[linux-audio-dev] USB-MIDI Transfer rate

Jens M Andreasen jens.andreasen at chello.se
Wed Sep 21 12:31:40 EDT 2005

On Wed, 2005-09-21 at 09:54 +0200, Clemens Ladisch wrote:

> It seems the usb-midi driver grabbed the device first.  Disable it in
> the kernel configuration, or put the line
> usb-midi
> into the /etc/hotplug/blacklist file.


Now to get back to the subject. By changing

        ep->max_transfer = usb_maxpacket(umidi->chip->dev, pipe, 1);

in the snd_usbmidi_out_endpoint_create function in usbmidi.c to:

        ep->max_transfer = 512;

.. I get a 16 fold increase in thruput.

Test data was a SysEx dump for upgrading the firmware which used take
~25 sec, now ~1.6 sec. The cute little LCD progress animation isn't
really visible anymore, but the update appears to be intact.

mvh // Jens M Andreasen

> Clemens

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