[alsa-devel] sound: usb-audio: full capture/playback/spdif support for Digidesign Mbox 2

[Takashi Iwai]

At Thu, 13 Dec 2012 17:21:55 +1100,
Damien Zammit wrote:
> 
> Hi I thought I would post an update on this thread.
> I realise it is quite old but what I have now is relevant.
> 
> /*
>  * Digidesign Mbox 2
>  *
>  * Interface list:
>  * 0    Firmware
>  * 1    Control
>  * 2    Playback        (Async)
>  * 3    IEC958                  (Ignore)
>  * 4    Record          (Sync)
>  * 5    Record          (Async) (Ignore)
>  * 6    MIDI
>  *
>  */
> 
> My previous posts may have demonstrated a lack of understanding of how
> USB audio devices work, but I believe I have learnt a bit more since
> last time I posted.
> 
> I have determined that there is a combination of altsettings for this
> device that allows hardcoding of them and still provides duplex
> support, ie, the fact that it supports multiple endpoints is
> irrelevant.
> If you use interfaces 2 and 4 both with #2 altsetting, hardcode the
> samplerate to 48000Hz (max) and the bit depth at 24 (max) and send
> some control magic to set it up, it works great!
> 
> It also requires a boot quirk to load firmware into the device from an
> onboard memory chip.  I determined the control sequence to do so but
> it also needs a 3 second delay while the firmware activates and I dont
> have the knowledge to do a proper in-kernel delay.
> 
> In summary there are 3 parts to make this device work:
> 1) Boot quirk - load firmware and wait 3 seconds
> 2) Set up samplerate/bitrate in the device once and force S24_3BE format.
> 3) Select interfaces 2 and 4 both with altsetting 2, and interface 6 for midi.
> 
> I can provide working code for all three steps (except the waiting
> part is dodgey).  I can't submit a proper patch.

Why not...?


Takashi