In alsa-lib PCM API, snd_pcm_read[i|n]() and snd_pcm_write[i|n] can be used with non-blocking mode. This is available when SND_PCM_NONBLOCK is used as 'mode' argument for a call of snd_pcm_open().
This commit adds support this type of operation. To reduce CPU usage, this commit uses 'snd_pcm_wait()' to wait for event notification.
Below lines are examples to execute: $ axfer transfer -N -P -d 2 -D hw:0,3 /dev/urandom -f dat -vvv $ axfer transfer -N -C -d 2 -D hw:1,0 /dev/null -r 48000 -vvv
Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp --- axfer/xfer-libasound-irq-rw.c | 102 ++++++++++++++++++++++++++++++++-- axfer/xfer-libasound.c | 16 +++++- axfer/xfer-libasound.h | 1 + 3 files changed, 113 insertions(+), 6 deletions(-)
diff --git a/axfer/xfer-libasound-irq-rw.c b/axfer/xfer-libasound-irq-rw.c index 59634b4..f05ac4b 100644 --- a/axfer/xfer-libasound-irq-rw.c +++ b/axfer/xfer-libasound-irq-rw.c @@ -117,6 +117,51 @@ error: return err; }
+static int r_process_frames_nonblocking(struct libasound_state *state, + snd_pcm_state_t status, + unsigned int *frame_count, + struct mapper_context *mapper, + struct container_context *cntrs) +{ + snd_pcm_sframes_t avail; + snd_pcm_uframes_t avail_count; + int err = 0; + + if (status != SND_PCM_STATE_RUNNING) { + err = snd_pcm_start(state->handle); + if (err < 0) + goto error; + } + + // Wait for hardware IRQ when no available space. + err = snd_pcm_wait(state->handle, -1); + if (err < 0) + goto error; + + // Check available space on the buffer. + avail = snd_pcm_avail(state->handle); + if (avail < 0) { + err = avail; + goto error; + } + avail_count = (snd_pcm_uframes_t)avail; + + if (avail_count == 0) { + // Let's go to a next iteration. + err = 0; + goto error; + } + + err = read_frames(state, frame_count, avail_count, mapper, cntrs); + if (err < 0) + goto error; + + return 0; +error: + *frame_count = 0; + return err; +} + static int write_frames(struct libasound_state *state, unsigned int *frame_count, unsigned int avail_count, struct mapper_context *mapper, @@ -231,6 +276,48 @@ error: return err; }
+static int w_process_frames_nonblocking(struct libasound_state *state, + snd_pcm_state_t status, + unsigned int *frame_count, + struct mapper_context *mapper, + struct container_context *cntrs) +{ + snd_pcm_sframes_t avail; + unsigned int avail_count; + int err; + + // Wait for hardware IRQ when no left space. + err = snd_pcm_wait(state->handle, -1); + if (err < 0) + goto error; + + // Check available space on the buffer. + avail = snd_pcm_avail(state->handle); + if (avail < 0) { + err = avail; + goto error; + } + avail_count = (unsigned int)avail; + + if (avail_count == 0) { + // Let's go to a next iteration. + err = 0; + goto error; + } + + err = write_frames(state, frame_count, avail_count, mapper, cntrs); + if (err < 0) + goto error; + + // NOTE: The substream starts automatically when the accumulated number + // of queued data frame exceeds start_threshold. + + return 0; +error: + *frame_count = 0; + return err; +} + static int irq_rw_pre_process(struct libasound_state *state) { struct rw_closure *closure = state->private_data; @@ -267,10 +354,17 @@ static int irq_rw_pre_process(struct libasound_state *state) if (err < 0) return err;
- if (snd_pcm_stream(state->handle) == SND_PCM_STREAM_CAPTURE) - closure->process_frames = r_process_frames_blocking; - else - closure->process_frames = w_process_frames_blocking; + if (snd_pcm_stream(state->handle) == SND_PCM_STREAM_CAPTURE) { + if (state->nonblock) + closure->process_frames = r_process_frames_nonblocking; + else + closure->process_frames = r_process_frames_blocking; + } else { + if (state->nonblock) + closure->process_frames = w_process_frames_nonblocking; + else + closure->process_frames = w_process_frames_blocking; + }
return 0; } diff --git a/axfer/xfer-libasound.c b/axfer/xfer-libasound.c index 77c142e..cb26b69 100644 --- a/axfer/xfer-libasound.c +++ b/axfer/xfer-libasound.c @@ -14,9 +14,10 @@ enum no_short_opts { OPT_FATAL_ERRORS = 200, };
-#define S_OPTS "D:" +#define S_OPTS "D:N" static const struct option l_opts[] = { {"device", 1, 0, 'D'}, + {"nonblock", 0, 0, 'N'}, // For debugging. {"fatal-errors", 0, 0, OPT_FATAL_ERRORS}, }; @@ -46,6 +47,8 @@ static int xfer_libasound_parse_opt(struct xfer_context *xfer, int key,
if (key == 'D') state->node_literal = arg_duplicate_string(optarg, &err); + else if (key == 'N') + state->nonblock = true; else if (key == OPT_FATAL_ERRORS) state->finish_at_xrun = true; else @@ -91,10 +94,14 @@ static int set_access_hw_param(struct libasound_state *state) static int open_handle(struct xfer_context *xfer) { struct libasound_state *state = xfer->private_data; + int mode = 0; int err;
+ if (state->nonblock) + mode |= SND_PCM_NONBLOCK; + err = snd_pcm_open(&state->handle, state->node_literal, xfer->direction, - 0); + mode); if (err < 0) { logging(state, "Fail to open libasound PCM node for %s: %s\n", snd_pcm_stream_name(xfer->direction), @@ -378,7 +385,12 @@ static void xfer_libasound_post_process(struct xfer_context *xfer) logging(state, "snd_pcm_drop(): %s\n", snd_strerror(err)); } else { + // TODO: this is a bug in kernel land. + if (state->nonblock) + snd_pcm_nonblock(state->handle, 0); err = snd_pcm_drain(state->handle); + if (state->nonblock) + snd_pcm_nonblock(state->handle, 1); if (err < 0) logging(state, "snd_pcm_drain(): %s\n", snd_strerror(err)); diff --git a/axfer/xfer-libasound.h b/axfer/xfer-libasound.h index 270288d..6656aeb 100644 --- a/axfer/xfer-libasound.h +++ b/axfer/xfer-libasound.h @@ -31,6 +31,7 @@ struct libasound_state { char *node_literal;
bool finish_at_xrun:1; + bool nonblock:1; };
// For internal use in 'libasound' module.