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Subject[PATCH v5 4/5] Extcon: support mutually exclusive relation between cables.
Date
There could be cables that cannot 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>
---
Documentation/ABI/testing/sysfs-class-extcon | 19 +++++++
drivers/extcon/extcon_class.c | 70 +++++++++++++++++++++++---
include/linux/extcon.h | 24 +++++++--
3 files changed, 101 insertions(+), 12 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-class-extcon b/Documentation/ABI/testing/sysfs-class-extcon
index 31bb609..5e5f9a9 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: December 2011
Contact: MyungJoo Ham <myungjoo.ham@samsung.com>
@@ -54,3 +58,18 @@ Description:
Method 1 updates the state (0 or 1) of the
corresponding cable (either the name or index of the cable).
Method 2 updates the whole state of the extcon dev.
+ Inputs of all the methods are required to meet the
+ mutually_exclusive contidions if they exist.
+
+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:
+ # cat mutually_exclusive
+ 0x3
+ 0x5
+ 0xC
+ #
diff --git a/drivers/extcon/extcon_class.c b/drivers/extcon/extcon_class.c
index 2803bd0..768b70a 100644
--- a/drivers/extcon/extcon_class.c
+++ b/drivers/extcon/extcon_class.c
@@ -56,6 +56,39 @@ struct class *extcon_class_for_android;
static LIST_HEAD(extcon_dev_list);
static DEFINE_MUTEX(extcon_dev_list_lock);

+/**
+ * check_mutually_exclusive - Check if new_state violates mutually_exclusive
+ * condition.
+ * @edev: the extcon device
+ * @new_state: new cable attach status for @edev
+ *
+ * Returns 0 if nothing violates. Returns the index + 1 for the first
+ * violated condition.
+ */
+static int check_mutually_exclusive(struct extcon_dev *edev, u32 new_state)
+{
+ int i = 0;
+
+ if (!edev->mutually_exclusive)
+ return 0;
+
+ for (i = 0; edev->mutually_exclusive[i]; i++) {
+ int count = 0, j;
+ u32 correspondants = new_state & edev->mutually_exclusive[i];
+ u32 exp = 1;
+
+ for (j = 0; j < 32; j++) {
+ if (exp & correspondants)
+ count++;
+ if (count > 1)
+ return i + 1;
+ exp <<= 1;
+ }
+ }
+
+ return 0;
+}
+
static ssize_t state_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
@@ -84,7 +117,7 @@ static ssize_t state_show(struct device *dev, struct device_attribute *attr,
return count;
}

-void extcon_set_state(struct extcon_dev *edev, u32 state);
+int extcon_set_state(struct extcon_dev *edev, u32 state);
static ssize_t state_store(struct device *dev, struct device_attribute *attr,
const char *buf, size_t count)
{
@@ -111,7 +144,7 @@ static ssize_t state_store(struct device *dev, struct device_attribute *attr,
if (ret == 0)
ret = -EINVAL;
else
- extcon_set_state(edev, state);
+ ret = extcon_set_state(edev, state);
} else {
ret = -EINVAL;
}
@@ -135,6 +168,23 @@ static ssize_t name_show(struct device *dev, struct device_attribute *attr,
return sprintf(buf, "%s\n", dev_name(edev->dev));
}

+static ssize_t mutually_exclusive_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct extcon_dev *edev = (struct extcon_dev *) dev_get_drvdata(dev);
+ int i;
+ int count = 0;
+
+ if (!edev->mutually_exclusive || !edev->mutually_exclusive[0])
+ return sprintf(buf, "No cables are mutually exclusive.\n");
+
+ for (i = 0; edev->mutually_exclusive[i]; i++)
+ count += sprintf(buf + count, "0x%x\n",
+ edev->mutually_exclusive[i]);
+
+ return count;
+}
+
/**
* extcon_update_state() - Update the cable attach states of the extcon device
* only for the masked bits.
@@ -150,7 +200,7 @@ static ssize_t name_show(struct device *dev, struct device_attribute *attr,
* Note that the notifier provides which bits are changed in the state
* variable with the val parameter (second) to the callback.
*/
-void extcon_update_state(struct extcon_dev *edev, u32 mask, u32 state)
+int extcon_update_state(struct extcon_dev *edev, u32 mask, u32 state)
{
char name_buf[120];
char state_buf[120];
@@ -165,6 +215,10 @@ void extcon_update_state(struct extcon_dev *edev, u32 mask, u32 state)
if (edev->state != ((edev->state & ~mask) | (state & mask))) {
u32 old_state = edev->state;

+ if (check_mutually_exclusive(edev, (edev->state & ~mask) |
+ (state & mask)))
+ return -EPERM;
+
edev->state &= ~mask;
edev->state |= state & mask;

@@ -206,6 +260,8 @@ void extcon_update_state(struct extcon_dev *edev, u32 mask, u32 state)
/* No changes */
spin_unlock_irqrestore(&edev->lock, flags);
}
+
+ return 0;
}
EXPORT_SYMBOL_GPL(extcon_update_state);

@@ -217,9 +273,9 @@ EXPORT_SYMBOL_GPL(extcon_update_state);
* Note that notifier provides which bits are changed in the state
* variable with the val parameter (second) to the callback.
*/
-void extcon_set_state(struct extcon_dev *edev, u32 state)
+int extcon_set_state(struct extcon_dev *edev, u32 state)
{
- extcon_update_state(edev, 0xffffffff, state);
+ return extcon_update_state(edev, 0xffffffff, state);
}
EXPORT_SYMBOL_GPL(extcon_set_state);

@@ -293,8 +349,7 @@ int extcon_set_cable_state_(struct extcon_dev *edev,
return -EINVAL;

state = cable_state ? (1 << index) : 0;
- extcon_update_state(edev, 1 << index, state);
- return 0;
+ return extcon_update_state(edev, 1 << index, state);
}
EXPORT_SYMBOL_GPL(extcon_set_cable_state_);

@@ -440,6 +495,7 @@ EXPORT_SYMBOL_GPL(extcon_unregister_notifier);
static struct device_attribute extcon_attrs[] = {
__ATTR(state, S_IRUGO | S_IWUSR, state_show, state_store),
__ATTR_RO(name),
+ __ATTR_RO(mutually_exclusive),
__ATTR_NULL,
};

diff --git a/include/linux/extcon.h b/include/linux/extcon.h
index 4384d8f..20b8e5d 100644
--- a/include/linux/extcon.h
+++ b/include/linux/extcon.h
@@ -75,6 +75,14 @@ extern const char *extcon_cable_name[];
* @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
@@ -98,6 +106,7 @@ struct extcon_dev {
const char *name;
bool use_class_name_switch;
const char **supported_cable;
+ const u32 *mutually_exclusive;

/* --- Optional callbacks to override class functions --- */
ssize_t (*print_name)(struct extcon_dev *edev, char *buf);
@@ -168,8 +177,8 @@ 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.
@@ -224,11 +233,16 @@ 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)
--
1.7.4.1


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