Re: [Alsa-devel] snd-usb-audio driver

[Greg KH <greg@kroah.com>]

On Mon, May 09, 2005 at 09:41:19AM +0200, Clemens Ladisch wrote:
> Greg KH wrote:
> > On Fri, Apr 29, 2005 at 05:01:42PM -0400, David Zeuthen wrote:
> > > On Fri, 2005-04-29 at 13:09 -0700, Greg KH wrote:
> > > > You can do this, as you get two different hotplug events.  This is
> > > > because usb drivers bind to the USB inteface, not the main device
> > > > itself.
> > >
> > > As an unrelated note this is actually not true for snd-usb-audio driver
> > >
> > >         [davidz@daxter hal]$ ls -l /sys/class/sound/pcmC2D0c/
> > >         total 0
> > >         -r--r--r--  1 root root 4096 Apr 29 16:57 dev
> > >         lrwxrwxrwx  1 root root    0 Apr 29 16:57 device ->
> > > ../../../devices/pci0000:00/0000:00:1d.1/usb3/3-2
> >
> > This should point to the interface, not the device, you are correct.
> >
> > >         [davidz@daxter hal]$ tree /sys/bus/usb/drivers/snd-usb-audio/
> > >         /sys/bus/usb/drivers/snd-usb-audio/
> > >         |-- 3-2:1.0 -> ../../../../devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2:1.0
> > >         |-- 3-2:1.1 -> ../../../../devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2:1.1
> > >         |-- 3-2:1.2 -> ../../../../devices/pci0000:00/0000:00:1d.1/usb3/3-2/3-2:1.2
> > >         `-- module -> ../../../../module/snd_usb_audio
> > >
> > > That"s a bug, right? Is this the right place to report it?
> >
> > Bug in the alsa driver, I suggest reporting it to them.  Should be a one
> > line fix.
> 
> The ALSA framework currently has exactly one 'struct device' for all
> devices of a sound card.  If we want to bind to the respectively
> correct interface for each device we have to change more than one
> line.
> 
> I'll make a temporary fix to bind to the first interface that is
> probed.

That will not work a usb speaker device that has the first interface as
the usb keyboard :)

Why not just point the struct device for ALSA at the struct
usb_interface that is passed to you?  That's the proper one to use.

thanks,

greg k-h


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