[alsa-devel] [PATCH] ALSA: usb: Work around CM6631 sample rate change bug

Clemens Ladisch clemens at ladisch.de
Tue Mar 5 22:39:55 CET 2013

Torstein Hegge wrote:
> On Tue, Mar 05, 2013 at 11:35:35AM +0100, Clemens Ladisch wrote:
>> Torstein Hegge wrote:
>>> On Tue, Mar 05, 2013 at 08:55:03AM +0100, Clemens Ladisch wrote:
>>>> From that driver's .inf file:
>>>> %CMUACWO.DeviceDesc%=CMUACWO,USB\VID_0D8C&PID_0301&MI_00
>>>> %CMUACWO.DeviceDesc%=CMUACWO,USB\VID_0D8C&PID_0302&MI_00
>>>> %CMUACWO.DeviceDesc%=CMUACWO,USB\VID_0D8C&PID_0304&MI_00
>>>> %CMUACWO.DeviceDesc%=CMUACWO,USB\VID_0D8C&PID_0305&MI_00
>>>> %CMUACWO.DeviceDesc%=CMUACWO,USB\VID_0D8C&PID_0306&MI_00
>>>> %CMUACWO.DeviceDesc%=CMUACWO,USB\VID_0D8C&PID_0309&MI_00
>>>> %CMUACWO.DeviceDesc%=CMUACWO,USB\VID_0D8C&PID_0310&MI_00
>>>> %CMUACWO.DeviceDesc%=CMUACWO,USB\VID_0D8C&PID_0311&MI_00	;CM6610A
>>>> %CMUACWO.DeviceDesc%=CMUACWO,USB\VID_0D8C&PID_0312&MI_00	;CM6620A
>>>> %CMUACWO.DeviceDesc%=CMUACWO,USB\VID_0D8C&PID_0313&MI_00	;CM6630A
>>>> %CMUACWO.DeviceDesc%=CMUACWO,USB\VID_0D8C&PID_0314&MI_00	;CM6631A
>>>> %CMUACWO.DeviceDesc%=CMUACWO,USB\VID_0D8C&PID_0319&MI_00	;CM6631A
>>>> %CMUACWO.DeviceDesc%=CMUACWO,USB\VID_0D8C&PID_0315&MI_00	;CM6632A
>>>> %CMUACWO.DeviceDesc%=CMUACWO,USB\VID_200C&PID_1030&MI_00
>>>> %CMUACWO.DeviceDesc%=CMUACWO,USB\VID_054C&PID_06CF&MI_00
>>> I'm not quite sure how to interpret that. I guess most of those are
>>> similar devices that doesn't necessarily need this workaround?
>> Those are all the IDs that the C-Media driver attaches to.  The
>> hardware is always the same; I would be surprised if the firmware
>> did not have the same bug.
> The ids listed covers CM6610, CM6620 and CM6631, which are distinct
> pieces of hardware, or at least they are sold as if they were.

All the same chip with different labels.  I don't know if C-Media even
bothers to fuse off the unused features in the lower models.

> It might be a fair assumption that all current C-Media UAC V2.0 devices
> have this issue.

Indeed.  In any case, re-setting the interface should not hurt *any*
compliant device.


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