usb: phy: Dual role sysfs class definition

This CL adds a new class to monitor and change
dual role usb ports from userspace. The usb
phy drivers can register to the dual_role_usb
class and expose the capabilities of the ports.
The phy drivers can decide on whether a specific
attribute can be changed from userspace by
choosing to implement the appropriate callback.

Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
Bug: 21615151
Change-Id: I121b4a94437972b5abe8f781e3007efa8531978

1 files changed, 71 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-dual-role-usb b/Documentation/ABI/testing/sysfs-class-dual-role-usb
new file mode 100644
index 00000000000..a900fd75430
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-dual-role-usb
@@ -0,0 +1,71 @@
+What:		/sys/class/dual_role_usb/.../
+Date:		June 2015
+Contact:	Badhri Jagan Sridharan<badhri@google.com>
+Description:
+		Provide a generic interface to monitor and change
+		the state of dual role usb ports. The name here
+		refers to the name mentioned in the
+		dual_role_phy_desc that is passed while registering
+		the dual_role_phy_intstance through
+		devm_dual_role_instance_register.
+
+What:           /sys/class/dual_role_usb/.../supported_modes
+Date:           June 2015
+Contact:        Badhri Jagan Sridharan<badhri@google.com>
+Description:
+		This is a static node, once initialized this
+		is not expected to change during runtime. "dfp"
+		refers to "downstream facing port" i.e. port can
+		only act as host. "ufp" refers to "upstream
+		facing port" i.e. port can only act as device.
+		"dfp ufp" refers to "dual role port" i.e. the port
+		can either be a host port or a device port.
+
+What:		/sys/class/dual_role_usb/.../mode
+Date:		June 2015
+Contact:	Badhri Jagan Sridharan<badhri@google.com>
+Description:
+		The mode node refers to the current mode in which the
+		port is operating. "dfp" for host ports. "ufp" for device
+		ports and "none" when cable is not connected.
+
+		On devices where the USB mode is software-controllable,
+		userspace can change the mode by writing "dfp" or "ufp".
+		On devices where the USB mode is fixed in hardware,
+		this attribute is read-only.
+
+What:		/sys/class/dual_role_usb/.../power_role
+Date:		June 2015
+Contact:	Badhri Jagan Sridharan<badhri@google.com>
+Description:
+		The power_role node mentions whether the port
+		is "sink"ing or "source"ing power. "none" if
+		they are not connected.
+
+		On devices implementing USB Power Delivery,
+		userspace can control the power role by writing "sink" or
+		"source". On devices without USB-PD, this attribute is
+		read-only.
+
+What:		/sys/class/dual_role_usb/.../data_role
+Date:		June 2015
+Contact:	Badhri Jagan Sridharan<badhri@google.com>
+Description:
+		The data_role node mentions whether the port
+		is acting as "host" or "device" for USB data connection.
+		"none" if there is no active data link.
+
+		On devices implementing USB Power Delivery, userspace
+		can control the data role by writing "host" or "device".
+		On devices without USB-PD, this attribute is read-only
+
+What:		/sys/class/dual_role_usb/.../powers_vconn
+Date:		June 2015
+Contact:	Badhri Jagan Sridharan<badhri@google.com>
+Description:
+		The powers_vconn node mentions whether the port
+		is supplying power for VCONN pin.
+
+		On devices with software control of VCONN,
+		userspace can disable the power supply to VCONN by writing "n",
+		or enable the power supply by writing "y".