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Merge series from Charles Keepax <ckeepax@opensource.cirrus.com>: In some cs42l43 systems a couple of cs35l56 amplifiers are attached to the cs42l43's SPI and I2S. On Windows the cs42l43 is controlled by a SDCA class driver and these two amplifiers are controlled by firmware running on the cs42l43. However, under Linux the decision was made to interact with the cs42l43 directly, affording the user greater control over the audio system. However, this has resulted in an issue where these two bridged cs35l56 amplifiers are not populated in ACPI and must be added manually. There is at least an SDCA extension unit DT entry we can key off. The process of adding this is handled using a software node, firstly the ability to add native chip selects to software nodes must be added. Secondly, an additional flag for naming the SPI devices is added this allows the machine driver to key to the correct amplifier. Then finally, the cs42l43 SPI driver adds the two amplifiers directly onto its SPI bus. An additional series will follow soon to add the audio machine driver parts (in the sof-sdw driver), however that is fairly orthogonal to this part of the process, getting the actual amplifiers registered.
Linux kernel
============
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