width) ||
            (width == 0 && snd_interval_value(i) > msbits))
                params->msbits = min_not_zero(params->msbits, msbits);

        return 0;
}

/**
 * snd_pcm_hw_constraint_msbits - add a hw constraint msbits rule
 * @runtime: PCM runtime instance
 * @cond: condition bits
 * @width: sample bits width
 * @msbits: msbits width
 *
 * This constraint will set the number of most significant bits (msbits) if a
 * sample format with the specified width has been select. If width is set to 0
 * the msbits will be set for any sample format with a width larger than the
 * specified msbits.
 *
 * Return: Zero if successful, or a negative error code on failure.
 */
int snd_pcm_hw_constraint_msbits(struct snd_pcm_runtime *runtime, 
                                 unsigned int cond,
                                 unsigned int width,
                                 unsigned int msbits)
{
        unsigned long l = (msbits << 16) | width;
        return snd_pcm_hw_rule_add(runtime, cond, -1,
                                    snd_pcm_hw_rule_msbits,
                                    (void*) l,
                                    SNDRV_PCM_HW_PARAM_SAMPLE_BITS, -1);
}
EXPORT_SYMBOL(snd_pcm_hw_constraint_msbits);

static int snd_pcm_hw_rule_step(struct snd_pcm_hw_params *params,
                                struct snd_pcm_hw_rule *rule)
{
        unsigned long step = (unsigned long) rule->private;
        return snd_interval_step(hw_param_interval(params, rule->var), step);
}

/**
 * snd_pcm_hw_constraint_step - add a hw constraint step rule
 * @runtime: PCM runtime instance
 * @cond: condition bits
 * @var: hw_params variable to apply the step constraint
 * @step: step size
 *
 * Return: Zero if successful, or a negative error code on failure.
 */
int snd_pcm_hw_constraint_step(struct snd_pcm_runtime *runtime,
                               unsigned int cond,
                               snd_pcm_hw_param_t var,
                               unsigned long step)
{
        return snd_pcm_hw_rule_add(runtime, cond, var, 
                                   snd_pcm_hw_rule_step, (void *) step,
                                   var, -1);
}
EXPORT_SYMBOL(snd_pcm_hw_constraint_step);

static int snd_pcm_hw_rule_pow2(struct snd_pcm_hw_params *params, struct snd_pcm_hw_rule *rule)
{
        static const unsigned int pow2_sizes[] = {
                1<<0, 1<<1, 1<<2, 1<<3, 1<<4, 1<<5, 1<<6, 1<<7,
                1<<8, 1<<9, 1<<10, 1<<11, 1<<12, 1<<13, 1<<14, 1<<15,
                1<<16, 1<<17, 1<<18, 1<<19, 1<<20, 1<<21, 1<<22, 1<<23,
                1<<24, 1<<25, 1<<26, 1<<27, 1<<28, 1<<29, 1<<30
        };
        return snd_interval_list(hw_param_interval(params, rule->var),
                                 ARRAY_SIZE(pow2_sizes), pow2_sizes, 0);
}               

/**
 * snd_pcm_hw_constraint_pow2 - add a hw constraint power-of-2 rule
 * @runtime: PCM runtime instance
 * @cond: condition bits
 * @var: hw_params variable to apply the power-of-2 constraint
 *
 * Return: Zero if successful, or a negative error code on failure.
 */
int snd_pcm_hw_constraint_pow2(struct snd_pcm_runtime *runtime,
                               unsigned int cond,
                               snd_pcm_hw_param_t var)
{
        return snd_pcm_hw_rule_add(runtime, cond, var, 
                                   snd_pcm_hw_rule_pow2, NULL,
                                   var, -1);
}
EXPORT_SYMBOL(snd_pcm_hw_constraint_pow2);

static int snd_pcm_hw_rule_noresample_func(struct snd_pcm_hw_params *params,
                                           struct snd_pcm_hw_rule *rule)
{
        unsigned int base_rate = (unsigned int)(uintptr_t)rule->private;
        struct snd_interval *rate;

        rate = hw_param_interval(params, SNDRV_PCM_HW_PARAM_RATE);
        return snd_interval_list(rate, 1, &base_rate, 0);
}

/**
 * snd_pcm_hw_rule_noresample - add a rule to allow disabling hw resampling
 * @runtime: PCM runtime instance
 * @base_rate: the rate at which the hardware does not resample
 *
 * Return: Zero if successful, or a negative error code on failure.
 */
int snd_pcm_hw_rule_noresample(struct snd_pcm_runtime *runtime,
                               unsigned int base_rate)
{
        return snd_pcm_hw_rule_add(runtime, SNDRV_PCM_HW_PARAMS_NORESAMPLE,
                                   SNDRV_PCM_HW_PARAM_RATE,
                                   snd_pcm_hw_rule_noresample_func,
                                   (void *)(uintptr_t)base_rate,
                                   SNDRV_PCM_HW_PARAM_RATE, -1);
}
EXPORT_SYMBOL(snd_pcm_hw_rule_noresample);

static void _snd_pcm_hw_param_any(struct snd_pcm_hw_params *params,
                                  snd_pcm_hw_param_t var)
{
        if (hw_is_mask(var)) {
                snd_mask_any(hw_param_mask(params, var));
                params->cmask |= 1 << var;
                params->rmask |= 1 << var;
                return;
        }
        if (hw_is_interval(var)) {
                snd_interval_any(hw_param_interval(params, var));
                params->cmask |= 1 << var;
                params->rmask |= 1 << var;
                return;
        }
        snd_BUG();
}

void _snd_pcm_hw_params_any(struct snd_pcm_hw_params *params)
{
        unsigned int k;
        memset(params, 0, sizeof(*params));
        for (k = SNDRV_PCM_HW_PARAM_FIRST_MASK; k <= SNDRV_PCM_HW_PARAM_LAST_MASK; k++)
                _snd_pcm_hw_param_any(params, k);
        for (k = SNDRV_PCM_HW_PARAM_FIRST_INTERVAL; k <= SNDRV_PCM_HW_PARAM_LAST_INTERVAL; k++)
                _snd_pcm_hw_param_any(params, k);
        params->info = ~0U;
}
EXPORT_SYMBOL(_snd_pcm_hw_params_any);

/**
 * snd_pcm_hw_param_value - return @params field @var value
 * @params: the hw_params instance
 * @var: parameter to retrieve
 * @dir: pointer to the direction (-1,0,1) or %NULL
 *
 * Return: The value for field @var if it's fixed in configuration space
 * defined by @params. -%EINVAL otherwise.
 */
int snd_pcm_hw_param_value(const struct snd_pcm_hw_params *params,
                           snd_pcm_hw_param_t var, int *dir)
{
        if (hw_is_mask(var)) {
                const struct snd_mask *mask = hw_param_mask_c(params, var);
                if (!snd_mask_single(mask))
                        return -EINVAL;
                if (dir)
                        *dir = 0;
                return snd_mask_value(mask);
        }
        if (hw_is_interval(var)) {
                const struct snd_interval *i = hw_param_interval_c(params, var);
                if (!snd_interval_single(i))
                        return -EINVAL;
                if (dir)
                        *dir = i->openmin;
                return snd_interval_value(i);
        }
        return -EINVAL;
}
EXPORT_SYMBOL(snd_pcm_hw_param_value);

void _snd_pcm_hw_param_setempty(struct snd_pcm_hw_params *params,
                                snd_pcm_hw_param_t var)
{
        if (hw_is_mask(var)) {
                snd_mask_none(hw_param_mask(params, var));
                params->cmask |= 1 << var;
                params->rmask |= 1 << var;
        } else if (hw_is_interval(var)) {
                snd_interval_none(hw_param_interval(params, var));
                params->cmask |= 1 << var;
                params->rmask |= 1 << var;
        } else {
                snd_BUG();
        }
}
EXPORT_SYMBOL(_snd_pcm_hw_param_setempty);

static int _snd_pcm_hw_param_first(struct snd_pcm_hw_params *params,
                                   snd_pcm_hw_param_t var)
{
        int changed;
        if (hw_is_mask(var))
                changed = snd_mask_refine_first(hw_param_mask(params, var));
        else if (hw_is_interval(var))
                changed = snd_interval_refine_first(hw_param_interval(params, var));
        else
                return -EINVAL;
        if (changed > 0) {
                params->cmask |= 1 << var;
                params->rmask |= 1 << var;
        }
        return changed;
}


/**
 * snd_pcm_hw_param_first - refine config space and return minimum value
 * @pcm: PCM instance
 * @params: the hw_params instance
 * @var: parameter to retrieve
 * @dir: pointer to the direction (-1,0,1) or %NULL
 *
 * Inside configuration space defined by @params remove from @var all
 * values > minimum. Reduce configuration space accordingly.
 *
 * Return: The minimum, or a negative error code on failure.
 */
int snd_pcm_hw_param_first(struct snd_pcm_substream *pcm, 
                           struct snd_pcm_hw_params *params, 
                           snd_pcm_hw_param_t var, int *dir)
{
        int changed = _snd_pcm_hw_param_first(params, var);
        if (changed < 0)
                return changed;
        if (params->rmask) {
                int err = snd_pcm_hw_refine(pcm, params);
                if (err < 0)
                        return err;
        }
        return snd_pcm_hw_param_value(params, var, dir);
}
EXPORT_SYMBOL(snd_pcm_hw_param_first);

static int _snd_pcm_hw_param_last(struct snd_pcm_hw_params *params,
                                  snd_pcm_hw_param_t var)
{
        int changed;
        if (hw_is_mask(var))
                changed = snd_mask_refine_last(hw_param_mask(params, var));
        else if (hw_is_interval(var))
                changed = snd_interval_refine_last(hw_param_interval(params, var));
        else
                return -EINVAL;
        if (changed > 0) {
                params->cmask |= 1 << var;
                params->rmask |= 1 << var;
        }
        return changed;
}


/**
 * snd_pcm_hw_param_last - refine config space and return maximum value
 * @pcm: PCM instance
 * @params: the hw_params instance
 * @var: parameter to retrieve
 * @dir: pointer to the direction (-1,0,1) or %NULL
 *
 * Inside configuration space defined by @params remove from @var all
 * values < maximum. Reduce configuration space accordingly.
 *
 * Return: The maximum, or a negative error code on failure.
 */
int snd_pcm_hw_param_last(struct snd_pcm_substream *pcm, 
                          struct snd_pcm_hw_params *params,
                          snd_pcm_hw_param_t var, int *dir)
{
        int changed = _snd_pcm_hw_param_last(params, var);
        if (changed < 0)
                return changed;
        if (params->rmask) {
                int err = snd_pcm_hw_refine(pcm, params);
                if (err < 0)
                        return err;
        }
        return snd_pcm_hw_param_value(params, var, dir);
}
EXPORT_SYMBOL(snd_pcm_hw_param_last);

static int snd_pcm_lib_ioctl_reset(struct snd_pcm_substream *substream,
                                   void *arg)
{
        struct snd_pcm_runtime *runtime = substream->runtime;
        unsigned long flags;
        snd_pcm_stream_lock_irqsave(substream, flags);
        if (snd_pcm_running(substream) &&
            snd_pcm_update_hw_ptr(substream) >= 0)
                runtime->status->hw_ptr %= runtime->buffer_size;
        else {
                runtime->status->hw_ptr = 0;
                runtime->hw_ptr_wrap = 0;
        }
        snd_pcm_stream_unlock_irqrestore(substream, flags);
        return 0;
}

static int snd_pcm_lib_ioctl_channel_info(struct snd_pcm_substream *substream,
                                          void *arg)
{
        struct snd_pcm_channel_info *info = arg;
        struct snd_pcm_runtime *runtime = substream->runtime;
        int width;
        if (!(runtime->info & SNDRV_PCM_INFO_MMAP)) {
                info->offset = -1;
                return 0;
        }
        width = snd_pcm_format_physical_width(runtime->format);
        if (width < 0)
                return width;
        info->offset = 0;
        switch (runtime->access) {
        case SNDRV_PCM_ACCESS_MMAP_INTERLEAVED:
        case SNDRV_PCM_ACCESS_RW_INTERLEAVED:
                info->first = info->channel * width;
                info->step = runtime->channels * width;
                break;
        case SNDRV_PCM_ACCESS_MMAP_NONINTERLEAVED:
        case SNDRV_PCM_ACCESS_RW_NONINTERLEAVED:
        {
                size_t size = runtime->dma_bytes / runtime->channels;
                info->first = info->channel * size * 8;
                info->step = width;
                break;
        }
        default:
                snd_BUG();
                break;
        }
        return 0;
}

static int snd_pcm_lib_ioctl_fifo_size(struct snd_pcm_substream *substream,
                                       void *arg)
{
        struct snd_pcm_hw_params *params = arg;
        snd_pcm_format_t format;
        int channels;
        ssize_t frame_size;

        params->fifo_size = substream->runtime->hw.fifo_size;
        if (!(substream->runtime->hw.info & SNDRV_PCM_INFO_FIFO_IN_FRAMES)) {
                format = params_format(params);
                channels = params_channels(params);
                frame_size = snd_pcm_format_size(format, channels);
                if (frame_size > 0)
                        params->fifo_size /= frame_size;
        }
        return 0;
}

/**
 * snd_pcm_lib_ioctl - a generic PCM ioctl callback
 * @substream: the pcm substream instance
 * @cmd: ioctl command
 * @arg: ioctl argument
 *
 * Processes the generic ioctl commands for PCM.
 * Can be passed as the ioctl callback for PCM ops.
 *
 * Return: Zero if successful, or a negative error code on failure.
 */
int snd_pcm_lib_ioctl(struct snd_pcm_substream *substream,
                      unsigned int cmd, void *arg)
{
        switch (cmd) {
        case SNDRV_PCM_IOCTL1_RESET:
                return snd_pcm_lib_ioctl_reset(substream, arg);
        case SNDRV_PCM_IOCTL1_CHANNEL_INFO:
                return snd_pcm_lib_ioctl_channel_info(substream, arg);
        case SNDRV_PCM_IOCTL1_FIFO_SIZE:
                return snd_pcm_lib_ioctl_fifo_size(substream, arg);
        }
        return -ENXIO;
}
EXPORT_SYMBOL(snd_pcm_lib_ioctl);

/**
 * snd_pcm_period_elapsed_under_stream_lock() - update the status of runtime for the next period
 *                                              under acquired lock of PCM substream.
 * @substream: the instance of pcm substream.
 *
 * This function is called when the batch of audio data frames as the same size as the period of
 * buffer is already processed in audio data transmission.
 *
 * The call of function updates the status of runtime with the latest position of audio data
 * transmission, checks overrun and underrun over buffer, awaken user processes from waiting for
 * available audio data frames, sampling audio timestamp, and performs stop or drain the PCM
 * substream according to configured threshold.
 *
 * The function is intended to use for the case that PCM driver operates audio data frames under
 * acquired lock of PCM substream; e.g. in callback of any operation of &snd_pcm_ops in process
 * context. In any interrupt context, it's preferrable to use ``snd_pcm_period_elapsed()`` instead
 * since lock of PCM substream should be acquired in advance.
 *
 * Developer should pay enough attention that some callbacks in &snd_pcm_ops are done by the call of
 * function:
 *
 * - .pointer - to retrieve current position of audio data transmission by frame count or XRUN state.
 * - .trigger - with SNDRV_PCM_TRIGGER_STOP at XRUN or DRAINING state.
 * - .get_time_info - to retrieve audio time stamp if needed.
 *
 * Even if more than one periods have elapsed since the last call, you have to call this only once.
 */
void snd_pcm_period_elapsed_under_stream_lock(struct snd_pcm_substream *substream)
{
        struct snd_pcm_runtime *runtime;

        if (PCM_RUNTIME_CHECK(substream))
                return;
        runtime = substream->runtime;

        if (!snd_pcm_running(substream) ||
            snd_pcm_update_hw_ptr0(substream, 1) < 0)
                goto _end;

#ifdef CONFIG_SND_PCM_TIMER
        if (substream->timer_running)
                snd_timer_interrupt(substream->timer, 1);
#endif
 _end:
        snd_kill_fasync(runtime->fasync, SIGIO, POLL_IN);
}
EXPORT_SYMBOL(snd_pcm_period_elapsed_under_stream_lock);

/**
 * snd_pcm_period_elapsed() - update the status of runtime for the next period by acquiring lock of
 *                            PCM substream.
 * @substream: the instance of PCM substream.
 *
 * This function is mostly similar to ``snd_pcm_period_elapsed_under_stream_lock()`` except for
 * acquiring lock of PCM substream voluntarily.
 *
 * It's typically called by any type of IRQ handler when hardware IRQ occurs to notify event that
 * the batch of audio data frames as the same size as the period of buffer is already processed in
 * audio data transmission.
 */
void snd_pcm_period_elapsed(struct snd_pcm_substream *substream)
{
        unsigned long flags;

        if (snd_BUG_ON(!substream))
                return;

        snd_pcm_stream_lock_irqsave(substream, flags);
        snd_pcm_period_elapsed_under_stream_lock(substream);
        snd_pcm_stream_unlock_irqrestore(substream, flags);
}
EXPORT_SYMBOL(snd_pcm_period_elapsed);

/*
 * Wait until avail_min data becomes available
 * Returns a negative error code if any error occurs during operation.
 * The available space is stored on availp.  When err = 0 and avail = 0
 * on the capture stream, it indicates the stream is in DRAINING state.
 */
static int wait_for_avail(struct snd_pcm_substream *substream,
                              snd_pcm_uframes_t *availp)
{
        struct snd_pcm_runtime *runtime = substream->runtime;
        int is_playback = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
        wait_queue_entry_t wait;
        int err = 0;
        snd_pcm_uframes_t avail = 0;
        long wait_time, tout;

        init_waitqueue_entry(&wait, current);
        set_current_state(TASK_INTERRUPTIBLE);
        add_wait_queue(&runtime->tsleep, &wait);

        if (runtime->no_period_wakeup)
                wait_time = MAX_SCHEDULE_TIMEOUT;
        else {
                /* use wait time from substream if available */
                if (substream->wait_time) {
                        wait_time = substream->wait_time;
                } else {
                        wait_time = 100;

                        if (runtime->rate) {
                                long t = runtime->buffer_size * 1100 / runtime->rate;
                                wait_time = max(t, wait_time);
                        }
                }
                wait_time = msecs_to_jiffies(wait_time);
        }

        for (;;) {
                if (signal_pending(current)) {
                        err = -ERESTARTSYS;
                        break;
                }

                /*
                 * We need to check if space became available already
                 * (and thus the wakeup happened already) first to close
                 * the race of space already having become available.
                 * This check must happen after been added to the waitqueue
                 * and having current state be INTERRUPTIBLE.
                 */
                avail = snd_pcm_avail(substream);
                if (avail >= runtime->twake)
                        break;
                snd_pcm_stream_unlock_irq(substream);

                tout = schedule_timeout(wait_time);

                snd_pcm_stream_lock_irq(substream);
                set_current_state(TASK_INTERRUPTIBLE);
                switch (runtime->state) {
                case SNDRV_PCM_STATE_SUSPENDED:
                        err = -ESTRPIPE;
                        goto _endloop;
                case SNDRV_PCM_STATE_XRUN:
                        err = -EPIPE;
                        goto _endloop;
                case SNDRV_PCM_STATE_DRAINING:
                        if (is_playback)
                                err = -EPIPE;
                        else 
                                avail = 0; /* indicate draining */
                        goto _endloop;
                case SNDRV_PCM_STATE_OPEN:
                case SNDRV_PCM_STATE_SETUP:
                case SNDRV_PCM_STATE_DISCONNECTED:
                        err = -EBADFD;
                        goto _endloop;
                case SNDRV_PCM_STATE_PAUSED:
                        continue;
                }
                if (!tout) {
                        pcm_dbg(substream->pcm,
                                "%s timeout (DMA or IRQ trouble?)\n",
                                is_playback ? "playback write" : "capture read");
                        err = -EIO;
                        break;
                }
        }
 _endloop:
        set_current_state(TASK_RUNNING);
        remove_wait_queue(&runtime->tsleep, &wait);
        *availp = avail;
        return err;
}
        
typedef int (*pcm_transfer_f)(struct snd_pcm_substream *substream,
                              int channel, unsigned long hwoff,
                              void *buf, unsigned long bytes);

typedef int (*pcm_copy_f)(struct snd_pcm_substream *, snd_pcm_uframes_t, void *,
                          snd_pcm_uframes_t, snd_pcm_uframes_t, pcm_transfer_f);

/* calculate the target DMA-buffer position to be written/read */
static void *get_dma_ptr(struct snd_pcm_runtime *runtime,
                           int channel, unsigned long hwoff)
{
        return runtime->dma_area + hwoff +
                channel * (runtime->dma_bytes / runtime->channels);
}

/* default copy_user ops for write; used for both interleaved and non- modes */
static int default_write_copy(struct snd_pcm_substream *substream,
                              int channel, unsigned long hwoff,
                              void *buf, unsigned long bytes)
{
        if (copy_from_user(get_dma_ptr(substream->runtime, channel, hwoff),
                           (void __user *)buf, bytes))
                return -EFAULT;
        return 0;
}

/* default copy_kernel ops for write */
static int default_write_copy_kernel(struct snd_pcm_substream *substream,
                                     int channel, unsigned long hwoff,
                                     void *buf, unsigned long bytes)
{
        memcpy(get_dma_ptr(substream->runtime, channel, hwoff), buf, bytes);
        return 0;
}

/* fill silence instead of copy data; called as a transfer helper
 * from __snd_pcm_lib_write() or directly from noninterleaved_copy() when
 * a NULL buffer is passed
 */
static int fill_silence(struct snd_pcm_substream *substream, int channel,
                        unsigned long hwoff, void *buf, unsigned long bytes)
{
        struct snd_pcm_runtime *runtime = substream->runtime;

        if (substream->stream != SNDRV_PCM_STREAM_PLAYBACK)
                return 0;
        if (substream->ops->fill_silence)
                return substream->ops->fill_silence(substream, channel,
                                                    hwoff, bytes);

        snd_pcm_format_set_silence(runtime->format,
                                   get_dma_ptr(runtime, channel, hwoff),
                                   bytes_to_samples(runtime, bytes));
        return 0;
}

/* default copy_user ops for read; used for both interleaved and non- modes */
static int default_read_copy(struct snd_pcm_substream *substream,
                             int channel, unsigned long hwoff,
                             void *buf, unsigned long bytes)
{
        if (copy_to_user((void __user *)buf,
                         get_dma_ptr(substream->runtime, channel, hwoff),
                         bytes))
                return -EFAULT;
        return 0;
}

/* default copy_kernel ops for read */
static int default_read_copy_kernel(struct snd_pcm_substream *substream,
                                    int channel, unsigned long hwoff,
                                    void *buf, unsigned long bytes)
{
        memcpy(buf, get_dma_ptr(substream->runtime, channel, hwoff), bytes);
        return 0;
}

/* call transfer function with the converted pointers and sizes;
 * for interleaved mode, it's one shot for all samples
 */
static int interleaved_copy(struct snd_pcm_substream *substream,
                            snd_pcm_uframes_t hwoff, void *data,
                            snd_pcm_uframes_t off,
                            snd_pcm_uframes_t frames,
                            pcm_transfer_f transfer)
{
        struct snd_pcm_runtime *runtime = substream->runtime;

        /* convert to bytes */
        hwoff = frames_to_bytes(runtime, hwoff);
        off = frames_to_bytes(runtime, off);
        frames = frames_to_bytes(runtime, frames);
        return transfer(substream, 0, hwoff, data + off, frames);
}

/* call transfer function with the converted pointers and sizes for each
 * non-interleaved channel; when buffer is NULL, silencing instead of copying
 */
static int noninterleaved_copy(struct snd_pcm_substream *substream,
                               snd_pcm_uframes_t hwoff, void *data,
                               snd_pcm_uframes_t off,
                               snd_pcm_uframes_t frames,
                               pcm_transfer_f transfer)
{
        struct snd_pcm_runtime *runtime = substream->runtime;
        int channels = runtime->channels;
        void **bufs = data;
        int c, err;

        /* convert to bytes; note that it's not frames_to_bytes() here.
         * in non-interleaved mode, we copy for each channel, thus
         * each copy is n_samples bytes x channels = whole frames.
         */
        off = samples_to_bytes(runtime, off);
        frames = samples_to_bytes(runtime, frames);
        hwoff = samples_to_bytes(runtime, hwoff);
        for (c = 0; c < channels; ++c, ++bufs) {
                if (!data || !*bufs)
                        err = fill_silence(substream, c, hwoff, NULL, frames);
                else
                        err = transfer(substream, c, hwoff, *bufs + off,
                                       frames);
                if (err < 0)
                        return err;
        }
        return 0;
}

/* fill silence on the given buffer position;
 * called from snd_pcm_playback_silence()
 */
static int fill_silence_frames(struct snd_pcm_substream *substream,
                               snd_pcm_uframes_t off, snd_pcm_uframes_t frames)
{
        if (substream->runtime->access == SNDRV_PCM_ACCESS_RW_INTERLEAVED ||
            substream->runtime->access == SNDRV_PCM_ACCESS_MMAP_INTERLEAVED)
                return interleaved_copy(substream, off, NULL, 0, frames,
                                        fill_silence);
        else
                return noninterleaved_copy(substream, off, NULL, 0, frames,
                                           fill_silence);
}

/* sanity-check for read/write methods */
static int pcm_sanity_check(struct snd_pcm_substream *substream)
{
        struct snd_pcm_runtime *runtime;
        if (PCM_RUNTIME_CHECK(substream))
                return -ENXIO;
        runtime = substream->runtime;
        if (snd_BUG_ON(!substream->ops->copy_user && !runtime->dma_area))
                return -EINVAL;
        if (runtime->state == SNDRV_PCM_STATE_OPEN)
                return -EBADFD;
        return 0;
}

static int pcm_accessible_state(struct snd_pcm_runtime *runtime)
{
        switch (runtime->state) {
        case SNDRV_PCM_STATE_PREPARED:
        case SNDRV_PCM_STATE_RUNNING:
        case SNDRV_PCM_STATE_PAUSED:
                return 0;
        case SNDRV_PCM_STATE_XRUN:
                return -EPIPE;
        case SNDRV_PCM_STATE_SUSPENDED:
                return -ESTRPIPE;
        default:
                return -EBADFD;
        }
}

/* update to the given appl_ptr and call ack callback if needed;
 * when an error is returned, take back to the original value
 */
int pcm_lib_apply_appl_ptr(struct snd_pcm_substream *substream,
                           snd_pcm_uframes_t appl_ptr)
{
        struct snd_pcm_runtime *runtime = substream->runtime;
        snd_pcm_uframes_t old_appl_ptr = runtime->control->appl_ptr;
        snd_pcm_sframes_t diff;
        int ret;

        if (old_appl_ptr == appl_ptr)
                return 0;

        if (appl_ptr >= runtime->boundary)
                return -EINVAL;
        /*
         * check if a rewind is requested by the application
         */
        if (substream->runtime->info & SNDRV_PCM_INFO_NO_REWINDS) {
                diff = appl_ptr - old_appl_ptr;
                if (diff >= 0) {
                        if (diff > runtime->buffer_size)
                                return -EINVAL;
                } else {
                        if (runtime->boundary + diff > runtime->buffer_size)
                                return -EINVAL;
                }
        }

        runtime->control->appl_ptr = appl_ptr;
        if (substream->ops->ack) {
                ret = substream->ops->ack(substream);
                if (ret < 0) {
                        runtime->control->appl_ptr = old_appl_ptr;
                        if (ret == -EPIPE)
                                __snd_pcm_xrun(substream);
                        return ret;
                }
        }

        trace_applptr(substream, old_appl_ptr, appl_ptr);

        return 0;
}

/* the common loop for read/write data */
snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream,
                                     void *data, bool interleaved,
                                     snd_pcm_uframes_t size, bool in_kernel)
{
        struct snd_pcm_runtime *runtime = substream->runtime;
        snd_pcm_uframes_t xfer = 0;
        snd_pcm_uframes_t offset = 0;
        snd_pcm_uframes_t avail;
        pcm_copy_f writer;
        pcm_transfer_f transfer;
        bool nonblock;
        bool is_playback;
        int err;

        err = pcm_sanity_check(substream);
        if (err < 0)
                return err;

        is_playback = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
        if (interleaved) {
                if (runtime->access != SNDRV_PCM_ACCESS_RW_INTERLEAVED &&
                    runtime->channels > 1)
                        return -EINVAL;
                writer = interleaved_copy;
        } else {
                if (runtime->access != SNDRV_PCM_ACCESS_RW_NONINTERLEAVED)
                        return -EINVAL;
                writer = noninterleaved_copy;
        }

        if (!data) {
                if (is_playback)
                        transfer = fill_silence;
                else
                        return -EINVAL;
        } else if (in_kernel) {
                if (substream->ops->copy_kernel)
                        transfer = substream->ops->copy_kernel;
                else
                        transfer = is_playback ?
                                default_write_copy_kernel : default_read_copy_kernel;
        } else {
                if (substream->ops->copy_user)
                        transfer = (pcm_transfer_f)substream->ops->copy_user;
                else
                        transfer = is_playback ?
                                default_write_copy : default_read_copy;
        }

        if (size == 0)
                return 0;

        nonblock = !!(substream->f_flags & O_NONBLOCK);

        snd_pcm_stream_lock_irq(substream);
        err = pcm_accessible_state(runtime);
        if (err < 0)
                goto _end_unlock;

        runtime->twake = runtime->control->avail_min ? : 1;
        if (runtime->state == SNDRV_PCM_STATE_RUNNING)
                snd_pcm_update_hw_ptr(substream);

        /*
         * If size < start_threshold, wait indefinitely. Another
         * thread may start capture
         */
        if (!is_playback &&
            runtime->state == SNDRV_PCM_STATE_PREPARED &&
            size >= runtime->start_threshold) {
                err = snd_pcm_start(substream);
                if (err < 0)
                        goto _end_unlock;
        }

        avail = snd_pcm_avail(substream);

        while (size > 0) {
                snd_pcm_uframes_t frames, appl_ptr, appl_ofs;
                snd_pcm_uframes_t cont;
                if (!avail) {
                        if (!is_playback &&
                            runtime->state == SNDRV_PCM_STATE_DRAINING) {
                                snd_pcm_stop(substream, SNDRV_PCM_STATE_SETUP);
                                goto _end_unlock;
                        }
                        if (nonblock) {
                                err = -EAGAIN;
                                goto _end_unlock;
                        }
                        runtime->twake = min_t(snd_pcm_uframes_t, size,
                                        runtime->control->avail_min ? : 1);
                        err = wait_for_avail(substream, &avail);
                        if (err < 0)
                                goto _end_unlock;
                        if (!avail)
                                continue; /* draining */
                }
                frames = size > avail ? avail : size;
                appl_ptr = READ_ONCE(runtime->control->appl_ptr);
                appl_ofs = appl_ptr % runtime->buffer_size;
                cont = runtime->buffer_size - appl_ofs;
                if (frames > cont)
                        frames = cont;
                if (snd_BUG_ON(!frames)) {
                        err = -EINVAL;
                        goto _end_unlock;
                }
                if (!atomic_inc_unless_negative(&runtime->buffer_accessing)) {
                        err = -EBUSY;
                        goto _end_unlock;
                }
                snd_pcm_stream_unlock_irq(substream);
                if (!is_playback)
                        snd_pcm_dma_buffer_sync(substream, SNDRV_DMA_SYNC_CPU);
                err = writer(substream, appl_ofs, data, offset, frames,
                             transfer);
                if (is_playback)
                        snd_pcm_dma_buffer_sync(substream, SNDRV_DMA_SYNC_DEVICE);
                snd_pcm_stream_lock_irq(substream);
                atomic_dec(&runtime->buffer_accessing);
                if (err < 0)
                        goto _end_unlock;
                err = pcm_accessible_state(runtime);
                if (err < 0)
                        goto _end_unlock;
                appl_ptr += frames;
                if (appl_ptr >= runtime->boundary)
                        appl_ptr -= runtime->boundary;
                err = pcm_lib_apply_appl_ptr(substream, appl_ptr);
                if (err < 0)
                        goto _end_unlock;

                offset += frames;
                size -= frames;
                xfer += frames;
                avail -= frames;
                if (is_playback &&
                    runtime->state == SNDRV_PCM_STATE_PREPARED &&
                    snd_pcm_playback_hw_avail(runtime) >= (snd_pcm_sframes_t)runtime->start_threshold) {
                        err = snd_pcm_start(substream);
                        if (err < 0)
                                goto _end_unlock;
                }
        }
 _end_unlock:
        runtime->twake = 0;
        if (xfer > 0 && err >= 0)
                snd_pcm_update_state(substream, runtime);
        snd_pcm_stream_unlock_irq(substream);
        return xfer > 0 ? (snd_pcm_sframes_t)xfer : err;
}
EXPORT_SYMBOL(__snd_pcm_lib_xfer);

/*
 * standard channel mapping helpers
 */

/* default channel maps for multi-channel playbacks, up to 8 channels */
const struct snd_pcm_chmap_elem snd_pcm_std_chmaps[] = {
        { .channels = 1,
          .map = { SNDRV_CHMAP_MONO } },
        { .channels = 2,
          .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR } },
        { .channels = 4,
          .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
                   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR } },
        { .channels = 6,
          .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
                   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR,
                   SNDRV_CHMAP_FC, SNDRV_CHMAP_LFE } },
        { .channels = 8,
          .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
                   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR,
                   SNDRV_CHMAP_FC, SNDRV_CHMAP_LFE,
                   SNDRV_CHMAP_SL, SNDRV_CHMAP_SR } },
        { }
};
EXPORT_SYMBOL_GPL(snd_pcm_std_chmaps);

/* alternative channel maps with CLFE <-> surround swapped for 6/8 channels */
const struct snd_pcm_chmap_elem snd_pcm_alt_chmaps[] = {
        { .channels = 1,
          .map = { SNDRV_CHMAP_MONO } },
        { .channels = 2,
          .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR } },
        { .channels = 4,
          .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
                   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR } },
        { .channels = 6,
          .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
                   SNDRV_CHMAP_FC, SNDRV_CHMAP_LFE,
                   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR } },
        { .channels = 8,
          .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
                   SNDRV_CHMAP_FC, SNDRV_CHMAP_LFE,
                   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR,
                   SNDRV_CHMAP_SL, SNDRV_CHMAP_SR } },
        { }
};
EXPORT_SYMBOL_GPL(snd_pcm_alt_chmaps);

static bool valid_chmap_channels(const struct snd_pcm_chmap *info, int ch)
{
        if (ch > info->max_channels)
                return false;
        return !info->channel_mask || (info->channel_mask & (1U << ch));
}

static int pcm_chmap_ctl_info(struct snd_kcontrol *kcontrol,
                              struct snd_ctl_elem_info *uinfo)
{
        struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol);

        uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
        uinfo->count = info->max_channels;
        uinfo->value.integer.min = 0;
        uinfo->value.integer.max = SNDRV_CHMAP_LAST;
        return 0;
}

/* get callback for channel map ctl element
 * stores the channel position firstly matching with the current channels
 */
static int pcm_chmap_ctl_get(struct snd_kcontrol *kcontrol,
                             struct snd_ctl_elem_value *ucontrol)
{
        struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol);
        unsigned int idx = snd_ctl_get_ioffidx(kcontrol, &ucontrol->id);
        struct snd_pcm_substream *substream;
        const struct snd_pcm_chmap_elem *map;

        if (!info->chmap)
                return -EINVAL;
        substream = snd_pcm_chmap_substream(info, idx);
        if (!substream)
                return -ENODEV;
        memset(ucontrol->value.integer.value, 0,
               sizeof(long) * info->max_channels);
        if (!substream->runtime)
                return 0; /* no channels set */
        for (map = info->chmap; map->channels; map++) {
                int i;
                if (map->channels == substream->runtime->channels &&
                    valid_chmap_channels(info, map->channels)) {
                        for (i = 0; i < map->channels; i++)
                                ucontrol->value.integer.value[i] = map->map[i];
                        return 0;
                }
        }
        return -EINVAL;
}

/* tlv callback for channel map ctl element
 * expands the pre-defined channel maps in a form of TLV
 */
static int pcm_chmap_ctl_tlv(struct snd_kcontrol *kcontrol, int op_flag,
                             unsigned int size, unsigned int __user *tlv)
{
        struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol);
        const struct snd_pcm_chmap_elem *map;
        unsigned int __user *dst;
        int c, count = 0;

        if (!info->chmap)
                return -EINVAL;
        if (size < 8)
                return -ENOMEM;
        if (put_user(SNDRV_CTL_TLVT_CONTAINER, tlv))
                return -EFAULT;
        size -= 8;
        dst = tlv + 2;
        for (map = info->chmap; map->channels; map++) {
                int chs_bytes = map->channels * 4;
                if (!valid_chmap_channels(info, map->channels))
                        continue;
                if (size < 8)
                        return -ENOMEM;
                if (put_user(SNDRV_CTL_TLVT_CHMAP_FIXED, dst) ||
                    put_user(chs_bytes, dst + 1))
                        return -EFAULT;
                dst += 2;
                size -= 8;
                count += 8;
                if (size < chs_bytes)
                        return -ENOMEM;
                size -= chs_bytes;
                count += chs_bytes;
                for (c = 0; c < map->channels; c++) {
                        if (put_user(map->map[c], dst))
                                return -EFAULT;
                        dst++;
                }
        }
        if (put_user(count, tlv + 1))
                return -EFAULT;
        return 0;
}

static void pcm_chmap_ctl_private_free(struct snd_kcontrol *kcontrol)
{
        struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol);
        info->pcm->streams[info->stream].chmap_kctl = NULL;
        kfree(info);
}

/**
 * snd_pcm_add_chmap_ctls - create channel-mapping control elements
 * @pcm: the assigned PCM instance
 * @stream: stream direction
 * @chmap: channel map elements (for query)
 * @max_channels: the max number of channels for the stream
 * @private_value: the value passed to each kcontrol's private_value field
 * @info_ret: store struct snd_pcm_chmap instance if non-NULL
 *
 * Create channel-mapping control elements assigned to the given PCM stream(s).
 * Return: Zero if successful, or a negative error value.
 */
int snd_pcm_add_chmap_ctls(struct snd_pcm *pcm, int stream,
                           const struct snd_pcm_chmap_elem *chmap,
                           int max_channels,
                           unsigned long private_value,
                           struct snd_pcm_chmap **info_ret)
{
        struct snd_pcm_chmap *info;
        struct snd_kcontrol_new knew = {
                .iface = SNDRV_CTL_ELEM_IFACE_PCM,
                .access = SNDRV_CTL_ELEM_ACCESS_READ |
                        SNDRV_CTL_ELEM_ACCESS_TLV_READ |
                        SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK,
                .info = pcm_chmap_ctl_info,
                .get = pcm_chmap_ctl_get,
                .tlv.c = pcm_chmap_ctl_tlv,
        };
        int err;

        if (WARN_ON(pcm->streams[stream].chmap_kctl))
                return -EBUSY;
        info = kzalloc(sizeof(*info), GFP_KERNEL);
        if (!info)
                return -ENOMEM;
        info->pcm = pcm;
        info->stream = stream;
        info->chmap = chmap;
        info->max_channels = max_channels;
        if (stream == SNDRV_PCM_STREAM_PLAYBACK)
                knew.name = "Playback Channel Map";
        else
                knew.name = "Capture Channel Map";
        knew.device = pcm->device;
        knew.count = pcm->streams[stream].substream_count;
        knew.private_value = private_value;
        info->kctl = snd_ctl_new1(&knew, info);
        if (!info->kctl) {
                kfree(info);
                return -ENOMEM;
        }
        info->kctl->private_free = pcm_chmap_ctl_private_free;
        err = snd_ctl_add(pcm->card, info->kctl);
        if (err < 0)
                return err;
        pcm->streams[stream].chmap_kctl = info->kctl;
        if (info_ret)
                *info_ret = info;
        return 0;
}
EXPORT_SYMBOL_GPL(snd_pcm_add_chmap_ctls);