Re: Kernel 2.6.22 some Logitech webcams

On Thu, 4 Oct 2007, Laurent Pinchart wrote:

> Hi everybody,
> 
> I recently noticed a regression when upgrading to 2.6.22. I narrowed the 
> problem to the "[ALSA] usbaudio - Fix Oops with broken usb descriptors" patch 
> (SHA1 ID beb60119bcc9cbd80bc5b4f7feec419e067d3e46).
> 
> With this patch applied, the uvcvideo driver (http://linux-uvc.berlios.de) 
> fails to initialise the video interface with first and second generation 
> Logitech UVC webcams.
> 
> The problem can be worked around by associating the usbaudio driver with the 
> device before the uvcvideo driver quicks in. As the device descriptors list 
> the video interface before the audio interface, this can only be achieved by 
> deinstalling the uvcvideo driver and loading it manually after the usbaudio 
> driver has initialised the audio interface.
> 
> Devices are probably faulty, as they are known to have some firmware bugs 
> related to timings (confirmed by the vendor). The above patch does the right 
> thing, but breaks broken devices that worked by chance up to 2.6.21.
> 
> I'm open to ideas regarding a way to fix the problem. For what it's worth, the 
> webcams work fine under Windows (most probably because the Windows USB stack 
> is slower when dealing with control requests).

Do you want to prevent the uvcvideo driver from binding to the audio 
interfaces in the bad devices?  Maybe a small blacklist would work.

Alan Stern


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