Input: input-polldev - add sysfs interface for controlling poll interval

Sysfs entry for reading and setting of the polling interval. If the
interval is set to 0, polling is stopped. Polling is restarted when
interval is changed to non-zero.

sysfs entries:
poll = current polling interval in msec (RW)
max = max allowed polling interval (RO)
min = min allowed polling interval (RO)

Minimum and maximum limit for interval can be set while setting up the
device.

Interval can be adjusted even if the input device is not currently open.

[dtor@mail.ru: add kernel doc markup for the new fields]
Signed-off-by: Samu Onkalo <samu.p.onkalo@nokia.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/input-polldev.c

@@ -56,21 +56,26 @@ static void input_polldev_stop_workqueue(void)
 	mutex_unlock(&polldev_mutex);
 }
 
-static void input_polled_device_work(struct work_struct *work)
+static void input_polldev_queue_work(struct input_polled_dev *dev)
 {
-	struct input_polled_dev *dev =
-		container_of(work, struct input_polled_dev, work.work);
 	unsigned long delay;
 
-	dev->poll(dev);
-
 	delay = msecs_to_jiffies(dev->poll_interval);
 	if (delay >= HZ)
 		delay = round_jiffies_relative(delay);
 
 	queue_delayed_work(polldev_wq, &dev->work, delay);
 }
 
+static void input_polled_device_work(struct work_struct *work)
+{
+	struct input_polled_dev *dev =
+		container_of(work, struct input_polled_dev, work.work);
+
+	dev->poll(dev);
+	input_polldev_queue_work(dev);
+}
+
 static int input_open_polled_device(struct input_dev *input)
 {
 	struct input_polled_dev *dev = input_get_drvdata(input);
@@ -100,6 +105,83 @@ static void input_close_polled_device(struct input_dev *input)
 		dev->close(dev);
 }
 
+/* SYSFS interface */
+
+static ssize_t input_polldev_get_poll(struct device *dev,
+				      struct device_attribute *attr, char *buf)
+{
+	struct input_polled_dev *polldev = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", polldev->poll_interval);
+}
+
+static ssize_t input_polldev_set_poll(struct device *dev,
+				struct device_attribute *attr, const char *buf,
+				size_t count)
+{
+	struct input_polled_dev *polldev = dev_get_drvdata(dev);
+	struct input_dev *input = polldev->input;
+	unsigned long interval;
+
+	if (strict_strtoul(buf, 0, &interval))
+		return -EINVAL;
+
+	if (interval < polldev->poll_interval_min)
+		return -EINVAL;
+
+	if (interval > polldev->poll_interval_max)
+		return -EINVAL;
+
+	mutex_lock(&input->mutex);
+
+	polldev->poll_interval = interval;
+
+	if (input->users) {
+		cancel_delayed_work_sync(&polldev->work);
+		if (polldev->poll_interval > 0)
+			input_polldev_queue_work(polldev);
+	}
+
+	mutex_unlock(&input->mutex);
+
+	return count;
+}
+
+static DEVICE_ATTR(poll, S_IRUGO | S_IWUSR, input_polldev_get_poll,
+					    input_polldev_set_poll);
+
+
+static ssize_t input_polldev_get_max(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	struct input_polled_dev *polldev = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", polldev->poll_interval_max);
+}
+
+static DEVICE_ATTR(max, S_IRUGO, input_polldev_get_max, NULL);
+
+static ssize_t input_polldev_get_min(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	struct input_polled_dev *polldev = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", polldev->poll_interval_min);
+}
+
+static DEVICE_ATTR(min, S_IRUGO, input_polldev_get_min, NULL);
+
+static struct attribute *sysfs_attrs[] = {
+	&dev_attr_poll.attr,
+	&dev_attr_max.attr,
+	&dev_attr_min.attr,
+	NULL
+};
+
+static struct attribute_group input_polldev_attribute_group = {
+	.attrs = sysfs_attrs
+};
+
 /**
  * input_allocate_polled_device - allocated memory polled device
  *
@@ -153,15 +235,29 @@ EXPORT_SYMBOL(input_free_polled_device);
 int input_register_polled_device(struct input_polled_dev *dev)
 {
 	struct input_dev *input = dev->input;
+	int error;
 
 	input_set_drvdata(input, dev);
 	INIT_DELAYED_WORK(&dev->work, input_polled_device_work);
 	if (!dev->poll_interval)
 		dev->poll_interval = 500;
+	if (!dev->poll_interval_max)
+		dev->poll_interval_max = dev->poll_interval;
 	input->open = input_open_polled_device;
 	input->close = input_close_polled_device;
 
-	return input_register_device(input);
+	error = input_register_device(input);
+	if (error)
+		return error;
+
+	error = sysfs_create_group(&input->dev.kobj,
+				   &input_polldev_attribute_group);
+	if (error) {
+		input_unregister_device(input);
+		return error;
+	}
+
+	return 0;
 }
 EXPORT_SYMBOL(input_register_polled_device);
 
@@ -177,6 +273,9 @@ EXPORT_SYMBOL(input_register_polled_device);
  */
 void input_unregister_polled_device(struct input_polled_dev *dev)
 {
+	sysfs_remove_group(&dev->input->dev.kobj,
+			   &input_polldev_attribute_group);
+
 	input_unregister_device(dev->input);
 	dev->input = NULL;
 }

include/linux/input-polldev.h

@@ -21,7 +21,12 @@
  *	longer being polled. Used to put device into low power mode.
  * @poll: driver-supplied method that polls the device and posts
  *	input events (mandatory).
- * @poll_interval: specifies how often the poll() method shoudl be called.
+ * @poll_interval: specifies how often the poll() method should be called.
+ *	Defaults to 500 msec unless overriden when registering the device.
+ * @poll_interval_max: specifies upper bound for the poll interval.
+ *	Defaults to the initial value of @poll_interval.
+ * @poll_interval_min: specifies lower bound for the poll interval.
+ *	Defaults to 0.
  * @input: input device structire associated with the polled device.
  *	Must be properly initialized by the driver (id, name, phys, bits).
  *
@@ -36,8 +41,12 @@ struct input_polled_dev {
 	void (*close)(struct input_polled_dev *dev);
 	void (*poll)(struct input_polled_dev *dev);
 	unsigned int poll_interval; /* msec */
+	unsigned int poll_interval_max; /* msec */
+	unsigned int poll_interval_min; /* msec */
 
 	struct input_dev *input;
+
+/* private: */
 	struct delayed_work work;
 };