This is a note to let you know that I've just added the patch titled
ALSA: usb-audio: Allow modifying parameters with succeeding hw_params calls
to the 5.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
alsa-usb-audio-allow-modifying-parameters-with-succeeding-hw_params-calls.patch
and it can be found in the queue-5.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 5f5e6a3e8b1df52f79122e447855cffbf1710540 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@xxxxxxx>
Date: Sun, 28 Feb 2021 09:01:38 +0100
Subject: ALSA: usb-audio: Allow modifying parameters with succeeding hw_params calls
From: Takashi Iwai <tiwai@xxxxxxx>
commit 5f5e6a3e8b1df52f79122e447855cffbf1710540 upstream.
The recent fix for the hw constraints for implicit feedback streams
via commit e4ea77f8e53f ("ALSA: usb-audio: Always apply the hw
constraints for implicit fb sync") added the check of the matching
endpoints and whether those EPs are already opened. This is needed
and correct, per se, even for the normal streams without the implicit
feedback, as the endpoint setup is exclusive.
However, it's reported that there seem applications that behave in
unexpected ways to update the hw_params without clearing the previous
setup via hw_free, and those hit a problem now: then hw_params is
called with still the previous EP setup kept, hence it's restricted
with the previous own setup. Although the obvious fix is to call
snd_pcm_hw_free() API in the application side, it's a kind of
unwelcome change.
This patch tries to ease the situation: in the endpoint check, we add
a couple of more conditions and now skip the endpoint that is being
used only by the stream in question itself. That is, in addition to
the presence check of ep (ep->cur_audiofmt is non-NULL), when the
following conditions are met, we skip such an ep:
- ep->opened == 1, and
- ep->cur_audiofmt == subs->cur_audiofmt.
subs->cur_audiofmt is non-NULL only if it's a re-setup of hw_params,
and ep->cur_audiofmt points to the currently set up parameters. So if
those match, it must be this stream itself.
Fixes: e4ea77f8e53f ("ALSA: usb-audio: Always apply the hw constraints for implicit fb sync")
BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=211941
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20210228080138.9936-1-tiwai@xxxxxxx
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
sound/usb/pcm.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -845,13 +845,19 @@ get_sync_ep_from_substream(struct snd_us
list_for_each_entry(fp, &subs->fmt_list, list) {
ep = snd_usb_get_endpoint(chip, fp->endpoint);
- if (ep && ep->cur_rate)
- return ep;
+ if (ep && ep->cur_audiofmt) {
+ /* if EP is already opened solely for this substream,
+ * we still allow us to change the parameter; otherwise
+ * this substream has to follow the existing parameter
+ */
+ if (ep->cur_audiofmt != subs->cur_audiofmt || ep->opened > 1)
+ return ep;
+ }
if (!fp->implicit_fb)
continue;
/* for the implicit fb, check the sync ep as well */
ep = snd_usb_get_endpoint(chip, fp->sync_ep);
- if (ep && ep->cur_rate)
+ if (ep && ep->cur_audiofmt)
return ep;
}
return NULL;
Patches currently in stable-queue which might be from tiwai@xxxxxxx are
queue-5.11/alsa-usb-audio-allow-modifying-parameters-with-succeeding-hw_params-calls.patch
queue-5.11/alsa-usb-audio-drop-bogus-db-range-in-too-low-level.patch
queue-5.11/alsa-usb-audio-use-corsair-virtuoso-mapping-for-corsair-virtuoso-se.patch
queue-5.11/alsa-usb-audio-don-t-abort-even-if-the-clock-rate-differs.patch
queue-5.11/alsa-hda-realtek-enable-headset-mic-of-acer-swift-with-alc256.patch
