[PATCH 5.10.y v1] ALSA: usb-audio: Evaluate packsize caps at the right place

[PATCH 5.10.y v1] ALSA: usb-audio: Evaluate packsize caps at the right place

[pzqqt88198]

From: Takashi Iwai <tiwai@suse.de>

[ Upstream commit 52521e8398839105ef8eb22b3f0993f9b0d11a57 ]

We introduced the upper bound checks of the packet sizes by the
ep->maxframesize for avoiding the URB submission errors.  However, the
check was applied at an incorrect place in the function
snd_usb_endpoint_set_params() where ep->maxframesize isn't defined
yet; the value is defined at a bit later position.  So this ended up
with a failure at the first run while the second run works.

For fixing it, move the check at the correct place, right after the
calculation of ep->maxframesize in the same function.

Fixes: 7fe8dec3f628 ("ALSA: usb-audio: Cap the packet size pre-calculations")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=221292
Cc: <stable@vger.kernel.org>
Link: https://patch.msgid.link/20260410143220.1676344-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
[Pzqqt: Backport to 5.10]
Signed-off-by: Pzqqt <pzqqt88198@gmail.com>
---
 sound/usb/endpoint.c | 3 ---
 sound/usb/pcm.c      | 7 +++++++
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 8e2b90cb5b95..21bcdc811a81 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -1099,9 +1099,6 @@ int snd_usb_endpoint_set_params(struct snd_usb_endpoint *ep,
 		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;
diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index f4494d054917..802ed1dbd23b 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -953,6 +953,13 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
 	subs->data_endpoint->curframesize =
 		bytes_to_frames(runtime, subs->data_endpoint->curpacksize);
 
+	subs->data_endpoint->packsize[0] = min(
+		subs->data_endpoint->packsize[0],
+		subs->data_endpoint->maxframesize);
+	subs->data_endpoint->packsize[1] = min(
+		subs->data_endpoint->packsize[1],
+		subs->data_endpoint->maxframesize);
+
 	/* reset the pointer */
 	subs->hwptr_done = 0;
 	subs->transfer_done = 0;
-- 
2.43.0

Re: [PATCH 5.10.y v1] ALSA: usb-audio: Evaluate packsize caps at the right place

[Sasha Levin]

> diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
> @@ -953,6 +953,13 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
> +	subs->data_endpoint->packsize[0] = min(
> +		subs->data_endpoint->packsize[0],
> +		subs->data_endpoint->maxframesize);

Moving the cap into snd_usb_pcm_prepare() is the right call for 5.10 - that
tree never computes ep->maxframesize inside snd_usb_endpoint_set_params(), so
there is nowhere in that function to move it to - but nothing in the changelog
says that. Please send a v2 that spells the relocation out in the commit
message, since the diff no longer matches upstream.

Two other things before I can take it:

- The Signed-off-by needs your real name; a handle does not satisfy the DCO.
- An ack from Takashi on the 5.10 placement, he's already on Cc.

-- 
Thanks,
Sasha