From: Clemens Ladisch <clemens@ladisch.de>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: alsa-devel@alsa-project.org,
David Henningsson <david.henningsson@canonical.com>,
zonque@gmail.com
Subject: Re: USB Audio initialization race
Date: Sun, 15 Sep 2013 10:49:40 +0200 [thread overview]
Message-ID: <523574A4.4010203@ladisch.de> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1309142127140.6622-100000@netrider.rowland.org>
Alan Stern wrote:
> On Sat, 14 Sep 2013, Clemens Ladisch wrote:
>> Alan Stern wrote:
>>> So here's my question: If the sound driver recognizes that interface B
>>> is connected with interface A when B is probed, why can't it recognize
>>> this fact when A is probed? It could claim B while A's probe is
>>> running. Then the sound card would be registered with the PCM
>>> component already in place.
>>
>> The sound driver already does this.
>
> It does? Why does the comment preceding snd_usb_audio_probe() say:
>
> * thus we check the usb device pointer and creates the card instance
> * only at the first time. the successive calls of this function will
> * append the pcm interface to the corresponding card.
For UAC devices with correct descriptors, and for devices with multi-
interface quirks, the driver claims all interfaces at once. But it is
still possible to have devices with zero or two audio control interfaces.
Regards,
Clemens
next prev parent reply other threads:[~2013-09-15 8:50 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-13 19:56 USB Audio initialization race David Henningsson
2013-09-13 20:39 ` Alan Stern
2013-09-13 20:53 ` David Henningsson
2013-09-13 21:06 ` Alan Stern
2013-09-13 23:47 ` David Henningsson
2013-09-14 13:44 ` Alan Stern
2013-09-14 19:33 ` Clemens Ladisch
2013-09-15 1:35 ` Alan Stern
2013-09-15 8:49 ` Clemens Ladisch [this message]
2013-09-16 22:21 ` David Henningsson
2013-09-13 20:55 ` Clemens Ladisch
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