| Message ID | 20240506151218.377580-2-perex@perex.cz (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | ALSA: pcm: reinvent the stream synchronization ID API | expand |
On Mon, May 06, 2024 at 05:11:49PM +0200, Jaroslav Kysela wrote: > Until the commit e11f0f90a626 ("ALSA: pcm: remove SNDRV_PCM_IOCTL1_INFO > internal command"), there was a possibility to pass information > about the synchronized streams to the user space. The mentioned > commit removed blindly the appropriate code with an irrelevant comment. > > The revert may be appropriate, but since this API was lost for several > years without any complains, it's time to improve it. The hardware > parameters may change the used stream clock source (e.g. USB hardware) > so move this synchronization ID to hw_params as read-only field. > > It seems that pipewire can benefit from this API (disable adaptive > resampling for perfectly synchronized PCM streams) now. > > Cc: Takashi Sakamoto <takaswie@kernel.org> > Signed-off-by: Jaroslav Kysela <perex@perex.cz> > --- > include/sound/pcm.h | 11 ++++++++++- > include/uapi/sound/asound.h | 13 ++++--------- > sound/core/pcm_lib.c | 18 ++++++++++++++---- > sound/core/pcm_native.c | 6 ++++++ > sound/pci/emu10k1/p16v.c | 7 +++---- > 5 files changed, 37 insertions(+), 18 deletions(-) > > diff --git a/include/sound/pcm.h b/include/sound/pcm.h > index 210096f124ee..dae41b100517 100644 > --- a/include/sound/pcm.h > +++ b/include/sound/pcm.h > @@ -93,6 +93,7 @@ struct snd_pcm_ops { > #define SNDRV_PCM_IOCTL1_CHANNEL_INFO 2 > /* 3 is absent slot. */ > #define SNDRV_PCM_IOCTL1_FIFO_SIZE 4 > +#define SNDRV_PCM_IOCTL1_SYNC_ID 5 > > #define SNDRV_PCM_TRIGGER_STOP 0 > #define SNDRV_PCM_TRIGGER_START 1 > @@ -396,7 +397,7 @@ struct snd_pcm_runtime { > snd_pcm_uframes_t silence_start; /* starting pointer to silence area */ > snd_pcm_uframes_t silence_filled; /* already filled part of silence area */ > > - union snd_pcm_sync_id sync; /* hardware synchronization ID */ > + unsigned char sync[16]; /* hardware synchronization ID */ > > /* -- mmap -- */ > struct snd_pcm_mmap_status *status; > @@ -1565,6 +1566,14 @@ static inline u64 pcm_format_to_bits(snd_pcm_format_t pcm_format) > (__force int)(f) <= (__force int)SNDRV_PCM_FORMAT_LAST; \ > (f) = (__force snd_pcm_format_t)((__force int)(f) + 1)) > > +/** > + * is sync id (clock id) empty? > + */ > +static inline bool pcm_sync_empty(const unsigned char *sync) > +{ > + return strnlen((const char *)sync, 16) == 0; > +} > + For the sound card indexed by 0, it is problematic, since in the later change, the first element of array has 0. > /* printk helpers */ > #define pcm_err(pcm, fmt, args...) \ > dev_err((pcm)->card->dev, fmt, ##args) > diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h > index 628d46a0da92..c458172b32d5 100644 > --- a/include/uapi/sound/asound.h > +++ b/include/uapi/sound/asound.h > @@ -142,7 +142,7 @@ struct snd_hwdep_dsp_image { > * * > *****************************************************************************/ > > -#define SNDRV_PCM_VERSION SNDRV_PROTOCOL_VERSION(2, 0, 17) > +#define SNDRV_PCM_VERSION SNDRV_PROTOCOL_VERSION(2, 0, 18) > > typedef unsigned long snd_pcm_uframes_t; > typedef signed long snd_pcm_sframes_t; > @@ -330,12 +330,6 @@ enum { > #endif > }; > > -union snd_pcm_sync_id { > - unsigned char id[16]; > - unsigned short id16[8]; > - unsigned int id32[4]; > -}; > - > struct snd_pcm_info { > unsigned int device; /* RO/WR (control): device number */ > unsigned int subdevice; /* RO/WR (control): subdevice number */ > @@ -348,7 +342,7 @@ struct snd_pcm_info { > int dev_subclass; /* SNDRV_PCM_SUBCLASS_* */ > unsigned int subdevices_count; > unsigned int subdevices_avail; > - union snd_pcm_sync_id sync; /* hardware synchronization ID */ > + unsigned char pad1[16]; /* was: hardware synchronization ID */ > unsigned char reserved[64]; /* reserved for future... */ > }; > > @@ -420,7 +414,8 @@ struct snd_pcm_hw_params { > unsigned int rate_num; /* R: rate numerator */ > unsigned int rate_den; /* R: rate denominator */ > snd_pcm_uframes_t fifo_size; /* R: chip FIFO size in frames */ > - unsigned char reserved[64]; /* reserved for future */ > + unsigned char sync[16]; /* R: synchronization ID (perfect sync - one clock source) */ > + unsigned char reserved[48]; /* reserved for future */ > }; > > enum { As long as I checked, the above change are safe for backward-compatibility and compat ioctl. They keep the same size of structure and the same offset of member in each of i386/ILP32/LP64 data models, > diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c > index 6f73b3c2c205..84b948db3393 100644 > --- a/sound/core/pcm_lib.c > +++ b/sound/core/pcm_lib.c > @@ -525,10 +525,8 @@ void snd_pcm_set_sync(struct snd_pcm_substream *substream) > { > struct snd_pcm_runtime *runtime = substream->runtime; > > - runtime->sync.id32[0] = substream->pcm->card->number; > - runtime->sync.id32[1] = -1; > - runtime->sync.id32[2] = -1; > - runtime->sync.id32[3] = -1; > + *(__u32 *)runtime->sync = cpu_to_le32(substream->pcm->card->number); > + memset(runtime->sync + 4, 0xff, sizeof(runtime->sync) - 4); > } > EXPORT_SYMBOL(snd_pcm_set_sync); I mentioned about the issue in the above. > @@ -1810,6 +1808,16 @@ static int snd_pcm_lib_ioctl_fifo_size(struct snd_pcm_substream *substream, > return 0; > } > > +static int snd_pcm_lib_ioctl_sync_id(struct snd_pcm_substream *substream, > + void *arg) > +{ > + struct snd_pcm_hw_params *params = arg; > + > + if (pcm_sync_empty(params->sync)) > + memcpy(params->sync, &substream->runtime->sync, sizeof(params->sync)); > + return 0; > +} > + I mentioned about the issue in the above. > /** > * snd_pcm_lib_ioctl - a generic PCM ioctl callback > * @substream: the pcm substream instance > @@ -1831,6 +1839,8 @@ int snd_pcm_lib_ioctl(struct snd_pcm_substream *substream, > return snd_pcm_lib_ioctl_channel_info(substream, arg); > case SNDRV_PCM_IOCTL1_FIFO_SIZE: > return snd_pcm_lib_ioctl_fifo_size(substream, arg); > + case SNDRV_PCM_IOCTL1_SYNC_ID: > + return snd_pcm_lib_ioctl_sync_id(substream, arg); > } > return -ENXIO; > } > diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c > index 0b76e76823d2..63fcb08ee93d 100644 > --- a/sound/core/pcm_native.c > +++ b/sound/core/pcm_native.c > @@ -533,6 +533,12 @@ static int fixup_unreferenced_params(struct snd_pcm_substream *substream, > SNDRV_PCM_INFO_MMAP_VALID); > } > > + err = snd_pcm_ops_ioctl(substream, > + SNDRV_PCM_IOCTL1_SYNC_ID, > + params); > + if (err < 0) > + return err; > + > return 0; > } > > diff --git a/sound/pci/emu10k1/p16v.c b/sound/pci/emu10k1/p16v.c > index e7f097cae574..773725dbdfbd 100644 > --- a/sound/pci/emu10k1/p16v.c > +++ b/sound/pci/emu10k1/p16v.c > @@ -174,10 +174,9 @@ static int snd_p16v_pcm_open_playback_channel(struct snd_pcm_substream *substrea > if (err < 0) > return err; > > - runtime->sync.id32[0] = substream->pcm->card->number; > - runtime->sync.id32[1] = 'P'; > - runtime->sync.id32[2] = 16; > - runtime->sync.id32[3] = 'V'; > + *(__u32 *)runtime->sync = cpu_to_le32(substream->pcm->card->number); > + memset(runtime->sync + 4, 0, sizeof(runtime->sync) - 4); > + strncpy(runtime->sync + 4, "P16V", 4); The serialization would not keep the same data before the change, since the third, fourth, and fifth elements are 0x31, 0x36, and 0x56, instead of 0x10, 0x56, and 0x00. > return 0; > } > -- > 2.43.0 >
On 07. 05. 24 5:04, Takashi Sakamoto wrote: >> +/** >> + * is sync id (clock id) empty? >> + */ >> +static inline bool pcm_sync_empty(const unsigned char *sync) >> +{ >> + return strnlen((const char *)sync, 16) == 0; >> +} >> + > > For the sound card indexed by 0, it is problematic, since in the later > change, the first element of array has 0. Oops. It was a thinko. I replaced this with a full zero comparison in v3 of this patch. ... >> @@ -420,7 +414,8 @@ struct snd_pcm_hw_params { >> unsigned int rate_num; /* R: rate numerator */ >> unsigned int rate_den; /* R: rate denominator */ >> snd_pcm_uframes_t fifo_size; /* R: chip FIFO size in frames */ >> - unsigned char reserved[64]; /* reserved for future */ >> + unsigned char sync[16]; /* R: synchronization ID (perfect sync - one clock source) */ >> + unsigned char reserved[48]; /* reserved for future */ >> }; >> >> enum { > > As long as I checked, the above change are safe for > backward-compatibility and compat ioctl. They keep the same size of > structure and the same offset of member in each of i386/ILP32/LP64 data > models, Thank you for this verification and review. >> + *(__u32 *)runtime->sync = cpu_to_le32(substream->pcm->card->number); >> + memset(runtime->sync + 4, 0, sizeof(runtime->sync) - 4); >> + strncpy(runtime->sync + 4, "P16V", 4); > > The serialization would not keep the same data before the change, since > the third, fourth, and fifth elements are 0x31, 0x36, and 0x56, instead > of 0x10, 0x56, and 0x00. It does not matter. See the extended comment for snd_pcm_set_sync_per_card in v3. The ID should be used only for a comparison among PCM devices without any interpretation. Thank you, Jaroslav
diff --git a/include/sound/pcm.h b/include/sound/pcm.h index 210096f124ee..dae41b100517 100644 --- a/include/sound/pcm.h +++ b/include/sound/pcm.h @@ -93,6 +93,7 @@ struct snd_pcm_ops { #define SNDRV_PCM_IOCTL1_CHANNEL_INFO 2 /* 3 is absent slot. */ #define SNDRV_PCM_IOCTL1_FIFO_SIZE 4 +#define SNDRV_PCM_IOCTL1_SYNC_ID 5 #define SNDRV_PCM_TRIGGER_STOP 0 #define SNDRV_PCM_TRIGGER_START 1 @@ -396,7 +397,7 @@ struct snd_pcm_runtime { snd_pcm_uframes_t silence_start; /* starting pointer to silence area */ snd_pcm_uframes_t silence_filled; /* already filled part of silence area */ - union snd_pcm_sync_id sync; /* hardware synchronization ID */ + unsigned char sync[16]; /* hardware synchronization ID */ /* -- mmap -- */ struct snd_pcm_mmap_status *status; @@ -1565,6 +1566,14 @@ static inline u64 pcm_format_to_bits(snd_pcm_format_t pcm_format) (__force int)(f) <= (__force int)SNDRV_PCM_FORMAT_LAST; \ (f) = (__force snd_pcm_format_t)((__force int)(f) + 1)) +/** + * is sync id (clock id) empty? + */ +static inline bool pcm_sync_empty(const unsigned char *sync) +{ + return strnlen((const char *)sync, 16) == 0; +} + /* printk helpers */ #define pcm_err(pcm, fmt, args...) \ dev_err((pcm)->card->dev, fmt, ##args) diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h index 628d46a0da92..c458172b32d5 100644 --- a/include/uapi/sound/asound.h +++ b/include/uapi/sound/asound.h @@ -142,7 +142,7 @@ struct snd_hwdep_dsp_image { * * *****************************************************************************/ -#define SNDRV_PCM_VERSION SNDRV_PROTOCOL_VERSION(2, 0, 17) +#define SNDRV_PCM_VERSION SNDRV_PROTOCOL_VERSION(2, 0, 18) typedef unsigned long snd_pcm_uframes_t; typedef signed long snd_pcm_sframes_t; @@ -330,12 +330,6 @@ enum { #endif }; -union snd_pcm_sync_id { - unsigned char id[16]; - unsigned short id16[8]; - unsigned int id32[4]; -}; - struct snd_pcm_info { unsigned int device; /* RO/WR (control): device number */ unsigned int subdevice; /* RO/WR (control): subdevice number */ @@ -348,7 +342,7 @@ struct snd_pcm_info { int dev_subclass; /* SNDRV_PCM_SUBCLASS_* */ unsigned int subdevices_count; unsigned int subdevices_avail; - union snd_pcm_sync_id sync; /* hardware synchronization ID */ + unsigned char pad1[16]; /* was: hardware synchronization ID */ unsigned char reserved[64]; /* reserved for future... */ }; @@ -420,7 +414,8 @@ struct snd_pcm_hw_params { unsigned int rate_num; /* R: rate numerator */ unsigned int rate_den; /* R: rate denominator */ snd_pcm_uframes_t fifo_size; /* R: chip FIFO size in frames */ - unsigned char reserved[64]; /* reserved for future */ + unsigned char sync[16]; /* R: synchronization ID (perfect sync - one clock source) */ + unsigned char reserved[48]; /* reserved for future */ }; enum { diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c index 6f73b3c2c205..84b948db3393 100644 --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -525,10 +525,8 @@ void snd_pcm_set_sync(struct snd_pcm_substream *substream) { struct snd_pcm_runtime *runtime = substream->runtime; - runtime->sync.id32[0] = substream->pcm->card->number; - runtime->sync.id32[1] = -1; - runtime->sync.id32[2] = -1; - runtime->sync.id32[3] = -1; + *(__u32 *)runtime->sync = cpu_to_le32(substream->pcm->card->number); + memset(runtime->sync + 4, 0xff, sizeof(runtime->sync) - 4); } EXPORT_SYMBOL(snd_pcm_set_sync); @@ -1810,6 +1808,16 @@ static int snd_pcm_lib_ioctl_fifo_size(struct snd_pcm_substream *substream, return 0; } +static int snd_pcm_lib_ioctl_sync_id(struct snd_pcm_substream *substream, + void *arg) +{ + struct snd_pcm_hw_params *params = arg; + + if (pcm_sync_empty(params->sync)) + memcpy(params->sync, &substream->runtime->sync, sizeof(params->sync)); + return 0; +} + /** * snd_pcm_lib_ioctl - a generic PCM ioctl callback * @substream: the pcm substream instance @@ -1831,6 +1839,8 @@ int snd_pcm_lib_ioctl(struct snd_pcm_substream *substream, return snd_pcm_lib_ioctl_channel_info(substream, arg); case SNDRV_PCM_IOCTL1_FIFO_SIZE: return snd_pcm_lib_ioctl_fifo_size(substream, arg); + case SNDRV_PCM_IOCTL1_SYNC_ID: + return snd_pcm_lib_ioctl_sync_id(substream, arg); } return -ENXIO; } diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 0b76e76823d2..63fcb08ee93d 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -533,6 +533,12 @@ static int fixup_unreferenced_params(struct snd_pcm_substream *substream, SNDRV_PCM_INFO_MMAP_VALID); } + err = snd_pcm_ops_ioctl(substream, + SNDRV_PCM_IOCTL1_SYNC_ID, + params); + if (err < 0) + return err; + return 0; } diff --git a/sound/pci/emu10k1/p16v.c b/sound/pci/emu10k1/p16v.c index e7f097cae574..773725dbdfbd 100644 --- a/sound/pci/emu10k1/p16v.c +++ b/sound/pci/emu10k1/p16v.c @@ -174,10 +174,9 @@ static int snd_p16v_pcm_open_playback_channel(struct snd_pcm_substream *substrea if (err < 0) return err; - runtime->sync.id32[0] = substream->pcm->card->number; - runtime->sync.id32[1] = 'P'; - runtime->sync.id32[2] = 16; - runtime->sync.id32[3] = 'V'; + *(__u32 *)runtime->sync = cpu_to_le32(substream->pcm->card->number); + memset(runtime->sync + 4, 0, sizeof(runtime->sync) - 4); + strncpy(runtime->sync + 4, "P16V", 4); return 0; }
Until the commit e11f0f90a626 ("ALSA: pcm: remove SNDRV_PCM_IOCTL1_INFO internal command"), there was a possibility to pass information about the synchronized streams to the user space. The mentioned commit removed blindly the appropriate code with an irrelevant comment. The revert may be appropriate, but since this API was lost for several years without any complains, it's time to improve it. The hardware parameters may change the used stream clock source (e.g. USB hardware) so move this synchronization ID to hw_params as read-only field. It seems that pipewire can benefit from this API (disable adaptive resampling for perfectly synchronized PCM streams) now. Cc: Takashi Sakamoto <takaswie@kernel.org> Signed-off-by: Jaroslav Kysela <perex@perex.cz> --- include/sound/pcm.h | 11 ++++++++++- include/uapi/sound/asound.h | 13 ++++--------- sound/core/pcm_lib.c | 18 ++++++++++++++---- sound/core/pcm_native.c | 6 ++++++ sound/pci/emu10k1/p16v.c | 7 +++---- 5 files changed, 37 insertions(+), 18 deletions(-)