HID: wacom: implement generic HID handling for pen generic devices

ISDv4 and v5 are plain HID devices. We can directly implement a generic
HID parsing/handling and remove the need to manually add those PID in
the list of supported devices.

This patch implements the pen support only. The finger part will come in
a later patch.

To be properly notified of an .event() and a .report(), we need to force
hid-core to go through the HID parsing. By default, wacom.ko binds only
hidraw, so the hid parsing is not done by hid-core. When a true HID device
is there, we add the flag HID_CLAIMED_DRIVER to hid->claimed which will
force hid-core to parse the incoming reports.
(Note that this can be easily backported by directly setting the .claimed
flag to HID_CLAIMED_DRIVER even if hid-core does not support
HID_CONNECT_DRIVER)

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Acked-by: Jason Gerecke <killertofu@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/wacom.h

@@ -89,6 +89,7 @@
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
+#include <linux/hid.h>
 #include <linux/usb/input.h>
 #include <linux/power_supply.h>
 #include <asm/unaligned.h>
@@ -143,4 +144,9 @@ 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);
+void wacom_wac_usage_mapping(struct hid_device *hdev,
+		struct hid_field *field, struct hid_usage *usage);
+int wacom_wac_event(struct hid_device *hdev, struct hid_field *field,
+		struct hid_usage *usage, __s32 value);
+void wacom_wac_report(struct hid_device *hdev, struct hid_report *report);
 #endif