ALSA: usb-audio: Fix autopm error during probing

commit 60af3d037eb8c670dcce31401501d1271e7c5d95 upstream.

We've got strange errors in get_ctl_value() in mixer.c during
probing, e.g. on Hercules RMX2 DJ Controller:

  ALSA mixer.c:352 cannot get ctl value: req = 0x83, wValue = 0x201, wIndex = 0xa00, type = 4
  ALSA mixer.c:352 cannot get ctl value: req = 0x83, wValue = 0x200, wIndex = 0xa00, type = 4
  ....

It turned out that the culprit is autopm: snd_usb_autoresume() returns
-ENODEV when called during card->probing = 1.

Since the call itself during card->probing = 1 is valid, let's fix the
return value of snd_usb_autoresume() as success.

Reported-and-tested-by: Daniel Schürmann <daschuer@mixxx.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 566acb3..acb7fac 100644 (file)
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -611,7 +611,9 @@ int snd_usb_autoresume(struct snd_usb_audio *chip)
        int err = -ENODEV;
 
        down_read(&chip->shutdown_rwsem);
        int err = -ENODEV;
 
        down_read(&chip->shutdown_rwsem);

-       if (!chip->shutdown && !chip->probing)
+       if (chip->probing)
+               err = 0;
+       else if (!chip->shutdown)

                err = usb_autopm_get_interface(chip->pm_intf);
        up_read(&chip->shutdown_rwsem);
 
                err = usb_autopm_get_interface(chip->pm_intf);
        up_read(&chip->shutdown_rwsem);