platform/x86: dell-smbios: Introduce dispatcher for SMM calls

This splits up the dell-smbios driver into two drivers:
* dell-smbios
* dell-smbios-smm

dell-smbios can operate with multiple different dispatcher drivers to
perform SMBIOS operations.

Also modify the interface that dell-laptop and dell-wmi use align to this
model more closely.  Rather than a single global buffer being allocated
for all drivers, each driver will allocate and be responsible for it's own
buffer. The pointer will be passed to the calling function and each
dispatcher driver will then internally copy it to the proper location to
perform it's call.

Add defines for calls used by these methods in the dell-smbios.h header
for tracking purposes.

Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
Reviewed-by: Edward O'Callaghan <quasisec@google.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>

MAINTAINERS

@@ -3985,6 +3985,12 @@ L:	platform-driver-x86@vger.kernel.org
 S:	Maintained
 F:	drivers/platform/x86/dell-smbios.*
 
+DELL SMBIOS SMM DRIVER
+M:	Mario Limonciello <mario.limonciello@dell.com>
+L:	platform-driver-x86@vger.kernel.org
+S:	Maintained
+F:	drivers/platform/x86/dell-smbios-smm.c
+
 DELL LAPTOP DRIVER
 M:	Matthew Garrett <mjg59@srcf.ucam.org>
 M:	Pali Rohár <pali.rohar@gmail.com>

drivers/platform/x86/Kconfig

@@ -93,12 +93,19 @@ config ASUS_LAPTOP
 
 config DELL_SMBIOS
 	tristate
-	select DCDBAS
+
+config DELL_SMBIOS_SMM
+	tristate "Dell SMBIOS calling interface (SMM implementation)"
+	depends on DCDBAS
+	default DCDBAS
+	select DELL_SMBIOS
 	---help---
-	This module provides common functions for kernel modules using
-	Dell SMBIOS.
+	This provides an implementation for the Dell SMBIOS calling interface
+	communicated over SMI/SMM.
 
-	If you have a Dell laptop, say Y or M here.
+	If you have a Dell computer from <=2017 you should say Y or M here.
+	If you aren't sure and this module doesn't work for your computer
+	it just won't load.
 
 config DELL_LAPTOP
 	tristate "Dell Laptop Extras"

drivers/platform/x86/Makefile

@@ -12,6 +12,7 @@ obj-$(CONFIG_MSI_LAPTOP)	+= msi-laptop.o
 obj-$(CONFIG_ACPI_CMPC)		+= classmate-laptop.o
 obj-$(CONFIG_COMPAL_LAPTOP)	+= compal-laptop.o
 obj-$(CONFIG_DELL_SMBIOS)	+= dell-smbios.o
+obj-$(CONFIG_DELL_SMBIOS_SMM)	+= dell-smbios-smm.o
 obj-$(CONFIG_DELL_LAPTOP)	+= dell-laptop.o
 obj-$(CONFIG_DELL_WMI)		+= dell-wmi.o
 obj-$(CONFIG_DELL_WMI_DESCRIPTOR)	+= dell-wmi-descriptor.o