SOC ID Framework


The driver-model SOC ID framework is able to provide identification information about a specific SoC in use at runtime, and also provide matching from a set of identification information from an array. This can be useful for enabling small quirks in drivers that exist between SoC variants that are impractical to implement using device tree flags. It is based on UCLASS_SOC.

  • drivers/soc/soc-uclass.c

  • include/soc.h

  • CONFIG_SOC_DEVICE is selected by drivers as needed.

Implementing a UCLASS_SOC provider

The purpose of this framework is to allow UCLASS_SOC provider drivers to supply identification information about the SoC in use at runtime. The framework allows drivers to define soc_ops that return identification strings. All soc_ops need not be defined and can be left as NULL, in which case the framework will return -ENOSYS and not consider the value when doing an soc_device_match.

It is left to the driver implementor to decide how the information returned is determined, but in general the same SOC should always return the same set of identifying information. Information returned must be in the form of a NULL terminated string.

See include/soc.h for documentation of the available soc_ops and the intended meaning of the values that can be returned. See drivers/soc/soc_sandbox.c for an example UCLASS_SOC provider driver.

Using a UCLASS_SOC driver

The framework provides the ability to retrieve and use the identification strings directly. It also has the ability to return a match from a list of different sets of SoC data using soc_device_match.

An array of ‘struct soc_attr’ can be defined, each containing ID information for a specific SoC, and when passed to soc_device_match, the identifier values for each entry in the list will be compared against the values provided by the UCLASS_SOC driver that is in use. The first entry in the list that matches all non-null values will be returned by soc_device_match.

An example of various uses of the framework can be found at test/dm/soc.c.

Describing the device using device tree

chipid: chipid {
     compatible = "sandbox,soc";

All that is required in a DT node is a compatible for a corresponding UCLASS_SOC driver.