Input: gpio-keys - add support for disabling gpios through sysfs

Now gpio-keys input driver exports 4 new attributes to userland through
sysfs:
	/sys/devices/platform/gpio-keys/keys [ro]
	/sys/devices/platform/gpio-keys/switches [ro]
	/sys/devices/platform/gpio-keys/disabled_keys [rw]
	/sys/devices/platform/gpio-keys/disables_switches [rw]

With these attributes, userland program can read which keys and
switches can be disabled and then disable/enable them as needed.
Keys and switches are exported as stringified bitmap of codes
(keycodes or switch codes). For example keys 15, 89, 100, 101,
102 are exported as: '15,89,100-102'.

Description of the attributes:
	keys - bitmap of keys which can be disabled
	switches - bitmap of switches which can be disabled
	disabled_keys - bitmap of currently disabled keys
			(bit 1 means disabled, 0 enabled)
	disabled_switches - bitmap of currently disabled switches
			(bit 1 means disabled, 0 enabled)
Signed-off-by: NMika Westerberg <ext-mika.1.westerberg@nokia.com>
Signed-off-by: NDmitry Torokhov <dtor@mail.ru>

drivers/input/keyboard/gpio_keys.c

@@ -30,13 +30,289 @@ struct gpio_button_data {
 	struct input_dev *input;
 	struct timer_list timer;
 	struct work_struct work;
+	bool disabled;
 };
 
 struct gpio_keys_drvdata {
 	struct input_dev *input;
+	struct mutex disable_lock;
+	unsigned int n_buttons;
 	struct gpio_button_data data[0];
 };
 
+/*
+ * SYSFS interface for enabling/disabling keys and switches:
+ *
+ * There are 4 attributes under /sys/devices/platform/gpio-keys/
+ *	keys [ro]              - bitmap of keys (EV_KEY) which can be
+ *	                         disabled
+ *	switches [ro]          - bitmap of switches (EV_SW) which can be
+ *	                         disabled
+ *	disabled_keys [rw]     - bitmap of keys currently disabled
+ *	disabled_switches [rw] - bitmap of switches currently disabled
+ *
+ * Userland can change these values and hence disable event generation
+ * for each key (or switch). Disabling a key means its interrupt line
+ * is disabled.
+ *
+ * For example, if we have following switches set up as gpio-keys:
+ *	SW_DOCK = 5
+ *	SW_CAMERA_LENS_COVER = 9
+ *	SW_KEYPAD_SLIDE = 10
+ *	SW_FRONT_PROXIMITY = 11
+ * This is read from switches:
+ *	11-9,5
+ * Next we want to disable proximity (11) and dock (5), we write:
+ *	11,5
+ * to file disabled_switches. Now proximity and dock IRQs are disabled.
+ * This can be verified by reading the file disabled_switches:
+ *	11,5
+ * If we now want to enable proximity (11) switch we write:
+ *	5
+ * to disabled_switches.
+ *
+ * We can disable only those keys which don't allow sharing the irq.
+ */
+
+/**
+ * get_n_events_by_type() - returns maximum number of events per @type
+ * @type: type of button (%EV_KEY, %EV_SW)
+ *
+ * Return value of this function can be used to allocate bitmap
+ * large enough to hold all bits for given type.
+ */
+static inline int get_n_events_by_type(int type)
+{
+	BUG_ON(type != EV_SW && type != EV_KEY);
+
+	return (type == EV_KEY) ? KEY_CNT : SW_CNT;
+}
+
+/**
+ * gpio_keys_disable_button() - disables given GPIO button
+ * @bdata: button data for button to be disabled
+ *
+ * Disables button pointed by @bdata. This is done by masking
+ * IRQ line. After this function is called, button won't generate
+ * input events anymore. Note that one can only disable buttons
+ * that don't share IRQs.
+ *
+ * Make sure that @bdata->disable_lock is locked when entering
+ * this function to avoid races when concurrent threads are
+ * disabling buttons at the same time.
+ */
+static void gpio_keys_disable_button(struct gpio_button_data *bdata)
+{
+	if (!bdata->disabled) {
+		/*
+		 * Disable IRQ and possible debouncing timer.
+		 */
+		disable_irq(gpio_to_irq(bdata->button->gpio));
+		if (bdata->button->debounce_interval)
+			del_timer_sync(&bdata->timer);
+
+		bdata->disabled = true;
+	}
+}
+
+/**
+ * gpio_keys_enable_button() - enables given GPIO button
+ * @bdata: button data for button to be disabled
+ *
+ * Enables given button pointed by @bdata.
+ *
+ * Make sure that @bdata->disable_lock is locked when entering
+ * this function to avoid races with concurrent threads trying
+ * to enable the same button at the same time.
+ */
+static void gpio_keys_enable_button(struct gpio_button_data *bdata)
+{
+	if (bdata->disabled) {
+		enable_irq(gpio_to_irq(bdata->button->gpio));
+		bdata->disabled = false;
+	}
+}
+
+/**
+ * gpio_keys_attr_show_helper() - fill in stringified bitmap of buttons
+ * @ddata: pointer to drvdata
+ * @buf: buffer where stringified bitmap is written
+ * @type: button type (%EV_KEY, %EV_SW)
+ * @only_disabled: does caller want only those buttons that are
+ *                 currently disabled or all buttons that can be
+ *                 disabled
+ *
+ * This function writes buttons that can be disabled to @buf. If
+ * @only_disabled is true, then @buf contains only those buttons
+ * that are currently disabled. Returns 0 on success or negative
+ * errno on failure.
+ */
+static ssize_t gpio_keys_attr_show_helper(struct gpio_keys_drvdata *ddata,
+					  char *buf, unsigned int type,
+					  bool only_disabled)
+{
+	int n_events = get_n_events_by_type(type);
+	unsigned long *bits;
+	ssize_t ret;
+	int i;
+
+	bits = kcalloc(BITS_TO_LONGS(n_events), sizeof(*bits), GFP_KERNEL);
+	if (!bits)
+		return -ENOMEM;
+
+	for (i = 0; i < ddata->n_buttons; i++) {
+		struct gpio_button_data *bdata = &ddata->data[i];
+
+		if (bdata->button->type != type)
+			continue;
+
+		if (only_disabled && !bdata->disabled)
+			continue;
+
+		__set_bit(bdata->button->code, bits);
+	}
+
+	ret = bitmap_scnlistprintf(buf, PAGE_SIZE - 2, bits, n_events);
+	buf[ret++] = '\n';
+	buf[ret] = '\0';
+
+	kfree(bits);
+
+	return ret;
+}
+
+/**
+ * gpio_keys_attr_store_helper() - enable/disable buttons based on given bitmap
+ * @ddata: pointer to drvdata
+ * @buf: buffer from userspace that contains stringified bitmap
+ * @type: button type (%EV_KEY, %EV_SW)
+ *
+ * This function parses stringified bitmap from @buf and disables/enables
+ * GPIO buttons accordinly. Returns 0 on success and negative error
+ * on failure.
+ */
+static ssize_t gpio_keys_attr_store_helper(struct gpio_keys_drvdata *ddata,
+					   const char *buf, unsigned int type)
+{
+	int n_events = get_n_events_by_type(type);
+	unsigned long *bits;
+	ssize_t error;
+	int i;
+
+	bits = kcalloc(BITS_TO_LONGS(n_events), sizeof(*bits), GFP_KERNEL);
+	if (!bits)
+		return -ENOMEM;
+
+	error = bitmap_parselist(buf, bits, n_events);
+	if (error)
+		goto out;
+
+	/* First validate */
+	for (i = 0; i < ddata->n_buttons; i++) {
+		struct gpio_button_data *bdata = &ddata->data[i];
+
+		if (bdata->button->type != type)
+			continue;
+
+		if (test_bit(bdata->button->code, bits) &&
+		    !bdata->button->can_disable) {
+			error = -EINVAL;
+			goto out;
+		}
+	}
+
+	mutex_lock(&ddata->disable_lock);
+
+	for (i = 0; i < ddata->n_buttons; i++) {
+		struct gpio_button_data *bdata = &ddata->data[i];
+
+		if (bdata->button->type != type)
+			continue;
+
+		if (test_bit(bdata->button->code, bits))
+			gpio_keys_disable_button(bdata);
+		else
+			gpio_keys_enable_button(bdata);
+	}
+
+	mutex_unlock(&ddata->disable_lock);
+
+out:
+	kfree(bits);
+	return error;
+}
+
+#define ATTR_SHOW_FN(name, type, only_disabled)				\
+static ssize_t gpio_keys_show_##name(struct device *dev,		\
+				     struct device_attribute *attr,	\
+				     char *buf)				\
+{									\
+	struct platform_device *pdev = to_platform_device(dev);		\
+	struct gpio_keys_drvdata *ddata = platform_get_drvdata(pdev);	\
+									\
+	return gpio_keys_attr_show_helper(ddata, buf,			\
+					  type, only_disabled);		\
+}
+
+ATTR_SHOW_FN(keys, EV_KEY, false);
+ATTR_SHOW_FN(switches, EV_SW, false);
+ATTR_SHOW_FN(disabled_keys, EV_KEY, true);
+ATTR_SHOW_FN(disabled_switches, EV_SW, true);
+
+/*
+ * ATTRIBUTES:
+ *
+ * /sys/devices/platform/gpio-keys/keys [ro]
+ * /sys/devices/platform/gpio-keys/switches [ro]
+ */
+static DEVICE_ATTR(keys, S_IRUGO, gpio_keys_show_keys, NULL);
+static DEVICE_ATTR(switches, S_IRUGO, gpio_keys_show_switches, NULL);
+
+#define ATTR_STORE_FN(name, type)					\
+static ssize_t gpio_keys_store_##name(struct device *dev,		\
+				      struct device_attribute *attr,	\
+				      const char *buf,			\
+				      size_t count)			\
+{									\
+	struct platform_device *pdev = to_platform_device(dev);		\
+	struct gpio_keys_drvdata *ddata = platform_get_drvdata(pdev);	\
+	ssize_t error;							\
+									\
+	error = gpio_keys_attr_store_helper(ddata, buf, type);		\
+	if (error)							\
+		return error;						\
+									\
+	return count;							\
+}
+
+ATTR_STORE_FN(disabled_keys, EV_KEY);
+ATTR_STORE_FN(disabled_switches, EV_SW);
+
+/*
+ * ATTRIBUTES:
+ *
+ * /sys/devices/platform/gpio-keys/disabled_keys [rw]
+ * /sys/devices/platform/gpio-keys/disables_switches [rw]
+ */
+static DEVICE_ATTR(disabled_keys, S_IWUSR | S_IRUGO,
+		   gpio_keys_show_disabled_keys,
+		   gpio_keys_store_disabled_keys);
+static DEVICE_ATTR(disabled_switches, S_IWUSR | S_IRUGO,
+		   gpio_keys_show_disabled_switches,
+		   gpio_keys_store_disabled_switches);
+
+static struct attribute *gpio_keys_attrs[] = {
+	&dev_attr_keys.attr,
+	&dev_attr_switches.attr,
+	&dev_attr_disabled_keys.attr,
+	&dev_attr_disabled_switches.attr,
+	NULL,
+};
+
+static struct attribute_group gpio_keys_attr_group = {
+	.attrs = gpio_keys_attrs,
+};
+
 static void gpio_keys_report_event(struct gpio_button_data *bdata)
 {
 	struct gpio_keys_button *button = bdata->button;
@@ -79,11 +355,13 @@ static irqreturn_t gpio_keys_isr(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
-static int __devinit gpio_keys_setup_key(struct device *dev,
+static int __devinit gpio_keys_setup_key(struct platform_device *pdev,
 					 struct gpio_button_data *bdata,
 					 struct gpio_keys_button *button)
 {
 	char *desc = button->desc ? button->desc : "gpio_keys";
+	struct device *dev = &pdev->dev;
+	unsigned long irqflags;
 	int irq, error;
 
 	setup_timer(&bdata->timer, gpio_keys_timer, (unsigned long)bdata);
@@ -112,10 +390,15 @@ static int __devinit gpio_keys_setup_key(struct device *dev,
 		goto fail3;
 	}
 
-	error = request_irq(irq, gpio_keys_isr,
-			    IRQF_SHARED |
-			    IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
-			    desc, bdata);
+	irqflags = IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING;
+	/*
+	 * If platform has specified that the button can be disabled,
+	 * we don't want it to share the interrupt line.
+	 */
+	if (!button->can_disable)
+		irqflags |= IRQF_SHARED;
+
+	error = request_irq(irq, gpio_keys_isr, irqflags, desc, bdata);
 	if (error) {
 		dev_err(dev, "Unable to claim irq %d; error %d\n",
 			irq, error);
@@ -149,6 +432,10 @@ static int __devinit gpio_keys_probe(struct platform_device *pdev)
 		goto fail1;
 	}
 
+	ddata->input = input;
+	ddata->n_buttons = pdata->nbuttons;
+	mutex_init(&ddata->disable_lock);
+
 	platform_set_drvdata(pdev, ddata);
 
 	input->name = pdev->name;
@@ -164,8 +451,6 @@ static int __devinit gpio_keys_probe(struct platform_device *pdev)
 	if (pdata->rep)
 		__set_bit(EV_REP, input->evbit);
 
-	ddata->input = input;
-
 	for (i = 0; i < pdata->nbuttons; i++) {
 		struct gpio_keys_button *button = &pdata->buttons[i];
 		struct gpio_button_data *bdata = &ddata->data[i];
@@ -174,7 +459,7 @@ static int __devinit gpio_keys_probe(struct platform_device *pdev)
 		bdata->input = input;
 		bdata->button = button;
 
-		error = gpio_keys_setup_key(dev, bdata, button);
+		error = gpio_keys_setup_key(pdev, bdata, button);
 		if (error)
 			goto fail2;
 
@@ -184,13 +469,20 @@ static int __devinit gpio_keys_probe(struct platform_device *pdev)
 		input_set_capability(input, type, button->code);
 	}
 
-	error = input_register_device(input);
+	error = sysfs_create_group(&pdev->dev.kobj, &gpio_keys_attr_group);
 	if (error) {
-		dev_err(dev, "Unable to register input device, "
-			"error: %d\n", error);
+		dev_err(dev, "Unable to export keys/switches, error: %d\n",
+			error);
 		goto fail2;
 	}
 
+	error = input_register_device(input);
+	if (error) {
+		dev_err(dev, "Unable to register input device, error: %d\n",
+			error);
+		goto fail3;
+	}
+
 	/* get current state of buttons */
 	for (i = 0; i < pdata->nbuttons; i++)
 		gpio_keys_report_event(&ddata->data[i]);
@@ -200,6 +492,8 @@ static int __devinit gpio_keys_probe(struct platform_device *pdev)
 
 	return 0;
 
+ fail3:
+	sysfs_remove_group(&pdev->dev.kobj, &gpio_keys_attr_group);
  fail2:
 	while (--i >= 0) {
 		free_irq(gpio_to_irq(pdata->buttons[i].gpio), &ddata->data[i]);
@@ -224,6 +518,8 @@ static int __devexit gpio_keys_remove(struct platform_device *pdev)
 	struct input_dev *input = ddata->input;
 	int i;
 
+	sysfs_remove_group(&pdev->dev.kobj, &gpio_keys_attr_group);
+
 	device_init_wakeup(&pdev->dev, 0);
 
 	for (i = 0; i < pdata->nbuttons; i++) {

include/linux/gpio_keys.h

@@ -10,6 +10,7 @@ struct gpio_keys_button {
 	int type;		/* input event type (EV_KEY, EV_SW) */
 	int wakeup;		/* configure the button as a wake-up source */
 	int debounce_interval;	/* debounce ticks interval in msecs */
+	bool can_disable;
 };
 
 struct gpio_keys_platform_data {