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commit 98c27add5d96485db731a92dac31567b0486cae8 upstream. In the implicit feedback mode, some parameters are tied between both playback and capture streams. One of the tied parameters is the period size, and this can be a problem if the device has different number of channels to both streams. Assume that an application opens a playback stream that has an implicit feedback from a capture stream, and it allocates up to the max period and buffer size as much as possible. When the capture device supports only more channels than the playback, the minimum period and buffer sizes become larger than the sizes the playback stream took. That is, the minimum size will be over the max size the driver limits, and PCM core sees as if no available configuration is found, returning -EINVAL mercilessly. For avoiding this problem, we have to look through the counter part of audioformat list for each sync ep, and checks the channels. If more channels are found there, we reduce the max period and buffer sizes accordingly. You may wonder that the patch adds only the evaluation of channels between streams, and what about other parameters? Both the format and the rate are tied in the implicit fb mode, hence they are always identical. BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=215792 Fixes: 5a6c3e11c9c9 ("ALSA: usb-audio: Add hw constraint for implicit fb sync") Cc: <stable@vger.kernel.org> Link: https://lore.kernel.org/r/20220407211657.15087-1-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.