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

[Clemens Ladisch <clemens@ladisch.de>]

Takashi Iwai wrote:> At Sun, 25 Nov 2012 23:01:27 +0100,
> Clemens Ladisch wrote:
>>
>> 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 ...
>
> Doesn't a simple patch like below work?

> +static int substream_open(struct snd_rawmidi_substream *substream, int open)
>  {
> +	if (open && umidi->opened++ == 0) {
> +		err = usb_autopm_get_interface(umidi->iface);
>
>  static int snd_usbmidi_input_open(struct snd_rawmidi_substream *substream)
>  {
> +	return substream_open(substream, 1);

No, because the input URBs are submitted before the userspace device is
opened.  (And usb_autopm_get_interface() cannot be called from the USB
probe callback.)


Regards,
Clemens