[alsa-devel] How to add a new MIDI device to the usbaudio driver

[Daniel Mack]

On Tue, Aug 23, 2011 at 1:57 PM, Kristian Amlie <kristian at amlie.name> wrote:
> I was not able to to use 31250 baud as you suggested. However, I tried
> 38400 baud, and that seemed to work. I got a small number of bytes
> everytime I pressed a key on the instrument.
>
> Using the following command line:
>
> $ cu -s 38400 -l /dev/ttyUSB0 | hexdump -C
>
> and pressing the same key repeatedly with the same force, I got the
> following output:
>
> 00000000  18 f9 ff 18 03 f8 18 f9  ff 18 01 f8 18 f9 ff 18
> |................|
> 00000010  01 f8 18 fb ff 18 01 f8  18 fb ff 18 01 f8 18 fb
> |................|
> 00000020  ff 18 03 f8 18 f9 ff 18  01 f8 18 fb ff 18 01 f8
> |................|
> 00000030  18 fb ff 18 01 f8 18 fb  ff 18 01 f8 07 43 6f 6e
> |.............Con|
> 00000040  6e 65 63 74 65 64 2e 0a  07 43 6f 6e 6e 65 63 74
> |nected...Connect|
> 00000050  65 64 2e 0a 0a 07 44 69  73 63 6f 6e 6e 65 63 74
> |ed....Disconnect|
> 00000060  65 64 2e 0a                                       |ed..|
> 00000064

That hexdump reads as "Connected....Disconnected". Are you sure you
get useful data from cu?

If you are certain about this, I would recommend you add some debug
printk() into drivers/usb/serial/ftdi_sio.c and trace what values the
functions change_speed() and update_mctrl() pass to usb_control_msg()
when the device is connected and cu is started. Once we have this
information, I can prepare a patch to add the control messages to the
MIDI driver.


Daniel