[PATCH] HID: uclogic: Add support for XP-PEN Deco LW

[José Expósito]

The XP-PEN Deco LW is a UGEE v2 device with a frame with 8 buttons.
Its pen has 2 buttons, supports tilt and pressure.

It can be connected by USB cable or using a USB Bluetooth dongle to use
it in wireless mode. When it is connected using the dongle, the device
battery is used to power it.

Its vendor, product and version are identical to the Deco L. The only
difference reported by their firmware is the product name.
In order to add support for battery reporting, add a new HID descriptor
and a quirk to detect the wireless version of the tablet.

Link: https://github.com/DIGImend/digimend-kernel-drivers/issues/635
Tested-by: Mia Kanashi <chad@xxxxxxxxxxxxx>
Tested-by: Andreas Grosse <andig.mail@xxxxxxxxxxx>
Signed-off-by: José Expósito <jose.exposito89@xxxxxxxxx>
---
 drivers/hid/hid-uclogic-params.c | 73 ++++++++++++++++++++++++++++++++
 drivers/hid/hid-uclogic-rdesc.c  | 34 +++++++++++++++
 drivers/hid/hid-uclogic-rdesc.h  |  7 +++
 3 files changed, 114 insertions(+)

diff --git a/drivers/hid/hid-uclogic-params.c b/drivers/hid/hid-uclogic-params.c
index 34fa991e6267..88b328d4dcec 100644
--- a/drivers/hid/hid-uclogic-params.c
+++ b/drivers/hid/hid-uclogic-params.c
@@ -1211,6 +1211,70 @@ static int uclogic_params_ugee_v2_init_frame_mouse(struct uclogic_params *p)
 	return rc;
 }
 
+/**
+ * uclogic_params_ugee_v2_has_battery() - check whether a UGEE v2 device has
+ * battery or not.
+ * @hdev:	The HID device of the tablet interface.
+ *
+ * Returns:
+ *	True if the device has battery, false otherwise.
+ */
+static bool uclogic_params_ugee_v2_has_battery(struct hid_device *hdev)
+{
+	/* The XP-PEN Deco LW vendor, product and version are identical to the
+	 * Deco L. The only difference reported by their firmware is the product
+	 * name. Add a quirk to support battery reporting on the wireless
+	 * version.
+	 */
+	if (hdev->vendor == USB_VENDOR_ID_UGEE &&
+	    hdev->product == USB_DEVICE_ID_UGEE_XPPEN_TABLET_DECO_L) {
+		struct usb_device *udev = hid_to_usb_dev(hdev);
+		const char *lw_name = "Deco LW";
+
+		if (strncmp(udev->product, lw_name, strlen(lw_name)) == 0)
+			return true;
+	}
+
+	return false;
+}
+
+/**
+ * uclogic_params_ugee_v2_init_battery() - initialize UGEE v2 battery reporting.
+ * @hdev:	The HID device of the tablet interface, cannot be NULL.
+ * @p:		Parameters to fill in, cannot be NULL.
+ *
+ * Returns:
+ *	Zero, if successful. A negative errno code on error.
+ */
+static int uclogic_params_ugee_v2_init_battery(struct hid_device *hdev,
+					       struct uclogic_params *p)
+{
+	int rc = 0;
+
+	if (!hdev || !p)
+		return -EINVAL;
+
+	/* Some tablets contain invalid characters in hdev->uniq, throwing a
+	 * "hwmon: '<name>' is not a valid name attribute, please fix" error.
+	 * Use the device vendor and product IDs instead.
+	 */
+	snprintf(hdev->uniq, sizeof(hdev->uniq), "%x-%x", hdev->vendor,
+		 hdev->product);
+
+	rc = uclogic_params_frame_init_with_desc(&p->frame_list[1],
+						 uclogic_rdesc_ugee_v2_battery_template_arr,
+						 uclogic_rdesc_ugee_v2_battery_template_size,
+						 UCLOGIC_RDESC_UGEE_V2_BATTERY_ID);
+	if (rc)
+		return rc;
+
+	p->frame_list[1].suffix = "Battery";
+	p->pen.subreport_list[1].value = 0xf2;
+	p->pen.subreport_list[1].id = UCLOGIC_RDESC_UGEE_V2_BATTERY_ID;
+
+	return rc;
+}
+
 /**
  * uclogic_params_ugee_v2_init() - initialize a UGEE graphics tablets by
  * discovering their parameters.
@@ -1334,6 +1398,15 @@ static int uclogic_params_ugee_v2_init(struct uclogic_params *params,
 	if (rc)
 		goto cleanup;
 
+	/* Initialize the battery interface*/
+	if (uclogic_params_ugee_v2_has_battery(hdev)) {
+		rc = uclogic_params_ugee_v2_init_battery(hdev, &p);
+		if (rc) {
+			hid_err(hdev, "error initializing battery: %d\n", rc);
+			goto cleanup;
+		}
+	}
+
 output:
 	/* Output parameters */
 	memcpy(params, &p, sizeof(*params));
diff --git a/drivers/hid/hid-uclogic-rdesc.c b/drivers/hid/hid-uclogic-rdesc.c
index 4bd54c4fb5b0..6524b4b61b25 100644
--- a/drivers/hid/hid-uclogic-rdesc.c
+++ b/drivers/hid/hid-uclogic-rdesc.c
@@ -1035,6 +1035,40 @@ const __u8 uclogic_rdesc_ugee_v2_frame_mouse_template_arr[] = {
 const size_t uclogic_rdesc_ugee_v2_frame_mouse_template_size =
 			sizeof(uclogic_rdesc_ugee_v2_frame_mouse_template_arr);
 
+/* Fixed report descriptor template for UGEE v2 battery reports */
+const __u8 uclogic_rdesc_ugee_v2_battery_template_arr[] = {
+	0x05, 0x01,         /*  Usage Page (Desktop),                   */
+	0x09, 0x07,         /*  Usage (Keypad),                         */
+	0xA1, 0x01,         /*  Collection (Application),               */
+	0x85, UCLOGIC_RDESC_UGEE_V2_BATTERY_ID,
+			    /*      Report ID,                          */
+	0x75, 0x08,         /*      Report Size (8),                    */
+	0x95, 0x02,         /*      Report Count (2),                   */
+	0x81, 0x01,         /*      Input (Constant),                   */
+	0x05, 0x84,         /*      Usage Page (Power Device),          */
+	0x05, 0x85,         /*      Usage Page (Battery System),        */
+	0x09, 0x65,         /*      Usage Page (AbsoluteStateOfCharge), */
+	0x75, 0x08,         /*      Report Size (8),                    */
+	0x95, 0x01,         /*      Report Count (1),                   */
+	0x15, 0x00,         /*      Logical Minimum (0),                */
+	0x26, 0xff, 0x00,   /*      Logical Maximum (255),              */
+	0x81, 0x02,         /*      Input (Variable),                   */
+	0x75, 0x01,         /*      Report Size (1),                    */
+	0x95, 0x01,         /*      Report Count (1),                   */
+	0x15, 0x00,         /*      Logical Minimum (0),                */
+	0x25, 0x01,         /*      Logical Maximum (1),                */
+	0x09, 0x44,         /*      Usage Page (Charging),              */
+	0x81, 0x02,         /*      Input (Variable),                   */
+	0x95, 0x07,         /*      Report Count (7),                   */
+	0x81, 0x01,         /*      Input (Constant),                   */
+	0x75, 0x08,         /*      Report Size (8),                    */
+	0x95, 0x07,         /*      Report Count (7),                   */
+	0x81, 0x01,         /*      Input (Constant),                   */
+	0xC0                /*  End Collection                          */
+};
+const size_t uclogic_rdesc_ugee_v2_battery_template_size =
+			sizeof(uclogic_rdesc_ugee_v2_battery_template_arr);
+
 /* Fixed report descriptor for Ugee EX07 frame */
 const __u8 uclogic_rdesc_ugee_ex07_frame_arr[] = {
 	0x05, 0x01,             /*  Usage Page (Desktop),                   */
diff --git a/drivers/hid/hid-uclogic-rdesc.h b/drivers/hid/hid-uclogic-rdesc.h
index 0502a0656496..a1f78c07293f 100644
--- a/drivers/hid/hid-uclogic-rdesc.h
+++ b/drivers/hid/hid-uclogic-rdesc.h
@@ -161,6 +161,9 @@ extern const size_t uclogic_rdesc_v2_frame_dial_size;
 /* Device ID byte offset in v2 frame dial reports */
 #define UCLOGIC_RDESC_V2_FRAME_DIAL_DEV_ID_BYTE	0x4
 
+/* Report ID for tweaked UGEE v2 battery reports */
+#define UCLOGIC_RDESC_UGEE_V2_BATTERY_ID 0xba
+
 /* Fixed report descriptor template for UGEE v2 pen reports */
 extern const __u8 uclogic_rdesc_ugee_v2_pen_template_arr[];
 extern const size_t uclogic_rdesc_ugee_v2_pen_template_size;
@@ -177,6 +180,10 @@ extern const size_t uclogic_rdesc_ugee_v2_frame_dial_template_size;
 extern const __u8 uclogic_rdesc_ugee_v2_frame_mouse_template_arr[];
 extern const size_t uclogic_rdesc_ugee_v2_frame_mouse_template_size;
 
+/* Fixed report descriptor template for UGEE v2 battery reports */
+extern const __u8 uclogic_rdesc_ugee_v2_battery_template_arr[];
+extern const size_t uclogic_rdesc_ugee_v2_battery_template_size;
+
 /* Fixed report descriptor for Ugee EX07 frame */
 extern const __u8 uclogic_rdesc_ugee_ex07_frame_arr[];
 extern const size_t uclogic_rdesc_ugee_ex07_frame_size;
-- 
2.25.1