Some idea about usb audio gadget driver.

Some idea about usb audio gadget driver.

[Bryan Wu]

Hi ALSA and USB folks,

I plan to develop a usb audio gadget driver on Blackfin platform (can
be shared for other embedded system).

 - A new usb gadget driver which recognized by Linux/Windows PC as an
USB audio card.
 - There is an ALSA sound card on the same embedded device.
 - The usb gadget driver receives audio data from host and send them
to ALSA sound card to playback
 - The usb gadget driver send the audio data recorded by ALSA sound
card to host as recording.
 - The usb gadget driver response to some audio card control command
such as volume/mute control

Questions,

 - Is there any similar things on this planet?
 - How about gmidi usb midi gadget driver?
 - How can I open/playback/record/close a ALSA sound card in kernel
space not using alsalib in user space?

Thanks a lot
-Bryan
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: Some idea about usb audio gadget driver.

[Felipe Balbi]

On Tue, Sep 23, 2008 at 05:50:33PM +0800, ext Bryan Wu wrote:
> Hi ALSA and USB folks,
> 
> I plan to develop a usb audio gadget driver on Blackfin platform (can
> be shared for other embedded system).
> 
>  - A new usb gadget driver which recognized by Linux/Windows PC as an
> USB audio card.
>  - There is an ALSA sound card on the same embedded device.
>  - The usb gadget driver receives audio data from host and send them
> to ALSA sound card to playback
>  - The usb gadget driver send the audio data recorded by ALSA sound
> card to host as recording.
>  - The usb gadget driver response to some audio card control command
> such as volume/mute control
> 
> Questions,
> 
>  - Is there any similar things on this planet?
>  - How about gmidi usb midi gadget driver?
>  - How can I open/playback/record/close a ALSA sound card in kernel
> space not using alsalib in user space?

Start by converting gmidi to composite framework. Separate the alsa
generic code from usb generic code and the function driver (in that case
MIDI). Then, all you have to do is add a new function driver with proper
audio streaming.

Later on someone might be interested in adding mic support ;-)

-- 
balbi

Re: Some idea about usb audio gadget driver.

[Matthieu CASTET]

Felipe Balbi a écrit :
> On Tue, Sep 23, 2008 at 05:50:33PM +0800, ext Bryan Wu wrote:
>> Hi ALSA and USB folks,
>>
>>
>>  - Is there any similar things on this planet?
>>  - How about gmidi usb midi gadget driver?
>>  - How can I open/playback/record/close a ALSA sound card in kernel
>> space not using alsalib in user space?
> 
> Start by converting gmidi to composite framework. Separate the alsa
> generic code from usb generic code and the function driver (in that case
> MIDI). Then, all you have to do is add a new function driver with proper
> audio streaming.
I am not sure there is lot's of common alsa code. IIRC Midi and Pcm API
are different in alsa.

But I think we shouldn't try to drive a sound card from kernel, we
should create an alsa sound card like gmidi, and let's userspace do what
it wants (redirect from/to another sound card, stream files, ...).


Mattieu

Re: [alsa-devel] Some idea about usb audio gadget driver.

[Clemens Ladisch]

Bryan Wu wrote:
>  - A new usb gadget driver which recognized by Linux/Windows PC as an
> USB audio card.
>  - There is an ALSA sound card on the same embedded device.
>  - The usb gadget driver receives audio data from host and send them
> to ALSA sound card to playback
> ...
>  - Is there any similar things on this planet?
>  - How about gmidi usb midi gadget driver?

gmidi does not access other sound cards; it makes the USB MIDI interface
available to userspace.

>  - How can I open/playback/record/close a ALSA sound card in kernel
> space not using alsalib in user space?

If you really want to do this in the kernel, have a look at the OSS
emulation (sound/core/oss/).


Regards,
Clemens
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html