HID: wacom: Support switching from vendor-defined device mode on G9 and G11

A tablet PC booted into Windows may have its pen/touch hardware switched
into "Wacom mode" similar to what we do with explicitly-supported hardware.
Some devices appear to maintain this state across reboots, preventing their
use with the generic HID driver. This patch adds support for detecting the
presence of the mode switch feature report used by devices based on the G9
and G11 chips and has the HID codepath always attempt to reset the device
back to sending standard HID reports.

Fixes: https://sourceforge.net/p/linuxwacom/bugs/307/
Fixes: https://sourceforge.net/p/linuxwacom/bugs/310/
Fixes: https://github.com/linuxwacom/input-wacom/issues/15

Co-authored-by: Benjamin Tissoires <[e-mail]>
Signed-off-by: Jason Gerecke <[e-mail]>
Reviewed-by: Benjamin Tissoires <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

drivers/hid/wacom_sys.c

···
 		hid_data->inputmode = field->report->id;
 		hid_data->inputmode_index = usage->usage_index;
 		break;
+
+	case HID_UP_DIGITIZER:
+		if (field->report->id == 0x0B &&
+		    (field->application == WACOM_G9_DIGITIZER ||
+		     field->application == WACOM_G11_DIGITIZER)) {
+			wacom->wacom_wac.mode_report = field->report->id;
+			wacom->wacom_wac.mode_value = 0;
+		}
+		break;
+
+	case WACOM_G9_PAGE:
+	case WACOM_G11_PAGE:
+		if (field->report->id == 0x03 &&
+		    (field->application == WACOM_G9_TOUCHSCREEN ||
+		     field->application == WACOM_G11_TOUCHSCREEN)) {
+			wacom->wacom_wac.mode_report = field->report->id;
+			wacom->wacom_wac.mode_value = 0;
+		}
+		break;
 	}
 }
 
···
 	return 0;
 }
 
-static int wacom_set_device_mode(struct hid_device *hdev, int report_id,
-		int length, int mode)
+static int wacom_set_device_mode(struct hid_device *hdev,
+				 struct wacom_wac *wacom_wac)
 {
-	unsigned char *rep_data;
+	u8 *rep_data;
+	struct hid_report *r;
+	struct hid_report_enum *re;
+	int length;
 	int error = -ENOMEM, limit = 0;
 
-	rep_data = kzalloc(length, GFP_KERNEL);
+	if (wacom_wac->mode_report < 0)
+		return 0;
+
+	re = &(hdev->report_enum[HID_FEATURE_REPORT]);
+	r = re->report_id_hash[wacom_wac->mode_report];
+	if (!r)
+		return -EINVAL;
+
+	rep_data = hid_alloc_report_buf(r, GFP_KERNEL);
 	if (!rep_data)
-		return error;
+		return -ENOMEM;
+
+	length = hid_report_len(r);
 
 	do {
-		rep_data[0] = report_id;
-		rep_data[1] = mode;
+		rep_data[0] = wacom_wac->mode_report;
+		rep_data[1] = wacom_wac->mode_value;
 
 		error = wacom_set_report(hdev, HID_FEATURE_REPORT, rep_data,
 					 length, 1);
 		if (error >= 0)
 			error = wacom_get_report(hdev, HID_FEATURE_REPORT,
 			                         rep_data, length, 1);
-	} while (error >= 0 && rep_data[1] != mode && limit++ < WAC_MSG_RETRIES);
+	} while (error >= 0 &&
+		 rep_data[1] != wacom_wac->mode_report &&
+		 limit++ < WAC_MSG_RETRIES);
 
 	kfree(rep_data);
 
···
 static int wacom_query_tablet_data(struct hid_device *hdev,
 		struct wacom_features *features)
 {
+	struct wacom *wacom = hid_get_drvdata(hdev);
+	struct wacom_wac *wacom_wac = &wacom->wacom_wac;
+
 	if (hdev->bus == BUS_BLUETOOTH)
 		return wacom_bt_query_tablet_data(hdev, 1, features);
 
-	if (features->type == HID_GENERIC)
-		return wacom_hid_set_device_mode(hdev);
-
-	if (features->device_type & WACOM_DEVICETYPE_TOUCH) {
-		if (features->type > TABLETPC) {
-			/* MT Tablet PC touch */
-			return wacom_set_device_mode(hdev, 3, 4, 4);
-		}
-		else if (features->type == WACOM_24HDT) {
-			return wacom_set_device_mode(hdev, 18, 3, 2);
-		}
-		else if (features->type == WACOM_27QHDT) {
-			return wacom_set_device_mode(hdev, 131, 3, 2);
-		}
-		else if (features->type == BAMBOO_PAD) {
-			return wacom_set_device_mode(hdev, 2, 2, 2);
-		}
-	} else if (features->device_type & WACOM_DEVICETYPE_PEN) {
-		if (features->type <= BAMBOO_PT) {
-			return wacom_set_device_mode(hdev, 2, 2, 2);
+	if (features->type != HID_GENERIC) {
+		if (features->device_type & WACOM_DEVICETYPE_TOUCH) {
+			if (features->type > TABLETPC) {
+				/* MT Tablet PC touch */
+				wacom_wac->mode_report = 3;
+				wacom_wac->mode_value = 4;
+			} else if (features->type == WACOM_24HDT) {
+				wacom_wac->mode_report = 18;
+				wacom_wac->mode_value = 2;
+			} else if (features->type == WACOM_27QHDT) {
+				wacom_wac->mode_report = 131;
+				wacom_wac->mode_value = 2;
+			} else if (features->type == BAMBOO_PAD) {
+				wacom_wac->mode_report = 2;
+				wacom_wac->mode_value = 2;
+			}
+		} else if (features->device_type & WACOM_DEVICETYPE_PEN) {
+			if (features->type <= BAMBOO_PT) {
+				wacom_wac->mode_report = 2;
+				wacom_wac->mode_value = 2;
+			}
 		}
 	}
+
+	wacom_set_device_mode(hdev, wacom_wac);
+
+	if (features->type == HID_GENERIC)
+		return wacom_hid_set_device_mode(hdev);
 
 	return 0;
 }
···
 	}
 
 	wacom_wac->hid_data.inputmode = -1;
+	wacom_wac->mode_report = -1;
 
 	wacom->usbdev = dev;
 	wacom->intf = intf;

drivers/hid/wacom_wac.h

···
 #define WACOM_DEVICETYPE_WL_MONITOR     0x0008
 
 #define WACOM_VENDORDEFINED_PEN		0xff0d0001
+#define WACOM_G9_PAGE			0xff090000
+#define WACOM_G9_DIGITIZER		(WACOM_G9_PAGE | 0x02)
+#define WACOM_G9_TOUCHSCREEN		(WACOM_G9_PAGE | 0x11)
+#define WACOM_G11_PAGE			0xff110000
+#define WACOM_G11_DIGITIZER		(WACOM_G11_PAGE | 0x02)
+#define WACOM_G11_TOUCHSCREEN		(WACOM_G11_PAGE | 0x11)
 
 #define WACOM_PEN_FIELD(f)	(((f)->logical == HID_DG_STYLUS) || \
 				 ((f)->physical == HID_DG_STYLUS) || \
···
 	int ps_connected;
 	u8 bt_features;
 	u8 bt_high_speed;
+	int mode_report;
+	int mode_value;
 	struct hid_data hid_data;
 };