Chapter 12: Leveraging the NVMEM Framework

The NVMEM (Non-Volatile MEMory) framework is the kernel layer to handle non-volatile storage, such as EEPROM, eFuse, and so on. The drivers for these devices used to be stored in drivers/misc/, where most of the time each one had to implement its own API to handle identical functionalities, either for kernel users or to expose its content to user space. It turned out that these drivers seriously lacked abstraction code. Moreover, the increasing support for the number of these devices in the kernel led to a lot of code duplication.

The introduction of this framework in the kernel aims at solving these previously mentioned issues. It also introduces DT representation for consumer devices to get the data they require (MAC addresses, SoC/revision ID, part numbers, and so on) from the NVMEM. We will begin this chapter by introducing NVMEM data structures, which are mandatory to walk through the framework, and then we will look at the NVMEM provider...