[PATCH 6.18 040/314] ALSA: usb-audio: Cap the packet size pre-calculations

Sasha Levin
2026-03-10T11:25:16Z

From: Takashi Iwai <tiwai@suse.de>

[ Upstream commit 7fe8dec3f628e9779f1631576f8e693370050348 ]

We calculate the possible packet sizes beforehand for adaptive and
synchronous endpoints, but we didn't take care of the max frame size
for those pre-calculated values. When a device or a bus limits the
packet size, a high sample rate or a high number of channels may lead
to the packet sizes that are larger than the given limit, which
results in an error from the USB core at submitting URBs.

As a simple workaround, just add the sanity checks of pre-calculated
packet sizes to have the upper boundary of ep->maxframesize.

Fixes: f0bd62b64016 ("ALSA: usb-audio: Improve frames size computation")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=221076
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Link: https://patch.msgid.link/20260225085233.316306-2-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
sound/usb/endpoint.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 3ac1fbec6327e..173edce027d7b 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -1374,6 +1374,9 @@ int snd_usb_endpoint_set_params(struct snd_usb_audio *chip,
return -EINVAL;
}

+ ep->packsize[0] = min(ep->packsize[0], ep->maxframesize);
+ ep->packsize[1] = min(ep->packsize[1], ep->maxframesize);
+
/* calculate the frequency in 16.16 format */
ep->freqm = ep->freqn;
ep->freqshift = INT_MIN;
--
2.51.0