[alsa-devel] sound: usb-audio: full capture/playback/spdif support for Digidesign Mbox 2
tiwai at suse.de
Thu Dec 13 08:01:40 CET 2012
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
> 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.
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