• Manuel Reinhardt's avatar
    ALSA: usb-audio: Add quirk for MOTU MicroBook II · a634090a
    Manuel Reinhardt authored
    Add an entry to the quirks-table to for usb-audio to recognize the
    Microbook II (although it only exposes vendor interfaces). A simple boot
    quirk is also implemented to set up the sample rate and  make sure that
    no audio urbs are sent before the device is ready.
    
    This patch only provides audio playback and capture at 96kHz sample
    rate. Notice the following shortcomings:
    
    - The sample rate is currently hardcoded to 96k although the device also
      supports 48k and 44.1k.
    
    - The various mixer controls of the MicroBook are not made available.
    
    - The keep-iface control should be on by default because the device
      shuts down whenever the altsetting is reset which is usually unwanted.
      (I don't know the best way to do this)
    
    - The communication format used by the MicroBook for sample rate setting
      and also other setup has been reverse engineered by looking at the
      usbmon output while running the windows driver through virtualbox. In
      this patch the first byte of every message is set to \0 while in the
      observed communications the first byte acts as a "message-counter"
      increasing its value with every message sent. Leaving it at \0 does
      not seem to affect the device.
    Signed-off-by: default avatarManuel Reinhardt <manuel.rhdt@gmail.com>
    Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
    a634090a
pcm.c 50 KB