usb: typec: Add driver for DisplayPort alternate mode

DisplayPort USB Type-C Alt Mode allows DisplayPort displays
and adapters to be attached to the USB Type-C ports on the
system.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Tested-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Heikki Krogerus

Documentation/ABI/testing/sysfs-driver-typec-displayport

@@ -0,0 +1,49 @@
+What:		/sys/bus/typec/devices/.../displayport/configuration
+Date:		July 2018
+Contact:	Heikki Krogerus <heikki.krogerus@linux.intel.com>
+Description:
+		Shows the current DisplayPort configuration for the connector.
+		Valid values are USB, source and sink. Source means DisplayPort
+		source, and sink means DisplayPort sink.
+
+		All supported configurations are listed as space separated list
+		with the active one wrapped in square brackets.
+
+		Source example:
+
+			USB [source] sink
+
+		The configuration can be changed by writing to the file
+
+		Note. USB configuration does not equal to Exit Mode. It is
+		separate configuration defined in VESA DisplayPort Alt Mode on
+		USB Type-C Standard. Functionally it equals to the situation
+		where the mode has been exited (to exit the mode, see
+		Documentation/ABI/testing/sysfs-bus-typec, and use file
+		/sys/bus/typec/devices/.../active).
+
+What:		/sys/bus/typec/devices/.../displayport/pin_assignment
+Date:		July 2018
+Contact:	Heikki Krogerus <heikki.krogerus@linux.intel.com>
+Description:
+		VESA DisplayPort Alt Mode on USB Type-C Standard defines six
+		different pin assignments for USB Type-C connector that are
+		labeled A, B, C, D, E, and F. The supported pin assignments are
+		listed as space separated list with the active one wrapped in
+		square brackets.
+
+		Example:
+
+			C [D]
+
+		Pin assignment can be changed by writing to the file. It is
+		possible to set pin assignment before configuration has been
+		set, but the assignment will not be active before the
+		connector is actually configured.
+
+		Note. As of VESA DisplayPort Alt Mode on USB Type-C Standard
+		version 1.0b, pin assignments A, B, and F are deprecated. Only
+		pin assignment D can now carry simultaneously one channel of
+		USB SuperSpeed protocol. From user perspective pin assignments C
+		and E are equal, where all channels on the connector are used
+		for carrying DisplayPort protocol (allowing higher resolutions).

drivers/usb/typec/Kconfig

@@ -104,4 +104,6 @@ config TYPEC_TPS6598X
 
 source "drivers/usb/typec/mux/Kconfig"
 
+source "drivers/usb/typec/altmodes/Kconfig"
+
 endif # TYPEC

drivers/usb/typec/Makefile

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_TYPEC)		+= typec.o
 typec-y				:= class.o mux.o bus.o
+obj-$(CONFIG_TYPEC)		+= altmodes/
 obj-$(CONFIG_TYPEC_TCPM)	+= tcpm.o
 obj-y				+= fusb302/
 obj-$(CONFIG_TYPEC_WCOVE)	+= typec_wcove.o

drivers/usb/typec/altmodes/Kconfig

@@ -0,0 +1,14 @@
+
+menu "USB Type-C Alternate Mode drivers"
+
+config TYPEC_DP_ALTMODE
+	tristate "DisplayPort Alternate Mode driver"
+	help
+	  DisplayPort USB Type-C Alternate Mode allows DisplayPort
+	  displays and adapters to be attached to the USB Type-C
+	  connectors on the system.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called typec_displayport.
+
+endmenu

drivers/usb/typec/altmodes/Makefile

@@ -0,0 +1,2 @@
+obj-$(CONFIG_TYPEC_DP_ALTMODE)		+= typec_displayport.o
+typec_displayport-y			:= displayport.o