HID: wacom: Ensure bootloader PID is usable in hidraw mode

Some Wacom devices have a special "bootloader" mode that is used for
firmware flashing. When operating in this mode, the device cannot be
used for input, and the HID descriptor is not able to be processed by
the driver. The driver generates an "Unknown device_type" warning and
then returns an error code from wacom_probe(). This is a problem because
userspace still needs to be able to interact with the device via hidraw
to perform the firmware flash.

This commit adds a non-generic device definition for 056a:0094 which
is used when devices are in "bootloader" mode. It marks the devices
with a special BOOTLOADER type that is recognized by wacom_probe() and
wacom_raw_event(). When we see this type we ensure a hidraw device is
created and otherwise keep our hands off so that userspace is in full
control.
Signed-off-by: Jason Gerecke <jason.gerecke@wacom.com>
Tested-by: Tatsunosuke Tobita <tatsunosuke.tobita@wacom.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/wacom_sys.c

@@ -155,6 +155,9 @@ static int wacom_raw_event(struct hid_device *hdev, struct hid_report *report,
 {
 	struct wacom *wacom = hid_get_drvdata(hdev);
 
+	if (wacom->wacom_wac.features.type == BOOTLOADER)
+		return 0;
+
 	if (size > WACOM_PKGLEN_MAX)
 		return 1;
 
@@ -2785,6 +2788,11 @@ static int wacom_probe(struct hid_device *hdev,
 		return error;
 	}
 
+	if (features->type == BOOTLOADER) {
+		hid_warn(hdev, "Using device in hidraw-only mode");
+		return hid_hw_start(hdev, HID_CONNECT_HIDRAW);
+	}
+
 	error = wacom_parse_and_register(wacom, false);
 	if (error)
 		return error;

drivers/hid/wacom_wac.c

@@ -4882,6 +4882,9 @@ static const struct wacom_features wacom_features_0x3dd =
 static const struct wacom_features wacom_features_HID_ANY_ID =
 	{ "Wacom HID", .type = HID_GENERIC, .oVid = HID_ANY_ID, .oPid = HID_ANY_ID };
 
+static const struct wacom_features wacom_features_0x94 =
+	{ "Wacom Bootloader", .type = BOOTLOADER };
+
 #define USB_DEVICE_WACOM(prod)						\
 	HID_DEVICE(BUS_USB, HID_GROUP_WACOM, USB_VENDOR_ID_WACOM, prod),\
 	.driver_data = (kernel_ulong_t)&wacom_features_##prod
@@ -4955,6 +4958,7 @@ const struct hid_device_id wacom_ids[] = {
 	{ USB_DEVICE_WACOM(0x84) },
 	{ USB_DEVICE_WACOM(0x90) },
 	{ USB_DEVICE_WACOM(0x93) },
+	{ USB_DEVICE_WACOM(0x94) },
 	{ USB_DEVICE_WACOM(0x97) },
 	{ USB_DEVICE_WACOM(0x9A) },
 	{ USB_DEVICE_WACOM(0x9F) },

drivers/hid/wacom_wac.h

@@ -243,6 +243,7 @@ enum {
 	MTTPC,
 	MTTPC_B,
 	HID_GENERIC,
+	BOOTLOADER,
 	MAX_TYPE
 };