ACPI: Introduce Platform Firmware Runtime Telemetry driver

This driver allows user space to fetch telemetry data from the
firmware with the help of the Platform Firmware Runtime Telemetry
interface.

Both PFRU and PFRT are based on ACPI _DSM interfaces located under
special device objects in the ACPI Namespace, but these interfaces
are different from each other, so it is better to provide a separate
driver from each of them, even though they share some common
definitions and naming conventions.

Tested-by: Hongyu Ning <hongyu.ning@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/Kconfig

@@ -532,8 +532,12 @@ config ACPI_PFRUT
 	  The existing firmware code can be modified (driver update) or
 	  extended by adding new code to the firmware (code injection).
 
-	  To compile this driver as module, choose M here:
-	  the module will be called pfr_update.
+	  Besides, the telemetry driver allows user space to fetch telemetry
+	  data from the firmware with the help of the Platform Firmware Runtime
+	  Telemetry interface.
+
+	  To compile the drivers as modules, choose M here:
+	  the modules will be called pfr_update and pfr_telemetry.
 
 if ARM64
 source "drivers/acpi/arm64/Kconfig"

drivers/acpi/Makefile

@@ -102,7 +102,7 @@ obj-$(CONFIG_ACPI_CPPC_LIB)	+= cppc_acpi.o
 obj-$(CONFIG_ACPI_SPCR_TABLE)	+= spcr.o
 obj-$(CONFIG_ACPI_DEBUGGER_USER) += acpi_dbg.o
 obj-$(CONFIG_ACPI_PPTT) 	+= pptt.o
-obj-$(CONFIG_ACPI_PFRUT)	+= pfr_update.o
+obj-$(CONFIG_ACPI_PFRUT)	+= pfr_update.o pfr_telemetry.o
 
 # processor has its own "processor." module_param namespace
 processor-y			:= processor_driver.o