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Date:   Tue, 22 Dec 2020 21:23:50 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Takashi Iwai <tiwai@...e.de>,
        Keith Milner <kamilner@...erlative.org>,
        Dylan Robinson <dylan_robinson@...u.com>,
        Sasha Levin <sashal@...nel.org>, alsa-devel@...a-project.org
Subject: [PATCH AUTOSEL 4.9 22/48] ALSA: usb-audio: Don't call usb_set_interface() at trigger callback

From: Takashi Iwai <tiwai@...e.de>

[ Upstream commit 4974b7950929e4a28d4eaee48e4ad07f168ac132 ]

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@...erlative.org>
Tested-by: Dylan Robinson <dylan_robinson@...u.com>
Link: https://lore.kernel.org/r/20201123085347.19667-3-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 sound/usb/pcm.c | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 95d02e25a3133..77c704847e4ac 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -242,21 +242,6 @@ 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;
@@ -499,6 +484,19 @@ 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;
 }
 
-- 
2.27.0

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