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Create a new library for code that is used by multiple Cirrus Logic amps. This initially implements extracting amp calibration data from EFI and writing it to firmware controls. During factory calibration of built-in speakers the firmware calibration constants are stored in an EFI file. The file contains an array of calibration constants for each of the speakers. cs_amp_get_calibration_data() searches for an entry matching the requested UID stamp, otherwise by array index. If the data is found in EFI the constants for that speaker are copied back to the caller. If EFI is not enabled, the cs_amp_get_calibration_data() implementation will compile to simply return -ENOENT and the linker can drop the code. The code to write calibration controls uses cs_dsp. Building of cs_dsp is not forced. Instead, the code will compile away the calls to cs_dsp if cs_dsp is not reachable. This strategy of conditional code allows cs-amp-lib to be shared by multiple drivers without forcing inclusion of other modules that might be unnecessary. The calls to efi.get_variable() and cs_dsp are in small wrapper functions. This is so that a KUNIT_STATIC_STUB_REDIRECT can be added in a future patch to redirect these calls to replacement functions for KUnit testing. Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com> Link: https://lore.kernel.org/r/20240223153910.2063698-3-rf@opensource.cirrus.com Signed-off-by: Mark Brown <broonie@kernel.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.