+++ /dev/null
-/* The industrial I/O simple minimally locked ring buffer.
- *
- * Copyright (c) 2008 Jonathan Cameron
- *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License version 2 as published by
- * the Free Software Foundation.
- */
-
-#include <linux/slab.h>
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/device.h>
-#include <linux/workqueue.h>
-#include <linux/sched.h>
-#include <linux/poll.h>
-#include "ring_sw.h"
-#include <linux/iio/trigger.h>
-
-/**
- * struct iio_sw_ring_buffer - software ring buffer
- * @buf: generic ring buffer elements
- * @data: the ring buffer memory
- * @read_p: read pointer (oldest available)
- * @write_p: write pointer
- * @half_p: half buffer length behind write_p (event generation)
- * @update_needed: flag to indicate change in size requested
- *
- * Note that the first element of all ring buffers must be a
- * struct iio_buffer.
-**/
-struct iio_sw_ring_buffer {
- struct iio_buffer buf;
- unsigned char *data;
- unsigned char *read_p;
- unsigned char *write_p;
- /* used to act as a point at which to signal an event */
- unsigned char *half_p;
- int update_needed;
-};
-
-#define iio_to_sw_ring(r) container_of(r, struct iio_sw_ring_buffer, buf)
-
-static inline int __iio_allocate_sw_ring_buffer(struct iio_sw_ring_buffer *ring,
- int bytes_per_datum, int length)
-{
- if ((length == 0) || (bytes_per_datum == 0))
- return -EINVAL;
- __iio_update_buffer(&ring->buf, bytes_per_datum, length);
- ring->data = kmalloc(length*ring->buf.bytes_per_datum, GFP_ATOMIC);
- ring->read_p = NULL;
- ring->write_p = NULL;
- ring->half_p = NULL;
- return ring->data ? 0 : -ENOMEM;
-}
-
-static inline void __iio_free_sw_ring_buffer(struct iio_sw_ring_buffer *ring)
-{
- kfree(ring->data);
-}
-
-/* Ring buffer related functionality */
-/* Store to ring is typically called in the bh of a data ready interrupt handler
- * in the device driver */
-/* Lock always held if their is a chance this may be called */
-/* Only one of these per ring may run concurrently - enforced by drivers */
-static int iio_store_to_sw_ring(struct iio_sw_ring_buffer *ring,
- unsigned char *data)
-{
- int ret = 0;
- unsigned char *temp_ptr, *change_test_ptr;
-
- /* initial store */
- if (unlikely(ring->write_p == NULL)) {
- ring->write_p = ring->data;
- /* Doesn't actually matter if this is out of the set
- * as long as the read pointer is valid before this
- * passes it - guaranteed as set later in this function.
- */
- ring->half_p = ring->data - ring->buf.length*ring->buf.bytes_per_datum/2;
- }
- /* Copy data to where ever the current write pointer says */
- memcpy(ring->write_p, data, ring->buf.bytes_per_datum);
- barrier();
- /* Update the pointer used to get most recent value.
- * Always valid as either points to latest or second latest value.
- * Before this runs it is null and read attempts fail with -EAGAIN.
- */
- barrier();
- /* temp_ptr used to ensure we never have an invalid pointer
- * it may be slightly lagging, but never invalid
- */
- temp_ptr = ring->write_p + ring->buf.bytes_per_datum;
- /* End of ring, back to the beginning */
- if (temp_ptr == ring->data + ring->buf.length*ring->buf.bytes_per_datum)
- temp_ptr = ring->data;
- /* Update the write pointer
- * always valid as long as this is the only function able to write.
- * Care needed with smp systems to ensure more than one ring fill
- * is never scheduled.
- */
- ring->write_p = temp_ptr;
-
- if (ring->read_p == NULL)
- ring->read_p = ring->data;
- /* Buffer full - move the read pointer and create / escalate
- * ring event */
- /* Tricky case - if the read pointer moves before we adjust it.
- * Handle by not pushing if it has moved - may result in occasional
- * unnecessary buffer full events when it wasn't quite true.
- */
- else if (ring->write_p == ring->read_p) {
- change_test_ptr = ring->read_p;
- temp_ptr = change_test_ptr + ring->buf.bytes_per_datum;
- if (temp_ptr
- == ring->data + ring->buf.length*ring->buf.bytes_per_datum) {
- temp_ptr = ring->data;
- }
- /* We are moving pointer on one because the ring is full. Any
- * change to the read pointer will be this or greater.
- */
- if (change_test_ptr == ring->read_p)
- ring->read_p = temp_ptr;
- }
- /* investigate if our event barrier has been passed */
- /* There are definite 'issues' with this and chances of
- * simultaneous read */
- /* Also need to use loop count to ensure this only happens once */
- ring->half_p += ring->buf.bytes_per_datum;
- if (ring->half_p == ring->data + ring->buf.length*ring->buf.bytes_per_datum)
- ring->half_p = ring->data;
- if (ring->half_p == ring->read_p) {
- ring->buf.stufftoread = true;
- wake_up_interruptible(&ring->buf.pollq);
- }
- return ret;
-}
-
-static int iio_read_first_n_sw_rb(struct iio_buffer *r,
- size_t n, char __user *buf)
-{
- struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
-
- u8 *initial_read_p, *initial_write_p, *current_read_p, *end_read_p;
- u8 *data;
- int ret, max_copied, bytes_to_rip, dead_offset;
- size_t data_available, buffer_size;
-
- /* A userspace program has probably made an error if it tries to
- * read something that is not a whole number of bpds.
- * Return an error.
- */
- if (n % ring->buf.bytes_per_datum) {
- ret = -EINVAL;
- printk(KERN_INFO "Ring buffer read request not whole number of"
- "samples: Request bytes %zd, Current bytes per datum %d\n",
- n, ring->buf.bytes_per_datum);
- goto error_ret;
- }
-
- buffer_size = ring->buf.bytes_per_datum*ring->buf.length;
-
- /* Limit size to whole of ring buffer */
- bytes_to_rip = min_t(size_t, buffer_size, n);
-
- data = kmalloc(bytes_to_rip, GFP_KERNEL);
- if (data == NULL) {
- ret = -ENOMEM;
- goto error_ret;
- }
-
- /* build local copy */
- initial_read_p = ring->read_p;
- if (unlikely(initial_read_p == NULL)) { /* No data here as yet */
- ret = 0;
- goto error_free_data_cpy;
- }
-
- initial_write_p = ring->write_p;
-
- /* Need a consistent pair */
- while ((initial_read_p != ring->read_p)
- || (initial_write_p != ring->write_p)) {
- initial_read_p = ring->read_p;
- initial_write_p = ring->write_p;
- }
- if (initial_write_p == initial_read_p) {
- /* No new data available.*/
- ret = 0;
- goto error_free_data_cpy;
- }
-
- if (initial_write_p >= initial_read_p)
- data_available = initial_write_p - initial_read_p;
- else
- data_available = buffer_size - (initial_read_p - initial_write_p);
-
- if (data_available < bytes_to_rip)
- bytes_to_rip = data_available;
-
- if (initial_read_p + bytes_to_rip >= ring->data + buffer_size) {
- max_copied = ring->data + buffer_size - initial_read_p;
- memcpy(data, initial_read_p, max_copied);
- memcpy(data + max_copied, ring->data, bytes_to_rip - max_copied);
- end_read_p = ring->data + bytes_to_rip - max_copied;
- } else {
- memcpy(data, initial_read_p, bytes_to_rip);
- end_read_p = initial_read_p + bytes_to_rip;
- }
-
- /* Now to verify which section was cleanly copied - i.e. how far
- * read pointer has been pushed */
- current_read_p = ring->read_p;
-
- if (initial_read_p <= current_read_p)
- dead_offset = current_read_p - initial_read_p;
- else
- dead_offset = buffer_size - (initial_read_p - current_read_p);
-
- /* possible issue if the initial write has been lapped or indeed
- * the point we were reading to has been passed */
- /* No valid data read.
- * In this case the read pointer is already correct having been
- * pushed further than we would look. */
- if (bytes_to_rip - dead_offset < 0) {
- ret = 0;
- goto error_free_data_cpy;
- }
-
- /* setup the next read position */
- /* Beware, this may fail due to concurrency fun and games.
- * Possible that sufficient fill commands have run to push the read
- * pointer past where we would be after the rip. If this occurs, leave
- * it be.
- */
- /* Tricky - deal with loops */
-
- while (ring->read_p != end_read_p)
- ring->read_p = end_read_p;
-
- ret = bytes_to_rip - dead_offset;
-
- if (copy_to_user(buf, data + dead_offset, ret)) {
- ret = -EFAULT;
- goto error_free_data_cpy;
- }
-
- if (bytes_to_rip >= ring->buf.length*ring->buf.bytes_per_datum/2)
- ring->buf.stufftoread = 0;
-
-error_free_data_cpy:
- kfree(data);
-error_ret:
-
- return ret;
-}
-
-static int iio_store_to_sw_rb(struct iio_buffer *r,
- u8 *data)
-{
- struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
- return iio_store_to_sw_ring(ring, data);
-}
-
-static int iio_request_update_sw_rb(struct iio_buffer *r)
-{
- int ret = 0;
- struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
-
- r->stufftoread = false;
- if (!ring->update_needed)
- goto error_ret;
- __iio_free_sw_ring_buffer(ring);
- ret = __iio_allocate_sw_ring_buffer(ring, ring->buf.bytes_per_datum,
- ring->buf.length);
-error_ret:
- return ret;
-}
-
-static int iio_get_bytes_per_datum_sw_rb(struct iio_buffer *r)
-{
- struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
- return ring->buf.bytes_per_datum;
-}
-
-static int iio_mark_update_needed_sw_rb(struct iio_buffer *r)
-{
- struct iio_sw_ring_buffer *ring = iio_to_sw_ring(r);
- ring->update_needed = true;
- return 0;
-}
-
-static int iio_set_bytes_per_datum_sw_rb(struct iio_buffer *r, size_t bpd)
-{
- if (r->bytes_per_datum != bpd) {
- r->bytes_per_datum = bpd;
- iio_mark_update_needed_sw_rb(r);
- }
- return 0;
-}
-
-static int iio_get_length_sw_rb(struct iio_buffer *r)
-{
- return r->length;
-}
-
-static int iio_set_length_sw_rb(struct iio_buffer *r, int length)
-{
- if (r->length != length) {
- r->length = length;
- iio_mark_update_needed_sw_rb(r);
- }
- return 0;
-}
-
-static IIO_BUFFER_ENABLE_ATTR;
-static IIO_BUFFER_LENGTH_ATTR;
-
-/* Standard set of ring buffer attributes */
-static struct attribute *iio_ring_attributes[] = {
- &dev_attr_length.attr,
- &dev_attr_enable.attr,
- NULL,
-};
-
-static struct attribute_group iio_ring_attribute_group = {
- .attrs = iio_ring_attributes,
- .name = "buffer",
-};
-
-static const struct iio_buffer_access_funcs ring_sw_access_funcs = {
- .store_to = &iio_store_to_sw_rb,
- .read_first_n = &iio_read_first_n_sw_rb,
- .request_update = &iio_request_update_sw_rb,
- .get_bytes_per_datum = &iio_get_bytes_per_datum_sw_rb,
- .set_bytes_per_datum = &iio_set_bytes_per_datum_sw_rb,
- .get_length = &iio_get_length_sw_rb,
- .set_length = &iio_set_length_sw_rb,
-};
-
-struct iio_buffer *iio_sw_rb_allocate(struct iio_dev *indio_dev)
-{
- struct iio_buffer *buf;
- struct iio_sw_ring_buffer *ring;
-
- ring = kzalloc(sizeof *ring, GFP_KERNEL);
- if (!ring)
- return NULL;
- ring->update_needed = true;
- buf = &ring->buf;
- iio_buffer_init(buf);
- buf->attrs = &iio_ring_attribute_group;
- buf->access = &ring_sw_access_funcs;
-
- return buf;
-}
-EXPORT_SYMBOL(iio_sw_rb_allocate);
-
-void iio_sw_rb_free(struct iio_buffer *r)
-{
- kfree(iio_to_sw_ring(r));
-}
-EXPORT_SYMBOL(iio_sw_rb_free);
-
-MODULE_DESCRIPTION("Industrial I/O software ring buffer");
-MODULE_LICENSE("GPL");
projects / platform / kernel / linux-rpi.git / commitdiff