On Nov 23 2017 04:17, 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 <m...@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/uapi/sound/asound.h b/include/uapi/sound/asound.h index c227ccba60ae..69b661816491 100644 --- a/include/uapi/sound/asound.h +++ b/include/uapi/sound/asound.h @@ -236,7 +236,11 @@ typedef int __bitwise snd_pcm_format_t; #define SNDRV_PCM_FORMAT_DSD_U32_LE ((__force snd_pcm_format_t) 50) /* DSD, 4-byte samples DSD (x32), little endian */ #define SNDRV_PCM_FORMAT_DSD_U16_BE ((__force snd_pcm_format_t) 51) /* DSD, 2-byte samples DSD (x16), big endian */ #define SNDRV_PCM_FORMAT_DSD_U32_BE ((__force snd_pcm_format_t) 52) /* DSD, 4-byte samples DSD (x32), big endian */ -#define SNDRV_PCM_FORMAT_LAST SNDRV_PCM_FORMAT_DSD_U32_BE +#define SNDRV_PCM_FORMAT_S20_4LE ((__force snd_pcm_format_t) 53) /* in four bytes */ +#define SNDRV_PCM_FORMAT_S20_4BE ((__force snd_pcm_format_t) 54) /* in four bytes */ +#define SNDRV_PCM_FORMAT_U20_4LE ((__force snd_pcm_format_t) 55) /* in four bytes */ +#define SNDRV_PCM_FORMAT_U20_4BE ((__force snd_pcm_format_t) 56) /* in four bytes */ +#define SNDRV_PCM_FORMAT_LAST SNDRV_PCM_FORMAT_U20_4BE
In my opinion, for this type of definition, it's better to declare left/right-adjusted or padding side. (Of course, silence definition is already a hint, however the lack of information forces developers to have a careful behaviour to handle entries on the list.)
(I note that in current ALSA PCM interface there's no way to deliver MSB/LSB-first information about sample format.)
Additionally, alsa-lib includes some codes related to the definition[1]. If you'd like to thing goes well out of ALSA SoC part, it's better to submit changes to the library as well.
[1] http://git.alsa-project.org/?p=alsa-lib.git;a=blob;f=src/pcm/pcm_misc.c;h=5420b1895713a3aec3624a5218794a7b49baf167;hb=HEAD
Regards Takashi Sakamoto
