Messages in this thread | | | Subject | Re: [PATCH 1/2] ALSA: pcm: add SNDRV_PCM_FORMAT_{S, U}20_4 | From | Takashi Sakamoto <> | Date | Thu, 23 Nov 2017 08:27:10 +0900 |
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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 <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/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
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