Input: wacom - create a separate input device for pads

Currently, the pad events are sent through the stylus input device
for the Intuos/Cintiqs, and through the touch input device for the
Bamboos.

To differentiate the buttons pressed on the pad from the ones pressed
on the stylus, the Intuos/Cintiq uses MISC_SERIAL and ABS_MISC. This
lead to a multiplexing of the events into one device, which are then
splitted out in xf86-input-wacom. Bamboos are not using MISC events
because the pad is attached to the touch interface, and only BTN_TOUCH
is used for the finger (and DOUBLE_TAP, etc...). However, the user space
driver still splits out the pad from the touch interface in the same
way it does for the pro line devices.

The other problem we can see with this fact is that some of the Intuos
and Cintiq have a wheel, and the effective range of the reported values
is [0..71]. Unfortunately, the airbrush stylus also sends wheel events
(there is a small wheel on it), but in the range [0..1023]. From the user
space point of view it is kind of difficult to understand that because
the wheel on the pad are quite common, while the airbrush tool is not.

A solution to fix all of these problems is to split out the pad device
from the stylus/touch. This decision makes more sense because the pad is
not linked to the absolute position of the finger or pen, and usually, the
events from the pad are filtered out by the compositor, which then convert
them into actions or keyboard shortcuts.

For backward compatibility with current xf86-input-wacom, the pad devices
still present the ABS_X, ABS_Y and ABS_MISC events, but they can be
completely ignored in the new implementation.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Reviewed-by: Ping Cheng <pingc@wacom.com>
Reviewed-by: Jason Gerecke <killertofu@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/tablet/wacom.h

@@ -136,4 +136,6 @@ void wacom_wac_irq(struct wacom_wac *wacom_wac, size_t len);
 void wacom_setup_device_quirks(struct wacom_features *features);
 int wacom_setup_input_capabilities(struct input_dev *input_dev,
 				   struct wacom_wac *wacom_wac);
+int wacom_setup_pad_input_capabilities(struct input_dev *input_dev,
+				       struct wacom_wac *wacom_wac);
 #endif

drivers/input/tablet/wacom_sys.c

@@ -135,6 +135,9 @@ static int wacom_open(struct input_dev *dev)
 
 	mutex_lock(&wacom->lock);
 
+	if (wacom->open)
+		goto out;
+
 	if (usb_submit_urb(wacom->irq, GFP_KERNEL)) {
 		retval = -EIO;
 		goto out;
@@ -157,9 +160,14 @@ static void wacom_close(struct input_dev *dev)
 	autopm_error = usb_autopm_get_interface(wacom->intf);
 
 	mutex_lock(&wacom->lock);
+	if (!wacom->open)
+		goto out;
+
 	usb_kill_urb(wacom->irq);
 	wacom->open = false;
 	wacom->intf->needs_remote_wakeup = 0;
+
+out:
 	mutex_unlock(&wacom->lock);
 
 	if (!autopm_error)
@@ -1112,19 +1120,16 @@ static void wacom_destroy_battery(struct wacom *wacom)
 	}
 }
 
-static int wacom_register_input(struct wacom *wacom)
+static struct input_dev *wacom_allocate_input(struct wacom *wacom)
 {
 	struct input_dev *input_dev;
 	struct usb_interface *intf = wacom->intf;
 	struct usb_device *dev = interface_to_usbdev(intf);
 	struct wacom_wac *wacom_wac = &(wacom->wacom_wac);
-	int error;
 
 	input_dev = input_allocate_device();
-	if (!input_dev) {
-		error = -ENOMEM;
-		goto fail1;
-	}
+	if (!input_dev)
+		return NULL;
 
 	input_dev->name = wacom_wac->name;
 	input_dev->phys = wacom->phys;
@@ -1134,21 +1139,59 @@ static int wacom_register_input(struct wacom *wacom)
 	usb_to_input_id(dev, &input_dev->id);
 	input_set_drvdata(input_dev, wacom);
 
+	return input_dev;
+}
+
+static int wacom_register_input(struct wacom *wacom)
+{
+	struct input_dev *input_dev, *pad_input_dev;
+	struct wacom_wac *wacom_wac = &(wacom->wacom_wac);
+	int error;
+
+	input_dev = wacom_allocate_input(wacom);
+	pad_input_dev = wacom_allocate_input(wacom);
+	if (!input_dev || !pad_input_dev) {
+		error = -ENOMEM;
+		goto fail1;
+	}
+
 	wacom_wac->input = input_dev;
+	wacom_wac->pad_input = pad_input_dev;
+	wacom_wac->pad_input->name = wacom_wac->pad_name;
+
 	error = wacom_setup_input_capabilities(input_dev, wacom_wac);
 	if (error)
-		goto fail1;
+		goto fail2;
 
 	error = input_register_device(input_dev);
 	if (error)
 		goto fail2;
 
+	error = wacom_setup_pad_input_capabilities(pad_input_dev, wacom_wac);
+	if (error) {
+		/* no pad in use on this interface */
+		input_free_device(pad_input_dev);
+		wacom_wac->pad_input = NULL;
+		pad_input_dev = NULL;
+	} else {
+		error = input_register_device(pad_input_dev);
+		if (error)
+			goto fail3;
+	}
+
 	return 0;
 
+fail3:
+	input_unregister_device(input_dev);
+	input_dev = NULL;
 fail2:
-	input_free_device(input_dev);
 	wacom_wac->input = NULL;
+	wacom_wac->pad_input = NULL;
 fail1:
+	if (input_dev)
+		input_free_device(input_dev);
+	if (pad_input_dev)
+		input_free_device(pad_input_dev);
 	return error;
 }
 
@@ -1367,6 +1410,8 @@ static int wacom_probe(struct usb_interface *intf, const struct usb_device_id *i
 	wacom_calculate_res(features);
 
 	strlcpy(wacom_wac->name, features->name, sizeof(wacom_wac->name));
+	snprintf(wacom_wac->pad_name, sizeof(wacom_wac->pad_name),
+		"%s Pad", features->name);
 
 	if (features->quirks & WACOM_QUIRK_MULTI_INPUT) {
 		struct usb_device *other_dev;
@@ -1441,6 +1486,8 @@ static void wacom_disconnect(struct usb_interface *intf)
 	cancel_work_sync(&wacom->work);
 	if (wacom->wacom_wac.input)
 		input_unregister_device(wacom->wacom_wac.input);
+	if (wacom->wacom_wac.pad_input)
+		input_unregister_device(wacom->wacom_wac.pad_input);
 	wacom_destroy_battery(wacom);
 	wacom_destroy_leds(wacom);
 	usb_free_urb(wacom->irq);

drivers/input/tablet/wacom_wac.c

@@ -1489,8 +1489,11 @@ void wacom_wac_irq(struct wacom_wac *wacom_wac, size_t len)
 		break;
 	}
 
-	if (sync)
+	if (sync) {
 		input_sync(wacom_wac->input);
+		if (wacom_wac->pad_input)
+			input_sync(wacom_wac->pad_input);
+	}
 }
 
 static void wacom_setup_cintiq(struct wacom_wac *wacom_wac)
@@ -1939,6 +1942,28 @@ int wacom_setup_input_capabilities(struct input_dev *input_dev,
 	return 0;
 }
 
+int wacom_setup_pad_input_capabilities(struct input_dev *input_dev,
+				   struct wacom_wac *wacom_wac)
+{
+	struct wacom_features *features = &wacom_wac->features;
+
+	input_dev->evbit[0] |= BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
+
+	/* kept for making legacy xf86-input-wacom working with the wheels */
+	__set_bit(ABS_MISC, input_dev->absbit);
+
+	/* kept for making legacy xf86-input-wacom accepting the pad */
+	input_set_abs_params(input_dev, ABS_X, 0, 1, 0, 0);
+	input_set_abs_params(input_dev, ABS_Y, 0, 1, 0, 0);
+
+	switch (features->type) {
+	default:
+		/* no pad supported */
+		return 1;
+	}
+	return 0;
+}
+
 static const struct wacom_features wacom_features_0x00 =
 	{ "Wacom Penpartner",     WACOM_PKGLEN_PENPRTN,    5040,  3780,  255,
 	  0, PENPARTNER, WACOM_PENPRTN_RES, WACOM_PENPRTN_RES };

drivers/input/tablet/wacom_wac.h

@@ -150,6 +150,7 @@ struct wacom_shared {
 
 struct wacom_wac {
 	char name[WACOM_NAME_MAX];
+	char pad_name[WACOM_NAME_MAX];
 	unsigned char *data;
 	int tool[2];
 	int id[2];
@@ -157,6 +158,7 @@ struct wacom_wac {
 	struct wacom_features features;
 	struct wacom_shared *shared;
 	struct input_dev *input;
+	struct input_dev *pad_input;
 	int pid;
 	int battery_capacity;
 	int num_contacts_left;