b96681bd58
So far we used to read the current value of the mixer element dynamically at the first access, and the error from a GET_CUR message is treated as a fatal error (unless QUIRK_IGNORE_CTL_ERROR is set). It's rather inconvenient, as most of GET_CUR errors are no fatal, and we can continue operation with assumption of some fixed value. This patch makes the USB-audio driver to change the behavior at probe time; now it tries to initialize the current value of each mixer element that is built from a feature unit (those for typically for mixer volumes and switches). When a read failure happens, it tries to set the known minimum value. After that point, a cached value is used always, hence we won't hit GET_CUR message error any longer. The error from GET_CUR message is still shown as a warning normally, but only once at the probe time, and it'll keep operating. If the message is confirmed to be harmless, it can be shut up by QUIRK_IGNORE_CTL_ERROR quirk flag, too. Tested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Link: https://lore.kernel.org/r/20211014130636.17860-4-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.