[PATCH AUTOSEL 5.4 056/130] ALSA: usb-audio: Don't call usb_set_interface() at trigger callback

Sasha Levin
2020-12-23T02:59:24Z

From: Takashi Iwai <tiwai@suse.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@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>
Signed-off-by: Sasha Levin <sashal@kernel.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 49ad4e7bb70b5..87389ab69b5ee 100644
--- 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;
@@ -512,6 +497,19 @@ 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