Extcon: support multiple states at a device.

One switch device (e.g., MUIC(MAX8997, MAX77686, ...), and some 30-pin
devices) may have multiple cables attached. For example, one
30-pin port may inhabit a USB cable, an HDMI cable, and a mic.
Thus, one switch device requires multiple state bits each representing
a type of cable.

For such purpose, we use the 32bit state variable; thus, up to 32
different type of cables may be defined for a switch device. The list of
possible cables is defined by the array of cable names in the switch_dev
struct given to the class.

Signed-off-by: Chanwoo Choi <[email protected]>
Signed-off-by: MyungJoo Ham <[email protected]>
Signed-off-by: Kyungmin Park <[email protected]>

--
Changes from V7
- Bugfixed in _call_per_cable() (incorrect nb) (Chanwoo Choi)
- Compiler error in header for !CONFIG_EXTCON (Chanwoo Choi)

Changes from V5
- Sysfs style reformed: subdirectory per cable.
- Updated standard cable names
- Removed unnecessary printf
- Bugfixes after testing

Changes from V4
- Bugfixes after more testing at Exynos4412 boards with userspace
  processses.

Changes from V3
- Bugfixes after more testing at Exynos4412 boards.

Changes from V2
- State can be stored by user
- Documentation updated

Changes from RFC
- Switch is renamed to extcon
- Added kerneldoc comments
- Added APIs to support "standard" cable names
- Added helper APIs to support notifier block registration with cable
  name.
- Regrouped function list in the header file.
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Documentation/ABI/testing/sysfs-class-extcon

@@ -1,14 +1,22 @@
 What:		/sys/class/extcon/.../
-Date:		December 2011
+Date:		February 2012
 Contact:	MyungJoo Ham <[email protected]>
 Description:
 		Provide a place in sysfs for the extcon objects.
 		This allows accessing extcon specific variables.
 		The name of extcon object denoted as ... is the name given
 		with extcon_dev_register.
 
+		One extcon device denotes a single external connector
+		port. An external connector may have multiple cables
+		attached simultaneously. Many of docks, cradles, and
+		accessory cables have such capability. For example,
+		the 30-pin port of Nuri board (/arch/arm/mach-exynos)
+		may have both HDMI and Charger attached, or analog audio,
+		video, and USB cables attached simulteneously.
+
 What:		/sys/class/extcon/.../name
-Date:		December 2011
+Date:		February 2012
 Contact:	MyungJoo Ham <[email protected]>
 Description:
 		The /sys/class/extcon/.../name shows the name of the extcon
@@ -17,10 +25,51 @@ Description:
 		this sysfs node.
 
 What:		/sys/class/extcon/.../state
-Date:		December 2011
+Date:		February 2012
+Contact:	MyungJoo Ham <[email protected]>
+Description:
+		The /sys/class/extcon/.../state shows and stores the cable
+		attach/detach information of the corresponding extcon object.
+		If the extcon object has an optional callback "show_state"
+		defined, the showing function is overriden with the optional
+		callback.
+
+		If the default callback for showing function is used, the
+		format is like this:
+		# cat state
+		USB_OTG=1
+		HDMI=0
+		TA=1
+		EAR_JACK=0
+		#
+		In this example, the extcon device have USB_OTG and TA
+		cables attached and HDMI and EAR_JACK cables detached.
+
+		In order to update the state of an extcon device, enter a hex
+		state number starting with 0x.
+		 echo 0xHEX > state
+
+		This updates the whole state of the extcon dev.
+		Inputs of all the methods are required to meet the
+		mutually_exclusive contidions if they exist.
+
+		It is recommended to use this "global" state interface if
+		you need to enter the value atomically. The later state
+		interface associated with each cable cannot update
+		multiple cable states of an extcon device simultaneously.
+
+What:		/sys/class/extcon/.../cable.x/name
+Date:		February 2012
+Contact:	MyungJoo Ham <[email protected]>
+Description:
+		The /sys/class/extcon/.../cable.x/name shows the name of cable
+		"x" (integer between 0 and 31) of an extcon device.
+
+What:		/sys/class/extcon/.../cable.x/state
+Date:		February 2012
 Contact:	MyungJoo Ham <[email protected]>
 Description:
-		The /sys/class/extcon/.../state shows the cable attach/detach
-		information of the corresponding extcon object. If the extcon
-		objecct has an optional callback "show_state" defined, the
-		callback will provide the name with this sysfs node.
+		The /sys/class/extcon/.../cable.x/name shows and stores the
+		state of cable "x" (integer between 0 and 31) of an extcon
+		device. The state value is either 0 (detached) or 1
+		(attached).