Extcon: support mutually exclusive relation between cables.

There could be cables that t recannot be attaches simulatenously. Extcon
device drivers may express such information via mutually_exclusive in
struct extcon_dev.

For example, for an extcon device with 16 cables (bits 0 to 15 are
available), if mutually_exclusive = { 0x7, 0xC0, 0x81, 0 }, then, the
following attachments are prohibitted.
{0, 1}
{0, 2}
{1, 2}
{6, 7}
{0, 7}
and every attachment set that are superset of one of the above.
For the detail, please refer to linux/include/linux/extcon.h.

The concept is suggested by NeilBrown <neilb@suse.de>

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

--
Changes from V5:
- Updated sysfs format
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 22 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-extcon b/Documentation/ABI/testing/sysfs-class-extcon
index 19b18e986a57..20ab361bd8c6 100644
--- a/Documentation/ABI/testing/sysfs-class-extcon
+++ b/Documentation/ABI/testing/sysfs-class-extcon
@@ -15,6 +15,10 @@ Description:
                 may have both HDMI and Charger attached, or analog audio,
                 video, and USB cables attached simulteneously.
 
+                If there are cables mutually exclusive with each other,
+                such binary relations may be expressed with extcon_dev's
+                mutually_exclusive array.
+
 What:           /sys/class/extcon/.../name
 Date:           February 2012
 Contact:        MyungJoo Ham <myungjoo.ham@samsung.com>
@@ -73,3 +77,21 @@ Description:
                 state of cable "x" (integer between 0 and 31) of an extcon
                 device. The state value is either 0 (detached) or 1
                 (attached).
+
+What:           /sys/class/extcon/.../mutually_exclusive/...
+Date:           December 2011
+Contact:        MyungJoo Ham <myungjoo.ham@samsung.com>
+Description:
+                Shows the relations of mutually exclusiveness. For example,
+                if the mutually_exclusive array of extcon_dev is
+                {0x3, 0x5, 0xC, 0x0}, the, the output is:
+                # ls mutually_exclusive/
+                0x3
+                0x5
+                0xc
+                #
+
+                Note that mutually_exclusive is a sub-directory of the extcon
+                device and the file names under the mutually_exclusive
+                directory show the mutually-exclusive sets, not the contents
+                of the files.