ALSA: usb-audio: Don't call usb_set_interface() at trigger callback

The PCM trigger callback is atomic, hence we must not call a function
like usb_set_interface() there.  Calling it from there would lead to a
kernel Oops.

Fix it by moving the usb_set_interface() call to set_sync_endpoint().

Also, apply the snd_usb_set_interface_quirk() for consistency, too.

Tested-by: Keith Milner <kamilner@superlative.org>
Tested-by: Dylan Robinson <dylan_robinson@motu.com>
Link: https://lore.kernel.org/r/20201123085347.19667-3-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 3265155..380d727 100644 (file)
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -232,21 +232,6 @@ static int start_endpoints(struct snd_usb_substream *subs)
            !test_and_set_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags)) {
                struct snd_usb_endpoint *ep = subs->sync_endpoint;
 
-               if (subs->data_endpoint->iface != subs->sync_endpoint->iface ||
-                   subs->data_endpoint->altsetting != subs->sync_endpoint->altsetting) {
-                       err = usb_set_interface(subs->dev,
-                                               subs->sync_endpoint->iface,
-                                               subs->sync_endpoint->altsetting);
-                       if (err < 0) {
-                               clear_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags);
-                               dev_err(&subs->dev->dev,
-                                          "%d:%d: cannot set interface (%d)\n",
-                                          subs->sync_endpoint->iface,
-                                          subs->sync_endpoint->altsetting, err);
-                               return -EIO;
-                       }
-               }
-
                dev_dbg(&subs->dev->dev, "Starting sync EP @%p\n", ep);
 
                ep->sync_slave = subs->data_endpoint;
@@ -530,6 +515,19 @@ static int set_sync_endpoint(struct snd_usb_substream *subs,
 
        subs->data_endpoint->sync_master = subs->sync_endpoint;
 
+       if (subs->data_endpoint->iface != subs->sync_endpoint->iface ||
+           subs->data_endpoint->altsetting != subs->sync_endpoint->altsetting) {
+               err = usb_set_interface(subs->dev,
+                                       subs->sync_endpoint->iface,
+                                       subs->sync_endpoint->altsetting);
+               if (err < 0)
+                       return err;
+               dev_dbg(&dev->dev, "setting usb interface %d:%d\n",
+                       subs->sync_endpoint->iface,
+                       subs->sync_endpoint->altsetting);
+               snd_usb_set_interface_quirk(dev);
+       }
+
        return 0;
 }