[PATCH 2/4] Input: wacom: Override 'pressure_max' with value from HID_USAGE_PRESSURE

[Jason Gerecke <killertofu@gmail.com>]

The 0xEC sensor is used in multiple tablet PCs and curiously has
versions that report 256 levels of pressure (Samsung Slate 7)
as well as versions that report 1024 levels (Lenovo Thinkpad Yoga).
To allow both versions to work properly, we allow the value of
HID_USAGE_PRESSURE reported to override pressure_max.

Signed-off-by: Jason Gerecke <killertofu@gmail.com>
---
 drivers/input/tablet/wacom_sys.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/input/tablet/wacom_sys.c b/drivers/input/tablet/wacom_sys.c
index 5be6177..611fc39 100644
--- a/drivers/input/tablet/wacom_sys.c
+++ b/drivers/input/tablet/wacom_sys.c
@@ -24,6 +24,7 @@
 #define HID_USAGE			0x09
 #define HID_USAGE_X			((HID_USAGE_PAGE_DESKTOP << 16) | 0x30)
 #define HID_USAGE_Y			((HID_USAGE_PAGE_DESKTOP << 16) | 0x31)
+#define HID_USAGE_PRESSURE		((HID_USAGE_PAGE_DIGITIZER << 16) | 0x30)
 #define HID_USAGE_X_TILT		((HID_USAGE_PAGE_DIGITIZER << 16) | 0x3d)
 #define HID_USAGE_Y_TILT		((HID_USAGE_PAGE_DIGITIZER << 16) | 0x3e)
 #define HID_USAGE_FINGER		((HID_USAGE_PAGE_DIGITIZER << 16) | 0x22)
@@ -465,6 +466,14 @@ static int wacom_parse_hid(struct usb_interface *intf,
 					wacom_retrieve_report_data(intf, features);
 				i++;
 				break;
+
+			case HID_USAGE_PRESSURE:
+				if (pen) {
+					features->pressure_max =
+						get_unaligned_le16(&report[i + 3]);
+					i += 4;
+				}
+				break;
 			}
 			break;
 
-- 
1.8.5.3