[alsa-devel] ASoC: Failed to create DAPM debugfs

[Lars-Peter Clausen]

On 04/09/2015 10:22 AM, Nicolin Chen wrote:
> On Thu, Apr 09, 2015 at 09:39:09AM +0200, Lars-Peter Clausen wrote:
>
>> The whole thing is a bit confusing. The message you get is what
>> you'd get if the 'dapm' sub-directory in the card debugfs directory
>> can not be created. One of the few reasons why it would fail is if
>> it already existed, but we should never register two dapm contexts
>> for the card, so that's a bit strange. One of the few reasons I can
>> imagine this could happen is if the parent directory could not be
>> created and now we try to create multiple dapm directories at the
>> top-level.
>>
>> Try to do some more debugging and see why and where exactly things
>> go wrong. Can you also try this:
>>
>> diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
>> index b6f8820..7810262 100644
>> --- a/sound/soc/soc-dapm.c
>> +++ b/sound/soc/soc-dapm.c
>> @@ -1898,6 +1898,11 @@
>>   {
>>   	struct dentry *d;
>>
>> +	if (!parent) {
>> +		dev_warn(dapm->dev, "No debugfs parent!\n");
>
> I tried, yes, the parent is NULL. And I did a little tracing and found
> that the card->debugfs_root, which is NULL, should be initialized in
> the soc_init_card_debugfs() while snd_soc_dapm_debugfs_init() seems
> to access this card->debugfs_root before calling soc_init_card_debugfs().
>
> I think I must have missed something over here....

Looks like this is the culprit: 
http://git.kernel.org/cgit/linux/kernel/git/broonie/sound.git/commit/?h=for-next&id=4e2576bd36a12e78ac3786d05b99a820dffe687f