[alsa-devel] [RFC] alsa-lib: Add snd_pcm_start_at
Tim Cussins
timcussins at eml.cc
Wed Dec 3 17:27:29 CET 2014
snd_pcm_start_at() - alsa-lib
The headlines:
- Provide userspace snd_pcm_start_at, leverage new ioctl
- Provide some decent doxygen guff
diff --git a/include/pcm.h b/include/pcm.h
index 0655e7f..bbe6e79 100644
--- a/include/pcm.h
+++ b/include/pcm.h
@@ -325,9 +325,10 @@ typedef enum _snd_pcm_tstamp {
typedef enum _snd_pcm_tstamp_type {
SND_PCM_TSTAMP_TYPE_GETTIMEOFDAY = 0, /** gettimeofday equivalent */
- SND_PCM_TSTAMP_TYPE_MONOTONIC, /** posix_clock_monotonic equivalent */
+ SND_PCM_TSTAMP_TYPE_MONOTONIC, /** posix_clock_monotonic equivalent */
SND_PCM_TSTAMP_TYPE_MONOTONIC_RAW, /** monotonic_raw (no NTP) */
- SND_PCM_TSTAMP_TYPE_LAST = SND_PCM_TSTAMP_TYPE_MONOTONIC_RAW,
+ SND_PCM_TSTAMP_TYPE_AUDIO_WALLCLOCK, /** audio hw clock */
+ SND_PCM_TSTAMP_TYPE_LAST = SND_PCM_TSTAMP_TYPE_AUDIO_WALLCLOCK,
} snd_pcm_tstamp_type_t;
/** Unsigned frames quantity */
@@ -478,6 +479,7 @@ int snd_pcm_prepare(snd_pcm_t *pcm);
int snd_pcm_reset(snd_pcm_t *pcm);
int snd_pcm_status(snd_pcm_t *pcm, snd_pcm_status_t *status);
int snd_pcm_start(snd_pcm_t *pcm);
+int snd_pcm_start_at(snd_pcm_t *pcm, const snd_htimestamp_t* start_time);
int snd_pcm_drop(snd_pcm_t *pcm);
int snd_pcm_drain(snd_pcm_t *pcm);
int snd_pcm_pause(snd_pcm_t *pcm, int enable);
diff --git a/include/sound/asound.h b/include/sound/asound.h
index 941d32f..bcc49dc 100644
--- a/include/sound/asound.h
+++ b/include/sound/asound.h
@@ -467,8 +467,9 @@ struct snd_xfern {
enum {
SNDRV_PCM_TSTAMP_TYPE_GETTIMEOFDAY = 0, /* gettimeofday equivalent */
SNDRV_PCM_TSTAMP_TYPE_MONOTONIC, /* posix_clock_monotonic equivalent */
- SNDRV_PCM_TSTAMP_TYPE_MONOTONIC_RAW, /* monotonic_raw (no NTP) */
- SNDRV_PCM_TSTAMP_TYPE_LAST = SNDRV_PCM_TSTAMP_TYPE_MONOTONIC_RAW,
+ SNDRV_PCM_TSTAMP_TYPE_MONOTONIC_RAW, /* monotonic_raw (no NTP) */
+ SNDRV_PCM_TSTAMP_TYPE_AUDIO_WALLCLOCK, /* audio hw clock */
+ SNDRV_PCM_TSTAMP_TYPE_LAST = SNDRV_PCM_TSTAMP_TYPE_AUDIO_WALLCLOCK,
};
/* channel positions */
@@ -549,6 +550,8 @@ enum {
#define SNDRV_PCM_IOCTL_READN_FRAMES _IOR('A', 0x53, struct snd_xfern)
#define SNDRV_PCM_IOCTL_LINK _IOW('A', 0x60, int)
#define SNDRV_PCM_IOCTL_UNLINK _IO('A', 0x61)
+#define SNDRV_PCM_IOCTL_START_AT _IOW('A', 0x62, snd_htimestamp_t)
+
/*****************************************************************************
* *
diff --git a/src/pcm/pcm.c b/src/pcm/pcm.c
index baa47c7..61158cb 100644
--- a/src/pcm/pcm.c
+++ b/src/pcm/pcm.c
@@ -1085,6 +1085,38 @@ int snd_pcm_start(snd_pcm_t *pcm)
}
/**
+ * \brief Start a PCM at a specified point in the future
+ * \param pcm PCM handle
+ * \param start_time Absolute time at which to start the stream
+ * \return 0 on success otherwise a negative error code
+ * \retval -ENOSYS operation not supported for the current timestamp type
+ * \retval -EINVAL timespec invalid
+ * \retval -ETIME requested start_time cannot be satisfied
+ *
+ * This method is non-blocking: It establishes an appropriate timer in the kernel
+ * that will start the stream on expiry.
+ *
+ * The timer is unconditionally cancelled upon any \a attempt to change the stream
+ * state e.g. drop, drain, start, start_at.
+ *
+ * \p start_time is interpreted in the context of the stream snd_pcm_tstamp_type,
+ * set using \link ::snd_pcm_sw_params_set_tstamp_type() \endlink.
+ */
+int snd_pcm_start_at(snd_pcm_t *pcm, const snd_htimestamp_t *start_time)
+{
+ assert(pcm);
+ assert(start_time);
+ if (CHECK_SANITY(! pcm->setup)) {
+ SNDMSG("PCM not set up");
+ return -EIO;
+ }
+ if (pcm->fast_ops->start_at) {
+ return pcm->fast_ops->start_at(pcm->fast_op_arg, start_time);
+ }
+ return -EINVAL;
+}
+
+/**
* \brief Stop a PCM dropping pending frames
* \param pcm PCM handle
* \return 0 on success otherwise a negative error code
@@ -1693,6 +1725,7 @@ static const char *const snd_pcm_tstamp_type_names[] = {
TSTAMP_TYPE(GETTIMEOFDAY),
TSTAMP_TYPE(MONOTONIC),
TSTAMP_TYPE(MONOTONIC_RAW),
+ TSTAMP_TYPE(AUDIO_WALLCLOCK),
};
#endif
diff --git a/src/pcm/pcm_hw.c b/src/pcm/pcm_hw.c
index c34b766..aa0c7ba 100644
--- a/src/pcm/pcm_hw.c
+++ b/src/pcm/pcm_hw.c
@@ -447,6 +447,11 @@ static int snd_pcm_hw_sw_params(snd_pcm_t *pcm, snd_pcm_sw_params_t * params)
hw->mmap_control->avail_min = params->avail_min;
return sync_ptr(hw, 0);
}
+ if (params->tstamp_type == SND_PCM_TSTAMP_TYPE_AUDIO_WALLCLOCK &&
+ hw->version < SNDRV_PROTOCOL_VERSION(2, 0, 12)) {
+ SYSMSG("Kernel doesn't support SND_PCM_TSTAMP_TYPE_AUDIO_WALLCLOCK");
+ return -EINVAL;
+ }
if (params->tstamp_type == SND_PCM_TSTAMP_TYPE_MONOTONIC_RAW &&
hw->version < SNDRV_PROTOCOL_VERSION(2, 0, 12)) {
SYSMSG("Kernel doesn't support SND_PCM_TSTAMP_TYPE_MONOTONIC_RAW");
@@ -620,6 +625,20 @@ static int snd_pcm_hw_start(snd_pcm_t *pcm)
return 0;
}
+static int snd_pcm_hw_start_at(snd_pcm_t *pcm, const snd_htimestamp_t *start_time)
+{
+ snd_pcm_hw_t *hw = pcm->private_data;
+ int err;
+
+ sync_ptr(hw, 0);
+ if (ioctl(hw->fd, SNDRV_PCM_IOCTL_START_AT, start_time) < 0) {
+ err = -errno;
+ SYSMSG("SNDRV_PCM_IOCTL_START_AT failed (%i)", err);
+ return err;
+ }
+ return 0;
+}
+
static int snd_pcm_hw_drop(snd_pcm_t *pcm)
{
snd_pcm_hw_t *hw = pcm->private_data;
@@ -1336,6 +1355,7 @@ static const snd_pcm_fast_ops_t snd_pcm_hw_fast_ops = {
.prepare = snd_pcm_hw_prepare,
.reset = snd_pcm_hw_reset,
.start = snd_pcm_hw_start,
+ .start_at = snd_pcm_hw_start_at,
.drop = snd_pcm_hw_drop,
.drain = snd_pcm_hw_drain,
.pause = snd_pcm_hw_pause,
diff --git a/src/pcm/pcm_local.h b/src/pcm/pcm_local.h
index 394505f..6829750 100644
--- a/src/pcm/pcm_local.h
+++ b/src/pcm/pcm_local.h
@@ -154,6 +154,7 @@ typedef struct {
int (*prepare)(snd_pcm_t *pcm);
int (*reset)(snd_pcm_t *pcm);
int (*start)(snd_pcm_t *pcm);
+ int (*start_at)(snd_pcm_t *pcm, const snd_htimestamp_t *start_time);
int (*drop)(snd_pcm_t *pcm);
int (*drain)(snd_pcm_t *pcm);
int (*pause)(snd_pcm_t *pcm, int enable);
--
1.7.10.4
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