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 ;-)

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