[alsa-devel] [RFC PATCH 01/11] ALSA: implement MEDIA_IOC_DEVICE_INFO

Clemens Ladisch clemens at ladisch.de
Fri Sep 7 09:14:30 CEST 2012

Mark Brown wrote:
> On Tue, Aug 28, 2012 at 12:29:33AM +0200, Clemens Ladisch wrote:
>> +config SND_MEDIA
>> +	bool "Media Controller API (EXPERIMENTAL)"
>> +	depends on EXPERIMENTAL
>> +	help
>> +	  Say Y here to enable the media controller API, which allows to
>> +	  retrieve the internal topology of sound devices.
> I think there's a general consensus these days that EXPERIMENTAL is
> pretty meaningless so we probably shouldn't bother with it.

Well, I couldn't claim this to be any less experimental than the
implementation in drivers/media/.  :)

> The text is also a bit confusing, it enables use of the media
> controller API for ALSA devices really.

It's in the ALSA menu.  I could put "ALSA" in the title if it helps.

> I have to say I'm also a bit surprised that there's no core framework
> for media controller and we're open coding ioctl() implementations here,

drivers/media/media-*.c exists, but I did not use that implementation
because someone expressed concern about it being too heavyweight ...

> I'd have thought there would at least be a way of enumerating all media
> controller devices in the system...

It appears userspace is supposed to check all /dev/media* devices.
(Using /dev/snd/controlC* is just a makeshift arrangement; I'll have to
reuse some part of the media device registration framework, or tell udev
to create symlinks.)


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