[alsa-devel] Device creation order

Jaroslav Kysela perex at perex.cz
Fri Apr 3 09:50:47 CEST 2009

On Fri, 3 Apr 2009, Clemens Ladisch wrote:

> Jaroslav Kysela wrote:
>> Unfortunately, driver may use more complex scenarios like:
>> - some hardware requires additional firmware - in this case devices
>>    might be created, but they are not useable until firmware is loaded
> This is only true for drivers that load firmware with a hwdep device
> instead of using request_firmware().  Is there any driver that has not
> yet been converted?  *grep*  ... except usx2y?

Good point.

>> - dynamic device creation at runtime - for example we have an
>>    experimental HDA driver configuration code which might change
>>    the arrangement of PCM devices on request from the user space
>> I would suggest to wait awhile with some small timeout (0.5 sec?) for all
>> devices to get the usual static arrangement working and handle extra
>> dynamic cases, too.
> The current implementation of the ALSA framework guarantees that the
> control device file is that latest one to be created for all the devices
> created at initialization.  Any devices created later depend on some
> userspace action, so a small timeout won't help in this case.

The timeout might help to let alsactl utility to initialize the 
soundcard's mixer. But I agree that alsactl should send a HAL message that 
initial setting was done instead.


Jaroslav Kysela <perex at perex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.

More information about the Alsa-devel mailing list