HID: cypress: Support Varmilo Keyboards' media hotkeys

The Varmilo VA104M Keyboard (04b4:07b1, reported as Varmilo Z104M)
exposes media control hotkeys as a USB HID consumer control device, but
these keys do not work in the current (5.8-rc1) kernel due to the
incorrect HID report descriptor. Fix the problem by modifying the
internal HID report descriptor.

More specifically, the keyboard report descriptor specifies the
logical boundary as 572~10754 (0x023c ~ 0x2a02) while the usage
boundary is specified as 0~10754 (0x00 ~ 0x2a02). This results in an
incorrect interpretation of input reports, causing inputs to be ignored.
By setting the Logical Minimum to zero, we align the logical boundary
with the Usage ID boundary.

Some notes:

* There seem to be multiple variants of the VA104M keyboard. This
patch specifically targets 04b4:07b1 variant.

* The device works out-of-the-box on Windows platform with the generic
consumer control device driver (hidserv.inf). This suggests that
Windows either ignores the Logical Minimum/Logical Maximum or
interprets the Usage ID assignment differently from the linux
implementation; Maybe there are other devices out there that only
works on Windows due to this problem?

Signed-off-by: Frank Yang <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

drivers/hid/hid-cypress.c

···
 #define CP_2WHEEL_MOUSE_HACK		0x02
 #define CP_2WHEEL_MOUSE_HACK_ON		0x04
 
+#define VA_INVAL_LOGICAL_BOUNDARY	0x08
+
 /*
  * Some USB barcode readers from cypress have usage min and usage max in
  * the wrong order
  */
-static __u8 *cp_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+static __u8 *cp_rdesc_fixup(struct hid_device *hdev, __u8 *rdesc,
 		unsigned int *rsize)
 {
-	unsigned long quirks = (unsigned long)hid_get_drvdata(hdev);
 	unsigned int i;
-
-	if (!(quirks & CP_RDESC_SWAPPED_MIN_MAX))
-		return rdesc;
 
 	if (*rsize < 4)
 		return rdesc;
···
 			rdesc[i + 2] = 0x29;
 			swap(rdesc[i + 3], rdesc[i + 1]);
 		}
+	return rdesc;
+}
+
+static __u8 *va_logical_boundary_fixup(struct hid_device *hdev, __u8 *rdesc,
+		unsigned int *rsize)
+{
+	/*
+	 * Varmilo VA104M (with VID Cypress and device ID 07B1) incorrectly
+	 * reports Logical Minimum of its Consumer Control device as 572
+	 * (0x02 0x3c). Fix this by setting its Logical Minimum to zero.
+	 */
+	if (*rsize == 25 &&
+			rdesc[0] == 0x05 && rdesc[1] == 0x0c &&
+			rdesc[2] == 0x09 && rdesc[3] == 0x01 &&
+			rdesc[6] == 0x19 && rdesc[7] == 0x00 &&
+			rdesc[11] == 0x16 && rdesc[12] == 0x3c && rdesc[13] == 0x02) {
+		hid_info(hdev,
+			 "fixing up varmilo VA104M consumer control report descriptor\n");
+		rdesc[12] = 0x00;
+		rdesc[13] = 0x00;
+	}
+	return rdesc;
+}
+
+static __u8 *cp_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+		unsigned int *rsize)
+{
+	unsigned long quirks = (unsigned long)hid_get_drvdata(hdev);
+
+	if (quirks & CP_RDESC_SWAPPED_MIN_MAX)
+		rdesc = cp_rdesc_fixup(hdev, rdesc, rsize);
+	if (quirks & VA_INVAL_LOGICAL_BOUNDARY)
+		rdesc = va_logical_boundary_fixup(hdev, rdesc, rsize);
+
 	return rdesc;
 }
 
···
 		.driver_data = CP_RDESC_SWAPPED_MIN_MAX },
 	{ HID_USB_DEVICE(USB_VENDOR_ID_CYPRESS, USB_DEVICE_ID_CYPRESS_MOUSE),
 		.driver_data = CP_2WHEEL_MOUSE_HACK },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_CYPRESS, USB_DEVICE_ID_CYPRESS_VARMILO_VA104M_07B1),
+		.driver_data = VA_INVAL_LOGICAL_BOUNDARY },
 	{ }
 };
 MODULE_DEVICE_TABLE(hid, cp_devices);

drivers/hid/hid-ids.h

···
 #define USB_DEVICE_ID_CYPRESS_BARCODE_4	0xed81
 #define USB_DEVICE_ID_CYPRESS_TRUETOUCH	0xc001
 
+#define USB_DEVICE_ID_CYPRESS_VARMILO_VA104M_07B1   0X07b1
+
 #define USB_VENDOR_ID_DATA_MODUL	0x7374
 #define USB_VENDOR_ID_DATA_MODUL_EASYMAXTOUCH	0x1201