On 20.04.2022 12:15, Sascha Hauer wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>
> Hi,
Hi Sascha,
>
> On Mon, Mar 07, 2022 at 02:21:57PM +0200, Codrin Ciubotariu wrote:
>> Even if struct snd_dmaengine_pcm_config is used, prepare_slave_config()
>> callback might not be set. Check if this callback is set before using it.
>>
>> Fixes: fa654e085300 ("ASoC: dmaengine-pcm: Provide default config")
>> Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@xxxxxxxxxxxxx>
>> ---
>>
>> Changes in v2,v3:
>> - none
>>
>> sound/soc/soc-generic-dmaengine-pcm.c | 6 +++---
>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/sound/soc/soc-generic-dmaengine-pcm.c b/sound/soc/soc-generic-dmaengine-pcm.c
>> index 285441d6aeed..2ab2ddc1294d 100644
>> --- a/sound/soc/soc-generic-dmaengine-pcm.c
>> +++ b/sound/soc/soc-generic-dmaengine-pcm.c
>> @@ -86,10 +86,10 @@ static int dmaengine_pcm_hw_params(struct snd_soc_component *component,
>>
>> memset(&slave_config, 0, sizeof(slave_config));
>>
>> - if (!pcm->config)
>> - prepare_slave_config = snd_dmaengine_pcm_prepare_slave_config;
>> - else
>> + if (pcm->config && pcm->config->prepare_slave_config)
>> prepare_slave_config = pcm->config->prepare_slave_config;
>> + else
>> + prepare_slave_config = snd_dmaengine_pcm_prepare_slave_config;
>>
>> if (prepare_slave_config) {
>> int ret = prepare_slave_config(substream, params, &slave_config);
>
> I wonder if this patch is correct. There are drivers like
> sound/soc/mxs/mxs-pcm.c which call snd_dmaengine_pcm_register() with a
> config which has the prepare_slave_config callback unset. For these
> drivers dmaengine_pcm_hw_params() previously was a no-op. Now with this
> patch snd_dmaengine_pcm_prepare_slave_config() and
> dmaengine_slave_config() are called. At least for the mxs-pcm driver
> calling dmaengine_slave_config() will return -ENOSYS.
>
> At least the "Check if this callback is set before using it" part is
> wrong, the callback is checked before using it with
>
> if (prepare_slave_config) {
> ...
> }
>
> I don't have any mxs hardware at hand to test this. I just stumbled upon
> the change of behaviour when rebasing
> https://patchwork.kernel.org/project/alsa-devel/patch/20220301122111.1073174-1-s.hauer@xxxxxxxxxxxxxx/
> on current master.
You are right. I changed the behavior from:
if (pmc->config && !pcm->config->prepare_slave_config)
<do nothing>
to:
if (pmc->config && !pcm->config->prepare_slave_config)
snd_dmaengine_pcm_prepare_slave_config()
It was not intended and I agree that the commit message is not accurate.
I guess some drivers might not need dmaengine_slave_config()...
However, in my case, for the mchp-pdmc driver, I do have pcm->config
with pcm->config->prepare_slave_config NULL, but I still need
snd_dmaengine_pcm_prepare_slave_config() to be called. Should we add a
separate flag to call snd_dmaengine_pcm_prepare_slave_config() if
pcm->config->prepare_slave_config is NULL?
Nice catch!
Best regards,
Codrin
