ALSA: core: selection of audio_tstamp type and accuracy reports
Audio timestamps can be extracted from sample counters, wall clocks,
PHC clocks (Ethernet AVB), on-demand synchronized snapshots. This
patch provides the ability to report timestamping capabilities, select
timestamp types and retrieve timestamp accuracy, if supported.
Details can be found in Documentations/sound/alsa/timestamping.txt
This functionality is introduced by reclaiming the reserved_aligned
field introduced by commit9c7066aef4a5eb8e4063de28f06c508bf6f2963a
in snd_pcm_status to provide userspace with selection/query capabilities.
Additional driver_tstamp and audio_tstamp_accuracy fields are also added.
snd_pcm_mmap_status remains a read-only structure with only
the audio timestamp value accessible from user space. The selection
of audio timestamp type is done through snd_pcm_status only
This commit does not impact ABI and does not impact the default
behavior. By default audio timestamp is aligned with hw_pointer and
reports the DMA position. Backwards compatibility is handled by using
the HDAudio wall clock for playback and the hw_ptr for all other
cases.
For timestamp selection a new STATUS_EXT ioctl is introduced with
read/write parameters. Alsa-lib will be modified to make use of
STATUS_EXT.
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index c0ddb7e..60f0e48 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -60,6 +60,9 @@
struct snd_pcm_substream;
+struct snd_pcm_audio_tstamp_config; /* definitions further down */
+struct snd_pcm_audio_tstamp_report;
+
struct snd_pcm_ops {
int (*open)(struct snd_pcm_substream *substream);
int (*close)(struct snd_pcm_substream *substream);
@@ -281,6 +284,58 @@
struct snd_pcm_hwptr_log;
+/*
+ * userspace-provided audio timestamp config to kernel,
+ * structure is for internal use only and filled with dedicated unpack routine
+ */
+struct snd_pcm_audio_tstamp_config {
+ /* 5 of max 16 bits used */
+ u32 type_requested:4;
+ u32 report_delay:1; /* add total delay to A/D or D/A */
+};
+
+static inline void snd_pcm_unpack_audio_tstamp_config(__u32 data,
+ struct snd_pcm_audio_tstamp_config *config)
+{
+ config->type_requested = data & 0xF;
+ config->report_delay = (data >> 4) & 1;
+}
+
+/*
+ * kernel-provided audio timestamp report to user-space
+ * structure is for internal use only and read by dedicated pack routine
+ */
+struct snd_pcm_audio_tstamp_report {
+ /* 6 of max 16 bits used for bit-fields */
+
+ /* for backwards compatibility */
+ u32 valid:1;
+
+ /* actual type if hardware could not support requested timestamp */
+ u32 actual_type:4;
+
+ /* accuracy represented in ns units */
+ u32 accuracy_report:1; /* 0 if accuracy unknown, 1 if accuracy field is valid */
+ u32 accuracy; /* up to 4.29s, will be packed in separate field */
+};
+
+static inline void snd_pcm_pack_audio_tstamp_report(__u32 *data, __u32 *accuracy,
+ const struct snd_pcm_audio_tstamp_report *report)
+{
+ u32 tmp;
+
+ tmp = report->accuracy_report;
+ tmp <<= 4;
+ tmp |= report->actual_type;
+ tmp <<= 1;
+ tmp |= report->valid;
+
+ *data &= 0xffff; /* zero-clear MSBs */
+ *data |= (tmp << 16);
+ *accuracy = report->accuracy;
+}
+
+
struct snd_pcm_runtime {
/* -- Status -- */
struct snd_pcm_substream *trigger_master;
@@ -361,6 +416,11 @@
struct snd_dma_buffer *dma_buffer_p; /* allocated buffer */
+ /* -- audio timestamp config -- */
+ struct snd_pcm_audio_tstamp_config audio_tstamp_config;
+ struct snd_pcm_audio_tstamp_report audio_tstamp_report;
+ struct timespec driver_tstamp;
+
#if defined(CONFIG_SND_PCM_OSS) || defined(CONFIG_SND_PCM_OSS_MODULE)
/* -- OSS things -- */
struct snd_pcm_oss_runtime oss;