Chapter 2: Leveraging the Regmap API and Simplifying the Code
This chapter introduces the Linux kernel register mapping abstraction layer and shows how to simplify and delegate I/O operations to the regmap subsystem. Dealing with devices, whether they are built-in in the SoC (memory mapped I/O, also known as MMIO) or seated on I2C/SPI buses, consists of accessing (reading/modifying/updating) registers. Regmap became necessary because a lot of device drivers open-coded their register access routines. Regmap stands for Register Map. It was primarily developed for ALSA SoC (ASoC) in order to get rid of redundant open-coded SPI/I2C register access routines in codec drivers. At its origin, regmap provided a set of APIs for reading/writing non-memory-map ...
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