[PATCH 115/241] ALSA: ua101, usx2y: fix broken MIDI output

Herton Ronaldo Krzesinski herton.krzesinski at canonical.com
Thu Dec 13 13:58:00 UTC 2012 -stable review patch.  If anyone has any objections, please let me know.


From: Clemens Ladisch <clemens at ladisch.de>

commit e99ddfde6ae0dd2662bb40435696002b590e4057 upstream.

Commit 88a8516a2128 (ALSA: usbaudio: implement USB autosuspend) added
autosuspend code to all files making up the snd-usb-audio driver.
However, midi.c is part of snd-usb-lib and is also used by other
drivers, not all of which support autosuspend.  Thus, calls to
usb_autopm_get_interface() could fail, and this unexpected error would
result in the MIDI output being completely unusable.

Make it work by ignoring the error that is expected with drivers that do
not support autosuspend.

Reported-by: Colin Fletcher <colin.m.fletcher at googlemail.com>
Reported-by: Devin Venable <venable.devin at gmail.com>
Reported-by: Dr Nick Bailey <nicholas.bailey at glasgow.ac.uk>
Reported-by: Jannis Achstetter <jannis_achstetter at web.de>
Reported-by: Rui Nuno Capela <rncbc at rncbc.org>
Cc: Oliver Neukum <oliver at neukum.org>
Signed-off-by: Clemens Ladisch <clemens at ladisch.de>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
 sound/usb/midi.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/sound/usb/midi.c b/sound/usb/midi.c
index c83f614..eeefbce 100644
--- a/sound/usb/midi.c
+++ b/sound/usb/midi.c
@@ -148,6 +148,7 @@ struct snd_usb_midi_out_endpoint {
 		struct snd_usb_midi_out_endpoint* ep;
 		struct snd_rawmidi_substream *substream;
 		int active;
+		bool autopm_reference;
 		uint8_t cable;		/* cable number << 4 */
 		uint8_t state;
 #define STATE_UNKNOWN	0
@@ -1076,7 +1077,8 @@ static int snd_usbmidi_output_open(struct snd_rawmidi_substream *substream)
 		return -ENXIO;
 	err = usb_autopm_get_interface(umidi->iface);
-	if (err < 0)
+	port->autopm_reference = err >= 0;
+	if (err < 0 && err != -EACCES)
 		return -EIO;
 	substream->runtime->private_data = port;
 	port->state = STATE_UNKNOWN;
@@ -1087,9 +1089,11 @@ static int snd_usbmidi_output_open(struct snd_rawmidi_substream *substream)
 static int snd_usbmidi_output_close(struct snd_rawmidi_substream *substream)
 	struct snd_usb_midi* umidi = substream->rmidi->private_data;
+	struct usbmidi_out_port *port = substream->runtime->private_data;
 	substream_open(substream, 0);
-	usb_autopm_put_interface(umidi->iface);
+	if (port->autopm_reference)
+		usb_autopm_put_interface(umidi->iface);
 	return 0;

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