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, 23 insertions, 5 deletions

diff --git a/include/linux/extcon.h b/include/linux/extcon.h
index 20e24b32a17d..6495f7731400 100644
--- a/include/linux/extcon.h
+++ b/include/linux/extcon.h
@@ -78,6 +78,14 @@ struct extcon_cable;
  * @supported_cable     Array of supported cable name ending with NULL.
  *                      If supported_cable is NULL, cable name related APIs
  *                      are disabled.
+ * @mutually_exclusive  Array of mutually exclusive set of cables that cannot
+ *                      be attached simultaneously. The array should be
+ *                      ending with NULL or be NULL (no mutually exclusive
+ *                      cables). For example, if it is { 0x7, 0x30, 0}, then,
+ *                      {0, 1}, {0, 1, 2}, {0, 2}, {1, 2}, or {4, 5} cannot
+ *                      be attached simulataneously. {0x7, 0} is equivalent to
+ *                      {0x3, 0x6, 0x5, 0}. If it is {0xFFFFFFFF, 0}, there
+ *                      can be no simultaneous connections.
  * @print_name  An optional callback to override the method to print the
  *              name of the extcon device.
  * @print_state An optional callback to override the method to print the
@@ -103,6 +111,7 @@ struct extcon_dev {
         /* --- Optional user initializing data --- */
         const char      *name;
         const char **supported_cable;
+        const u32       *mutually_exclusive;
 
         /* --- Optional callbacks to override class functions --- */
         ssize_t (*print_name)(struct extcon_dev *edev, char *buf);
@@ -119,6 +128,10 @@ struct extcon_dev {
         /* /sys/class/extcon/.../cable.n/... */
         struct device_type extcon_dev_type;
         struct extcon_cable *cables;
+        /* /sys/class/extcon/.../mutually_exclusive/... */
+        struct attribute_group attr_g_muex;
+        struct attribute **attrs_muex;
+        struct device_attribute *d_attrs_muex;
 };
 
 /**
@@ -179,8 +192,8 @@ static inline u32 extcon_get_state(struct extcon_dev *edev)
         return edev->state;
 }
 
-extern void extcon_set_state(struct extcon_dev *edev, u32 state);
-extern void extcon_update_state(struct extcon_dev *edev, u32 mask, u32 state);
+extern int extcon_set_state(struct extcon_dev *edev, u32 state);
+extern int extcon_update_state(struct extcon_dev *edev, u32 mask, u32 state);
 
 /*
  * get/set_cable_state access each bit of the 32b encoded state value.
@@ -235,11 +248,16 @@ static inline u32 extcon_get_state(struct extcon_dev *edev)
         return 0;
 }
 
-static inline void extcon_set_state(struct extcon_dev *edev, u32 state) { }
+static inline int extcon_set_state(struct extcon_dev *edev, u32 state)
+{
+        return 0;
+}
 
-static inline void extcon_update_state(struct extcon_dev *edev, u32 mask,
+static inline int extcon_update_state(struct extcon_dev *edev, u32 mask,
                                        u32 state)
-{ }
+{
+        return 0;
+}
 
 static inline int extcon_find_cable_index(struct extcon_dev *edev,
                                           const char *cable_name)