soc: apple: Add DockChannel driver

This patch adds a driver for Apple's DockChannel
protocol which is a hardware FIFO found on Apple
Silicon devices. Notably, it used to enable
communication with the internal trackpad and keyboard
on MacBooks with an M2 and later chipset.

Co-developed-by: Hector Martin <[email protected]>
Signed-off-by: Hector Martin <[email protected]>
Signed-off-by: Michael Reeves <[email protected]>

Author: IntegralPilot

drivers/soc/apple/Kconfig

@@ -4,6 +4,17 @@ if ARCH_APPLE || COMPILE_TEST
 
 menu "Apple SoC drivers"
 
+config APPLE_DOCKCHANNEL
+	tristate "Apple DockChannel FIFO"
+	depends on ARCH_APPLE || COMPILE_TEST
+	help
+	  DockChannel is a hardware FIFO used on Apple Silicon SoCs for
+	  communication between the application processor and various
+	  coprocessors. It is the primary transport for the internal
+	  keyboard and trackpad on M2 and later MacBook models.
+
+	  Say Y here if you have an M2 or later Apple MacBook.
+
 config APPLE_MAILBOX
 	tristate "Apple SoC mailboxes"
 	depends on PM

drivers/soc/apple/Makefile

@@ -1,5 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
+obj-$(CONFIG_APPLE_DOCKCHANNEL) += apple-dockchannel.o
+apple-dockchannel-y = dockchannel.o
+
 obj-$(CONFIG_APPLE_MAILBOX) += apple-mailbox.o
 apple-mailbox-y = mailbox.o