On Wed, 22 Nov 2017 20:17:34 +0100, Maciej S. Szmigiero wrote:
This format is similar to existing SNDRV_PCM_FORMAT_{S,U}20_3 that keep 20-bit PCM samples in 3 bytes, however i.MX6 platform SSI FIFO does not allow 3-byte accesses (including DMA) so a 4-byte format is needed for it.
Signed-off-by: Maciej S. Szmigiero mail@maciej.szmigiero.name
include/sound/pcm.h | 8 ++++++++ include/sound/soc-dai.h | 2 ++ include/uapi/sound/asound.h | 10 +++++++++- sound/core/pcm_misc.c | 16 ++++++++++++++++ 4 files changed, 35 insertions(+), 1 deletion(-)
diff --git a/include/sound/pcm.h b/include/sound/pcm.h index 24febf9e177c..7ad2d3f0934f 100644 --- a/include/sound/pcm.h +++ b/include/sound/pcm.h @@ -191,6 +191,10 @@ struct snd_pcm_ops { #define SNDRV_PCM_FMTBIT_DSD_U32_LE _SNDRV_PCM_FMTBIT(DSD_U32_LE) #define SNDRV_PCM_FMTBIT_DSD_U16_BE _SNDRV_PCM_FMTBIT(DSD_U16_BE) #define SNDRV_PCM_FMTBIT_DSD_U32_BE _SNDRV_PCM_FMTBIT(DSD_U32_BE) +#define SNDRV_PCM_FMTBIT_S20_4LE _SNDRV_PCM_FMTBIT(S20_4LE) +#define SNDRV_PCM_FMTBIT_U20_4LE _SNDRV_PCM_FMTBIT(U20_4LE) +#define SNDRV_PCM_FMTBIT_S20_4BE _SNDRV_PCM_FMTBIT(S20_4BE) +#define SNDRV_PCM_FMTBIT_U20_4BE _SNDRV_PCM_FMTBIT(U20_4BE)
The conventional names aren't with "4" suffix, e.g. SNDRV_PCM_FMTBIT_S20_LE.
Also, there are still empty slots under 32, e.g. start from 25. The formats over 31 were used for 3 bytes or other unusual formats (although nowadays it makes little sense), and the slots < 32 would fit for 4 bytes linear format.
It's still an open question whether we should increase the protocol number when we add a new PCM format definition. I guess it's not, as the ABI behavior itself doesn't change, but I might have overlooked some possible breakage.
thanks,
Takashi