ALSA: firewire-lib: code refactoring for syt offset calculation

When calculating syt offset, some states are stored in AMDTP stream
structure. This is inconvenient when reuse the calculation from
non-stream structure.

This commit applies refactoring to helper function for the calculation
so that the function doesn't touch AMDTP stream structure.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20200508043635.349339-7-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/firewire/amdtp-stream.c b/sound/firewire/amdtp-stream.c
index 1605ea4..9041510 100644 (file)
--- a/sound/firewire/amdtp-stream.c
+++ b/sound/firewire/amdtp-stream.c
@@ -383,14 +383,14 @@ static unsigned int calculate_data_blocks(struct amdtp_stream *s,
        return data_blocks;
 }
 
-static unsigned int calculate_syt_offset(struct amdtp_stream *s)
+static unsigned int calculate_syt_offset(unsigned int *last_syt_offset,
+                       unsigned int *syt_offset_state, enum cip_sfc sfc)
 {
-       unsigned int syt_offset, phase, index;
+       unsigned int syt_offset;
 
-       if (s->ctx_data.rx.last_syt_offset < TICKS_PER_CYCLE) {
-               if (!cip_sfc_is_base_44100(s->sfc))
-                       syt_offset = s->ctx_data.rx.last_syt_offset +
-                                    s->ctx_data.rx.syt_offset_state;
+       if (*last_syt_offset < TICKS_PER_CYCLE) {
+               if (!cip_sfc_is_base_44100(sfc))
+                       syt_offset = *last_syt_offset + *syt_offset_state;
                else {
                /*
                 * The time, in ticks, of the n'th SYT_INTERVAL sample is:
@@ -402,18 +402,19 @@ static unsigned int calculate_syt_offset(struct amdtp_stream *s)
                 *   1386 1386 1387 1386 1386 1386 1387 1386 1386 1386 1387 ...
                 * This code generates _exactly_ the same sequence.
                 */
-                       phase = s->ctx_data.rx.syt_offset_state;
-                       index = phase % 13;
-                       syt_offset = s->ctx_data.rx.last_syt_offset;
+                       unsigned int phase = *syt_offset_state;
+                       unsigned int index = phase % 13;
+
+                       syt_offset = *last_syt_offset;
                        syt_offset += 1386 + ((index && !(index & 3)) ||
                                              phase == 146);
                        if (++phase >= 147)
                                phase = 0;
-                       s->ctx_data.rx.syt_offset_state = phase;
+                       *syt_offset_state = phase;
                }
        } else
-               syt_offset = s->ctx_data.rx.last_syt_offset - TICKS_PER_CYCLE;
-       s->ctx_data.rx.last_syt_offset = syt_offset;
+               syt_offset = *last_syt_offset - TICKS_PER_CYCLE;
+       *last_syt_offset = syt_offset;
 
        if (syt_offset >= TICKS_PER_CYCLE)
                syt_offset = CIP_SYT_NO_INFO;
@@ -759,7 +760,9 @@ static void generate_ideal_pkt_descs(struct amdtp_stream *s,
                unsigned int syt_offset;
 
                desc->cycle = compute_it_cycle(*ctx_header, s->queue_size);
-               syt_offset = calculate_syt_offset(s);
+               syt_offset = calculate_syt_offset(
+                               &s->ctx_data.rx.last_syt_offset,
+                               &s->ctx_data.rx.syt_offset_state, s->sfc);
                if (syt_offset != CIP_SYT_NO_INFO) {
                        desc->syt = compute_syt(syt_offset, desc->cycle,
                                                s->ctx_data.rx.transfer_delay);