[alsa-devel] [PATCH] usb: add USB_QUIRK_RESET_RESUME for M-Audio 49

[Clemens Ladisch]

Jonathan Nieder wrote:
> Some USB MIDI keyboards fail to operate after a USB autosuspend.

Make that *all* USB MIDI devices with input ports.

This is not a bug in the device, but one of the many bugs introduced
with the autosuspend code in <http://git.kernel.org/linus/88a8516a2128>.

That patch does not handle input at all, i.e., when the driver wants to
read from the device, it just doesn't take it out of suspend mode.

> A workaround is to disable USB autosuspend for these devices by
> putting AUTOSUSPEND_USBID_BLACKLIST="0763:2027" (resp. 0763:019b) in
> /etc/laptop-mode/conf.d/usb-autosuspend.conf.  In the spirit of commit
> 166cb70e97bd ("usb: add USB_QUIRK_RESET_RESUME for M-Audio 88es"),
> reset the device on resume so this workaround is not needed any more.

It is not feasible to add the IDs of all USB MIDI devices.

I'm working on a fix that adds proper power management for input ports,
but this requires the driver to be reorganized a little ...


Regards,
Clemens