@@ -330,6 +330,17 @@ typedef enum _snd_pcm_tstamp_type {
SND_PCM_TSTAMP_TYPE_LAST = SND_PCM_TSTAMP_TYPE_MONOTONIC_RAW,
} snd_pcm_tstamp_type_t;
+/** PCM start_at clock types */
+typedef enum _snd_pcm_startat_clock_type {
+ /** POSIX CLOCK_REALTIME equivalent */
+ SND_PCM_STARTAT_CLOCK_TYPE_GETTIMEOFDAY = 0,
+ /** POSIX CLOCK_MONOTONIC equivalent */
+ SND_PCM_STARTAT_CLOCK_TYPE_MONOTONIC,
+ /** Default link clock */
+ SND_PCM_STARTAT_CLOCK_TYPE_LINK,
+ SND_PCM_STARTAT_CLOCK_TYPE_LAST = SND_PCM_STARTAT_CLOCK_TYPE_LINK,
+} snd_pcm_startat_clock_type_t;
+
/** Unsigned frames quantity */
typedef unsigned long snd_pcm_uframes_t;
/** Signed frames quantity */
@@ -478,6 +489,9 @@ 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, snd_pcm_startat_clock_type_t clock_type, const snd_htimestamp_t* start_time);
+int snd_pcm_start_at_abort(snd_pcm_t *pcm);
+int snd_pcm_start_at_gettime(snd_pcm_t *pcm, snd_pcm_startat_clock_type_t clock_type, snd_htimestamp_t* current_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);
@@ -984,6 +998,7 @@ snd_pcm_sframes_t snd_pcm_status_get_delay(const snd_pcm_status_t *obj);
snd_pcm_uframes_t snd_pcm_status_get_avail(const snd_pcm_status_t *obj);
snd_pcm_uframes_t snd_pcm_status_get_avail_max(const snd_pcm_status_t *obj);
snd_pcm_uframes_t snd_pcm_status_get_overrange(const snd_pcm_status_t *obj);
+void snd_pcm_status_get_startat_state(const snd_pcm_status_t *obj, int *pending, snd_pcm_startat_clock_type_t *clock_type, snd_htimestamp_t *start_time);
/** \} */
@@ -1085,6 +1085,74 @@ int snd_pcm_start(snd_pcm_t *pcm)
}
/**
+ * \brief Start a PCM at a specified point in the future
+ * \param pcm PCM handle
+ * \param clock_type Specifies the start_at clock with which to interpret \p start_time
+ * \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, tstamp_class or tstamp_type is 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.
+ *
+ * Any pending timer is unconditionally cancelled.
+ */
+int snd_pcm_start_at(snd_pcm_t *pcm, snd_pcm_startat_clock_type_t clock_type, 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, clock_type, start_time);
+ }
+ return -EINVAL;
+}
+
+/**
+ * \brief Abort the pending PCM start_at timer
+ * \param pcm PCM handle
+ * \return 0 on success otherwise a negative error code
+ *
+ * If a start_at timer is pending, it is cancelled.
+ */
+int snd_pcm_start_at_abort(snd_pcm_t *pcm)
+{
+ assert(pcm);
+ if (CHECK_SANITY(! pcm->setup)) {
+ SNDMSG("PCM not set up");
+ return -EIO;
+ }
+ if (pcm->fast_ops->start_at_abort) {
+ return pcm->fast_ops->start_at_abort(pcm->fast_op_arg);
+ }
+ return -EINVAL;
+}
+
+/**
+ * \brief Get current time for a given start_at clock
+ * \param pcm PCM handle
+ * \param clock_type Start_at clock type e.g. SND_PCM_STARTAT_CLOCK_TYPE_GETTIMEOFDAY
+ * \return 0 on success otherwise a negative error code
+ */
+int snd_pcm_start_at_gettime(snd_pcm_t *pcm, snd_pcm_startat_clock_type_t clock_type, snd_htimestamp_t *current_time)
+{
+ assert(pcm);
+ if (CHECK_SANITY(! pcm->setup)) {
+ SNDMSG("PCM not set up");
+ return -EIO;
+ }
+ if (pcm->fast_ops->start_at_gettime) {
+ return pcm->fast_ops->start_at_gettime(pcm->fast_op_arg, clock_type, current_time);
+ }
+ return -EINVAL;
+}
+
+/**
* \brief Stop a PCM dropping pending frames
* \param pcm PCM handle
* \return 0 on success otherwise a negative error code
@@ -6380,6 +6448,20 @@ snd_pcm_uframes_t snd_pcm_status_get_overrange(const snd_pcm_status_t *obj)
}
/**
+ * \brief Get status of a pending start_at timer, if any.
+ * \param pending output param: 1 if start_at timer pending, 0 otherwise
+ * \param clock_type output param: if pending == 1, is updated with current start_at timer clock_type
+ * \param start_time output param: if pending == 1, is updated with current start_at timer start_time
+ */
+void snd_pcm_status_get_startat_state(const snd_pcm_status_t *obj, int *pending, snd_pcm_startat_clock_type_t *clock_type, snd_htimestamp_t *start_time)
+{
+ assert(obj);
+ *pending = obj->start_at_pending;
+ *clock_type = obj->start_at_clock_type;
+ *start_time = obj->start_at_start_time;
+}
+
+/**
* \brief get size of #snd_pcm_info_t
* \return size in bytes
*/
Upcoming audio hardware has the ability to begin playback when the value of a high-precision free-running counter matches some programmable value. This patch exposes such capability in a general way, allowing for several clock sources, including both system clocks and audio hardware clocks. We define 3 new methods that operate on a snd_pcm_t, and 1 that operates on a snd_pcm_status_t. - snd_pcm_start_at() allows client code to delegate the starting of the stream to the kernel. - snd_pcm_start_at_abort() allows client code to cancel a previous call to snd_pcm_start_at(). - snd_pcm_start_at_gettime() allows client code to query the current time for a given clock. - snd_pcm_status_get_startat_state() allows client code to extract information about any pending start_at timer from a snd_pcm_status_t object. We define a new enum: snd_pcm_startat_clock_type_t, which reinforces a clean boundary between the capabilities of the timestamping system and the start_at system. The clock and audio hw sources are grouped together because the difference is irrelevant to the use of snd_pcm_start_at(). Signed-off-by: Tim Cussins <timcussins@eml.cc>