EDAC: Add a Error Check Scrub control feature

Add an Error Check Scrub (ECS) control to manage a memory device's ECS
feature.

The ECS is a feature defined in JEDEC DDR5 SDRAM Specification (JESD79-

EDAC: Add a Error Check Scrub control feature

Add an Error Check Scrub (ECS) control to manage a memory device's ECS
feature.

The ECS is a feature defined in JEDEC DDR5 SDRAM Specification (JESD79-5) and
allows the DRAM to internally read, correct single-bit errors, and write back
corrected data bits to the DRAM array while providing transparency to error
counts.

The DDR5 device contains a number of memory media Field Replaceable Units
(FRU) per device. The DDR5 ECS feature and thus the ECS control driver
supports configuring the ECS parameters per FRU.

Memory devices support the ECS feature register with the EDAC device driver,
which retrieves the ECS descriptor from the EDAC ECS driver. This driver
exposes sysfs ECS control attributes to userspace via

/sys/bus/edac/devices/<dev-name>/ecs_fruX/.

The common sysfs ECS control interface abstracts the control of an arbitrary
ECS functionality to a common set of functions.

Support for the ECS feature is added separately because the control attributes
of the DDR5 ECS feature differ from those of the scrub feature.

The sysfs ECS attribute nodes are only present if the client driver has
implemented the corresponding attribute callback function and passed the
necessary operations to the EDAC RAS feature driver during registration.

[ bp: Massage, fixup edac_dev_register() retvals. ]

Co-developed-by: Jonathan Cameron <[email protected]>
Signed-off-by: Jonathan Cameron <[email protected]>
Signed-off-by: Shiju Jose <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Reviewed-by: Fan Ni <[email protected]>
Tested-by: Fan Ni <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

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