[alsa-devel] [PATCH] ASoC: omap-pcm: Allow only formats with 1, 2, and 4 byte physical size

[Jyri Sarha]

On 03/03/2015 02:22 PM, Jarkko Nikula wrote:
> On Tue, Mar 03, 2015 at 01:41:21PM +0200, Peter Ujfalusi wrote:
>> On 03/03/2015 01:28 PM, Jyri Sarha wrote:
>>> sDMA support only transfer elements with 1, 2, and 4 byte physical
>>> size. Initialize the pcm driver accordingly.
>>
>> Acked-by: Peter Ujfalusi <peter.ujfalusi at ti.com>
>>
>>>
>>> Signed-off-by: Jyri Sarha <jsarha at ti.com>
>>> ---
>>>   sound/soc/omap/omap-pcm.c | 21 ++++++++++++++++++++-
>>>   1 file changed, 20 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/sound/soc/omap/omap-pcm.c b/sound/soc/omap/omap-pcm.c
>>> index f4b05bc..e49ee23 100644
>>> --- a/sound/soc/omap/omap-pcm.c
>>> +++ b/sound/soc/omap/omap-pcm.c
>>> @@ -39,7 +39,7 @@
>>>   #define pcm_omap1510()	0
>>>   #endif
>>>
>>> -static const struct snd_pcm_hardware omap_pcm_hardware = {
>>> +static struct snd_pcm_hardware omap_pcm_hardware = {
>>>   	.info			= SNDRV_PCM_INFO_MMAP |
>>>   				  SNDRV_PCM_INFO_MMAP_VALID |
>>>   				  SNDRV_PCM_INFO_INTERLEAVED |
>>> @@ -53,6 +53,24 @@ static const struct snd_pcm_hardware omap_pcm_hardware = {
>>>   	.buffer_bytes_max	= 128 * 1024,
>>>   };
>>>
>>> +/* sDMA supports only 1, 2, and 4 byte transfer elements. */
>>> +static void omap_pcm_limit_supported_formats(void)
>>> +{
>>> +	int i;
>>> +
>>> +	for (i = 0; i < SNDRV_PCM_FORMAT_LAST; i++) {
>>> +		switch (snd_pcm_format_physical_width(i)) {
>>> +		case 8:
>>> +		case 16:
>>> +		case 32:
>>> +			omap_pcm_hardware.formats |= (1LL << i);
>>> +			break;
>>> +		default:
>>> +			break;
>>> +		}
>>> +	}
>>> +}
>>> +
>
> I wonder why these are set in a loop instead of setting formats statically
> and why this is needed after commit 60e21d287344 ("ASoC: omap: Don't set
> unused struct snd_pcm_hardware fields")?
>


Hmmm, interesting. The the problem I was trying to solve was "read 
error: Cannot allocate memory" when trying to play S24_3LE format. With 
this patch the error is more informative:

aplay: set_params:1233: Sample format non available
Available formats:
- S16_LE
- S24_LE
- S32_LE

So the comment of commit 60e21d287344 is not entirely true, as far as I 
understand.

Best regards,
Jyri