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https://github.com/alsa-project/alsa-utils
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cd211d8c22
There're several types of system calls for multiplexed I/O. They're used to receive notifications of I/O events. Typically, userspace applications call them against file descriptor to yield CPU. When I/O is enabled on any of the descriptors, a task of the application is rescheduled, then the application execute I/O calls. This commit adds a common interface for this type of system calls, named as 'waiter'. This is expected to be used with non-blocking file operation and operations on mapped page frame. Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp> Signed-off-by: Takashi Iwai <tiwai@suse.de>
427 lines
11 KiB
C
427 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0
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//
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// xfer-libasound-irq-rw.c - IRQ-based scheduling model for read/write operation.
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//
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// Copyright (c) 2018 Takashi Sakamoto <o-takashi@sakamocchi.jp>
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//
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// Licensed under the terms of the GNU General Public License, version 2.
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#include "xfer-libasound.h"
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#include "misc.h"
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#include "frame-cache.h"
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struct rw_closure {
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snd_pcm_access_t access;
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int (*process_frames)(struct libasound_state *state,
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snd_pcm_state_t status, unsigned int *frame_count,
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struct mapper_context *mapper,
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struct container_context *cntrs);
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struct frame_cache cache;
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};
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static int read_frames(struct libasound_state *state, unsigned int *frame_count,
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unsigned int avail_count, struct mapper_context *mapper,
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struct container_context *cntrs)
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{
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struct rw_closure *closure = state->private_data;
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snd_pcm_sframes_t handled_frame_count;
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unsigned int consumed_count;
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int err;
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// Trim according up to expected frame count.
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if (*frame_count < avail_count)
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avail_count = *frame_count;
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// Cache required amount of frames.
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if (avail_count > frame_cache_get_count(&closure->cache)) {
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avail_count -= frame_cache_get_count(&closure->cache);
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// Execute write operation according to the shape of buffer.
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// These operations automatically start the substream.
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if (closure->access == SND_PCM_ACCESS_RW_INTERLEAVED) {
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handled_frame_count = snd_pcm_readi(state->handle,
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closure->cache.buf_ptr,
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avail_count);
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} else {
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handled_frame_count = snd_pcm_readn(state->handle,
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closure->cache.buf_ptr,
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avail_count);
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}
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if (handled_frame_count < 0) {
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err = handled_frame_count;
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return err;
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}
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frame_cache_increase_count(&closure->cache, handled_frame_count);
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avail_count = frame_cache_get_count(&closure->cache);
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}
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// Write out to file descriptors.
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consumed_count = avail_count;
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err = mapper_context_process_frames(mapper, closure->cache.buf,
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&consumed_count, cntrs);
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if (err < 0)
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return err;
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frame_cache_reduce(&closure->cache, consumed_count);
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*frame_count = consumed_count;
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return 0;
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}
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static int r_process_frames_blocking(struct libasound_state *state,
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snd_pcm_state_t status,
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unsigned int *frame_count,
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struct mapper_context *mapper,
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struct container_context *cntrs)
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{
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snd_pcm_sframes_t avail;
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snd_pcm_uframes_t avail_count;
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int err = 0;
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if (status == SND_PCM_STATE_RUNNING) {
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// Check available space on the buffer.
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avail = snd_pcm_avail(state->handle);
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if (avail < 0) {
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err = avail;
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goto error;
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}
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avail_count = (snd_pcm_uframes_t)avail;
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if (avail_count == 0) {
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// Request data frames so that blocking is just
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// released.
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err = snd_pcm_sw_params_get_avail_min(state->sw_params,
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&avail_count);
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if (err < 0)
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goto error;
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}
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} else {
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// Request data frames so that the PCM substream starts.
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snd_pcm_uframes_t frame_count;
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err = snd_pcm_sw_params_get_start_threshold(state->sw_params,
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&frame_count);
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if (err < 0)
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goto error;
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avail_count = (unsigned int)frame_count;
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}
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err = read_frames(state, frame_count, avail_count, mapper, cntrs);
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if (err < 0)
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goto error;
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return 0;
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error:
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*frame_count = 0;
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return err;
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}
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static int r_process_frames_nonblocking(struct libasound_state *state,
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snd_pcm_state_t status,
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unsigned int *frame_count,
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struct mapper_context *mapper,
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struct container_context *cntrs)
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{
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snd_pcm_sframes_t avail;
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snd_pcm_uframes_t avail_count;
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int err = 0;
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if (status != SND_PCM_STATE_RUNNING) {
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err = snd_pcm_start(state->handle);
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if (err < 0)
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goto error;
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}
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if (state->use_waiter) {
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unsigned short revents;
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// Wait for hardware IRQ when no available space.
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err = xfer_libasound_wait_event(state, -1, &revents);
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if (err < 0)
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goto error;
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if (revents & POLLERR) {
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// TODO: error reporting.
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err = -EIO;
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goto error;
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}
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if (!(revents & POLLIN)) {
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err = -EAGAIN;
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goto error;
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}
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}
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// Check available space on the buffer.
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avail = snd_pcm_avail(state->handle);
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if (avail < 0) {
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err = avail;
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goto error;
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}
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avail_count = (snd_pcm_uframes_t)avail;
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if (avail_count == 0) {
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// Let's go to a next iteration.
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err = 0;
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goto error;
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}
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err = read_frames(state, frame_count, avail_count, mapper, cntrs);
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if (err < 0)
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goto error;
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return 0;
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error:
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*frame_count = 0;
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return err;
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}
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static int write_frames(struct libasound_state *state,
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unsigned int *frame_count, unsigned int avail_count,
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struct mapper_context *mapper,
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struct container_context *cntrs)
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{
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struct rw_closure *closure = state->private_data;
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snd_pcm_uframes_t consumed_count;
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snd_pcm_sframes_t handled_frame_count;
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int err;
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// Trim according up to expected frame count.
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if (*frame_count < avail_count)
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avail_count = *frame_count;
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// Cache required amount of frames.
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if (avail_count > frame_cache_get_count(&closure->cache)) {
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avail_count -= frame_cache_get_count(&closure->cache);
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// Read frames to transfer.
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err = mapper_context_process_frames(mapper,
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closure->cache.buf_ptr, &avail_count, cntrs);
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if (err < 0)
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return err;
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frame_cache_increase_count(&closure->cache, avail_count);
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avail_count = frame_cache_get_count(&closure->cache);
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}
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// Execute write operation according to the shape of buffer. These
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// operations automatically start the stream.
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consumed_count = avail_count;
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if (closure->access == SND_PCM_ACCESS_RW_INTERLEAVED) {
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handled_frame_count = snd_pcm_writei(state->handle,
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closure->cache.buf, consumed_count);
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} else {
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handled_frame_count = snd_pcm_writen(state->handle,
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closure->cache.buf, consumed_count);
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}
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if (handled_frame_count < 0) {
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err = handled_frame_count;
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return err;
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}
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consumed_count = handled_frame_count;
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frame_cache_reduce(&closure->cache, consumed_count);
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*frame_count = consumed_count;
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return 0;
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}
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static int w_process_frames_blocking(struct libasound_state *state,
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snd_pcm_state_t status,
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unsigned int *frame_count,
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struct mapper_context *mapper,
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struct container_context *cntrs)
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{
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snd_pcm_sframes_t avail;
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unsigned int avail_count;
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int err;
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if (status == SND_PCM_STATE_RUNNING) {
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// Check available space on the buffer.
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avail = snd_pcm_avail(state->handle);
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if (avail < 0) {
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err = avail;
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goto error;
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}
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avail_count = (unsigned int)avail;
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if (avail_count == 0) {
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// Fill with data frames so that blocking is just
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// released.
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snd_pcm_uframes_t avail_min;
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err = snd_pcm_sw_params_get_avail_min(state->sw_params,
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&avail_min);
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if (err < 0)
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goto error;
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avail_count = (unsigned int)avail_min;
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}
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} else {
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snd_pcm_uframes_t frames_for_start_threshold;
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snd_pcm_uframes_t frames_per_period;
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// Fill with data frames so that the PCM substream starts.
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err = snd_pcm_sw_params_get_start_threshold(state->sw_params,
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&frames_for_start_threshold);
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if (err < 0)
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goto error;
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// But the above number can be too small and cause XRUN because
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// I/O operation is done per period.
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err = snd_pcm_hw_params_get_period_size(state->hw_params,
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&frames_per_period, NULL);
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if (err < 0)
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goto error;
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// Use larger one to prevent from both of XRUN and successive
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// blocking.
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if (frames_for_start_threshold > frames_per_period)
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avail_count = (unsigned int)frames_for_start_threshold;
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else
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avail_count = (unsigned int)frames_per_period;
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}
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err = write_frames(state, frame_count, avail_count, mapper, cntrs);
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if (err < 0)
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goto error;
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return 0;
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error:
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*frame_count = 0;
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return err;
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}
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static int w_process_frames_nonblocking(struct libasound_state *state,
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snd_pcm_state_t status,
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unsigned int *frame_count,
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struct mapper_context *mapper,
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struct container_context *cntrs)
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{
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snd_pcm_sframes_t avail;
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unsigned int avail_count;
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int err;
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if (state->use_waiter) {
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unsigned short revents;
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// Wait for hardware IRQ when no left space.
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err = xfer_libasound_wait_event(state, -1, &revents);
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if (err < 0)
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goto error;
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if (revents & POLLERR) {
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// TODO: error reporting.
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err = -EIO;
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goto error;
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}
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if (!(revents & POLLOUT)) {
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err = -EAGAIN;
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goto error;
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}
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}
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// Check available space on the buffer.
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avail = snd_pcm_avail(state->handle);
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if (avail < 0) {
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err = avail;
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goto error;
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}
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avail_count = (unsigned int)avail;
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if (avail_count == 0) {
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// Let's go to a next iteration.
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err = 0;
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goto error;
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}
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err = write_frames(state, frame_count, avail_count, mapper, cntrs);
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if (err < 0)
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goto error;
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// NOTE: The substream starts automatically when the accumulated number
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// of queued data frame exceeds start_threshold.
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return 0;
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error:
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*frame_count = 0;
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return err;
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}
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static int irq_rw_pre_process(struct libasound_state *state)
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{
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struct rw_closure *closure = state->private_data;
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snd_pcm_format_t format;
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snd_pcm_uframes_t frames_per_buffer;
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int bytes_per_sample;
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unsigned int samples_per_frame;
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int err;
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err = snd_pcm_hw_params_get_format(state->hw_params, &format);
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if (err < 0)
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return err;
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bytes_per_sample = snd_pcm_format_physical_width(format) / 8;
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if (bytes_per_sample <= 0)
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return -ENXIO;
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err = snd_pcm_hw_params_get_channels(state->hw_params,
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&samples_per_frame);
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if (err < 0)
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return err;
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err = snd_pcm_hw_params_get_buffer_size(state->hw_params,
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&frames_per_buffer);
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if (err < 0)
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return err;
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err = snd_pcm_hw_params_get_access(state->hw_params, &closure->access);
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if (err < 0)
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return err;
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err = frame_cache_init(&closure->cache, closure->access,
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bytes_per_sample, samples_per_frame,
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frames_per_buffer);
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if (err < 0)
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return err;
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if (snd_pcm_stream(state->handle) == SND_PCM_STREAM_CAPTURE) {
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if (state->nonblock)
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closure->process_frames = r_process_frames_nonblocking;
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else
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closure->process_frames = r_process_frames_blocking;
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} else {
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if (state->nonblock)
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closure->process_frames = w_process_frames_nonblocking;
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else
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closure->process_frames = w_process_frames_blocking;
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}
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return 0;
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}
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static int irq_rw_process_frames(struct libasound_state *state,
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unsigned int *frame_count,
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struct mapper_context *mapper,
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struct container_context *cntrs)
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{
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struct rw_closure *closure = state->private_data;
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snd_pcm_state_t status;
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// Need to recover the stream.
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status = snd_pcm_state(state->handle);
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if (status != SND_PCM_STATE_RUNNING && status != SND_PCM_STATE_PREPARED)
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return -EPIPE;
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// NOTE: Actually, status can be shift always.
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return closure->process_frames(state, status, frame_count, mapper, cntrs);
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}
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static void irq_rw_post_process(struct libasound_state *state)
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{
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struct rw_closure *closure = state->private_data;
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frame_cache_destroy(&closure->cache);
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}
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const struct xfer_libasound_ops xfer_libasound_irq_rw_ops = {
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.pre_process = irq_rw_pre_process,
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.process_frames = irq_rw_process_frames,
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.post_process = irq_rw_post_process,
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.private_size = sizeof(struct rw_closure),
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};
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