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 <cw00.choi@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

--
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 <gregkh@linuxfoundation.org>

1 files changed, 185 insertions, 0 deletions

diff --git a/include/linux/extcon.h b/include/linux/extcon.h
index c9c9afe12b47..20e24b32a17d 100644
--- a/include/linux/extcon.h
+++ b/include/linux/extcon.h
@@ -24,10 +24,60 @@
 #define __LINUX_EXTCON_H__
 
 #include <linux/notifier.h>
+
+#define SUPPORTED_CABLE_MAX     32
+#define CABLE_NAME_MAX          30
+
+/*
+ * The standard cable name is to help support general notifier
+ * and notifee device drivers to share the common names.
+ * Please use standard cable names unless your notifier device has
+ * a very unique and abnormal cable or
+ * the cable type is supposed to be used with only one unique
+ * pair of notifier/notifee devices.
+ *
+ * Please add any other "standard" cables used with extcon dev.
+ *
+ * You may add a dot and number to specify version or specification
+ * of the specific cable if it is required. (e.g., "Fast-charger.18"
+ * and "Fast-charger.10" for 1.8A and 1.0A chargers)
+ * However, the notifee and notifier should be able to handle such
+ * string and if the notifee can negotiate the protocol or idenify,
+ * you don't need such convention. This convention is helpful when
+ * notifier can distinguish but notifiee cannot.
+ */
+enum extcon_cable_name {
+        EXTCON_USB = 0,
+        EXTCON_USB_HOST,
+        EXTCON_TA, /* Travel Adaptor */
+        EXTCON_FAST_CHARGER,
+        EXTCON_SLOW_CHARGER,
+        EXTCON_CHARGE_DOWNSTREAM, /* Charging an external device */
+        EXTCON_HDMI,
+        EXTCON_MHL,
+        EXTCON_DVI,
+        EXTCON_VGA,
+        EXTCON_DOCK,
+        EXTCON_LINE_IN,
+        EXTCON_LINE_OUT,
+        EXTCON_MIC_IN,
+        EXTCON_HEADPHONE_OUT,
+        EXTCON_SPDIF_IN,
+        EXTCON_SPDIF_OUT,
+        EXTCON_VIDEO_IN,
+        EXTCON_VIDEO_OUT,
+};
+extern const char *extcon_cable_name[];
+
+struct extcon_cable;
+
 /**
  * struct extcon_dev - An extcon device represents one external connector.
  * @name        The name of this extcon device. Parent device name is used
  *              if NULL.
+ * @supported_cable     Array of supported cable name ending with NULL.
+ *                      If supported_cable is NULL, cable name related APIs
+ *                      are disabled.
  * @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
@@ -38,6 +88,11 @@
  * @nh  Notifier for the state change events from this extcon
  * @entry       To support list of extcon devices so that uses can search
  *              for extcon devices based on the extcon name.
+ * @lock
+ * @max_supported       Internal value to store the number of cables.
+ * @extcon_dev_type     Device_type struct to provide attribute_groups
+ *                      customized for each extcon device.
+ * @cables      Sysfs subdirectories. Each represents one cable.
  *
  * In most cases, users only need to provide "User initializing data" of
  * this struct when registering an extcon. In some exceptional cases,
@@ -47,6 +102,7 @@
 struct extcon_dev {
         /* --- Optional user initializing data --- */
         const char      *name;
+        const char **supported_cable;
 
         /* --- Optional callbacks to override class functions --- */
         ssize_t (*print_name)(struct extcon_dev *edev, char *buf);
@@ -57,6 +113,49 @@ struct extcon_dev {
         u32             state;
         struct raw_notifier_head nh;
         struct list_head entry;
+        spinlock_t lock; /* could be called by irq handler */
+        int max_supported;
+
+        /* /sys/class/extcon/.../cable.n/... */
+        struct device_type extcon_dev_type;
+        struct extcon_cable *cables;
+};
+
+/**
+ * struct extcon_cable  - An internal data for each cable of extcon device.
+ * @edev        The extcon device
+ * @cable_index Index of this cable in the edev
+ * @attr_g      Attribute group for the cable
+ * @attr_name   "name" sysfs entry
+ * @attr_state  "state" sysfs entry
+ * @attrs       Array pointing to attr_name and attr_state for attr_g
+ */
+struct extcon_cable {
+        struct extcon_dev *edev;
+        int cable_index;
+
+        struct attribute_group attr_g;
+        struct device_attribute attr_name;
+        struct device_attribute attr_state;
+
+        struct attribute *attrs[3]; /* to be fed to attr_g.attrs */
+};
+
+/**
+ * struct extcon_specific_cable_nb - An internal data for
+ *                              extcon_register_interest().
+ * @internal_nb a notifier block bridging extcon notifier and cable notifier.
+ * @user_nb     user provided notifier block for events from a specific cable.
+ * @cable_index the target cable.
+ * @edev        the target extcon device.
+ * @previous_value      the saved previous event value.
+ */
+struct extcon_specific_cable_nb {
+        struct notifier_block internal_nb;
+        struct notifier_block *user_nb;
+        int cable_index;
+        struct extcon_dev *edev;
+        unsigned long previous_value;
 };
 
 #if IS_ENABLED(CONFIG_EXTCON)
@@ -69,16 +168,54 @@ extern int extcon_dev_register(struct extcon_dev *edev, struct device *dev);
 extern void extcon_dev_unregister(struct extcon_dev *edev);
 extern struct extcon_dev *extcon_get_extcon_dev(const char *extcon_name);
 
+/*
+ * get/set/update_state access the 32b encoded state value, which represents
+ * states of all possible cables of the multistate port. For example, if one
+ * calls extcon_set_state(edev, 0x7), it may mean that all the three cables
+ * are attached to the port.
+ */
 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);
+
+/*
+ * get/set_cable_state access each bit of the 32b encoded state value.
+ * They are used to access the status of each cable based on the cable_name
+ * or cable_index, which is retrived by extcon_find_cable_index
+ */
+extern int extcon_find_cable_index(struct extcon_dev *sdev,
+                                   const char *cable_name);
+extern int extcon_get_cable_state_(struct extcon_dev *edev, int cable_index);
+extern int extcon_set_cable_state_(struct extcon_dev *edev, int cable_index,
+                                   bool cable_state);
+
+extern int extcon_get_cable_state(struct extcon_dev *edev,
+                                  const char *cable_name);
+extern int extcon_set_cable_state(struct extcon_dev *edev,
+                                  const char *cable_name, bool cable_state);
+
+/*
+ * Following APIs are for notifiees (those who want to be notified)
+ * to register a callback for events from a specific cable of the extcon.
+ * Notifiees are the connected device drivers wanting to get notified by
+ * a specific external port of a connection device.
+ */
+extern int extcon_register_interest(struct extcon_specific_cable_nb *obj,
+                                    const char *extcon_name,
+                                    const char *cable_name,
+                                    struct notifier_block *nb);
+extern int extcon_unregister_interest(struct extcon_specific_cable_nb *nb);
 
 /*
  * Following APIs are to monitor every action of a notifier.
  * Registerer gets notified for every external port of a connection device.
+ * Probably this could be used to debug an action of notifier; however,
+ * we do not recommend to use this at normal 'notifiee' device drivers who
+ * want to be notified by a specific external port of the notifier.
  */
 extern int extcon_register_notifier(struct extcon_dev *edev,
                                     struct notifier_block *nb);
@@ -99,6 +236,41 @@ static inline u32 extcon_get_state(struct extcon_dev *edev)
 }
 
 static inline void extcon_set_state(struct extcon_dev *edev, u32 state) { }
+
+static inline void extcon_update_state(struct extcon_dev *edev, u32 mask,
+                                       u32 state)
+{ }
+
+static inline int extcon_find_cable_index(struct extcon_dev *edev,
+                                          const char *cable_name)
+{
+        return 0;
+}
+
+static inline int extcon_get_cable_state_(struct extcon_dev *edev,
+                                          int cable_index)
+{
+        return 0;
+}
+
+static inline int extcon_set_cable_state_(struct extcon_dev *edev,
+                                          int cable_index, bool cable_state)
+{
+        return 0;
+}
+
+static inline int extcon_get_cable_state(struct extcon_dev *edev,
+                        const char *cable_name)
+{
+        return 0;
+}
+
+static inline int extcon_set_cable_state(struct extcon_dev *edev,
+                        const char *cable_name, int state)
+{
+        return 0;
+}
+
 static inline struct extcon_dev *extcon_get_extcon_dev(const char *extcon_name)
 {
         return NULL;
@@ -116,5 +288,18 @@ static inline int extcon_unregister_notifier(struct extcon_dev *edev,
         return 0;
 }
 
+static inline int extcon_register_interest(struct extcon_specific_cable_nb *obj,
+                                           const char *extcon_name,
+                                           const char *cable_name,
+                                           struct notifier_block *nb)
+{
+        return 0;
+}
+
+static inline int extcon_unregister_interest(struct extcon_specific_cable_nb
+                                                    *obj)
+{
+        return 0;
+}
 #endif /* CONFIG_EXTCON */
 #endif /* __LINUX_EXTCON_H__ */