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198dde085e
Under certain situations (typically in the implicit feedback mode), USB-audio driver starts a playback stream already at PCM prepare call even before the actual PCM trigger-START call. For implicit feedback mode, this effectively starts two streams for data and sync endpoints, and if a coupled sync stream gets XRUN at this point, it results in an error -EPIPE. The problem is that currently we return -EPIPE error as is from the prepare. Then application tries to recover again via the prepare call, but it'll fail again because the sync-stop is missing. The sync-stop is missing because it's an internal trigger call (hence the PCM core isn't involved). Since we'll need to re-issue the prepare in anyway when trapped into this pitfall, this patch attempts to address it in a bit different way; namely, the driver tries to prepare once again after syncing the stop manually by itself -- so applications don't see the internal error. At the second failure, we report the error as is, but this shouldn't happen in normal situations. Reported-and-tested-by: Carl Hetherington <lists@carlh.net> Cc: <stable@vger.kernel.org> Link: https://lore.kernel.org/r/b4e71631-4a94-613-27b2-fb595792630@carlh.net Link: https://lore.kernel.org/r/20221205132124.11585-4-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de>
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.