Re: [PATCH 2/2] ALSA: usb-audio: Fix missing autopm for MIDI input

[Clemens Ladisch <clemens@ladisch.de>]

Takashi Iwai wrote:
> The commit [88a8516a: ALSA: usbaudio: implement USB autosuspend] added
> the support of autopm for USB MIDI output, but it didn't take the MIDI
> input into account.
>
> This patch adds the following for fixing the autopm:
> - Manage the URB start at the first MIDI input stream open, instead of
>   the time of instance creation
> - Move autopm code to the common substream_open()
> - Make snd_usbmidi_input_start/_stop() more robust and add the running
>   state check
>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Takashi Iwai <tiwai@suse.de>
> ...
> +static int substream_open(struct snd_rawmidi_substream *substream, int dir,
> +			  int open)
>  {
>  	struct snd_usb_midi* umidi = substream->rmidi->private_data;
>  	struct snd_kcontrol *ctl;
> +	int err;
>
>  	down_read(&umidi->disc_rwsem);
>  	if (umidi->disconnected) {
>  		up_read(&umidi->disc_rwsem);
> +		return open ? -ENODEV : 0;
>  	}
>
>  	mutex_lock(&umidi->mutex);
>  	if (open) {
> +		if (!umidi->opened[0] && !umidi->opened[1]) {
> +			err = usb_autopm_get_interface(umidi->iface);
> +			umidi->autopm_reference = err >= 0;
> +			if (err < 0 && err != -EACCES) {
> +				up_read(&umidi->disc_rwsem);
> +				return -EIO;

umidi->mutex is still held here.

Otherwise, for both patches:
Reviewd-by: Clemens Ladisch <clemens@ladisch.de>
Tested-by: Clemens Ladisch <clemens@ladisch.de>


Regards,
Clemens