[PATCH] HID: multitouch: Add required quirk for Synaptics 0xcd7e device

[Rahul Rameshbabu <sergeantsagara@protonmail.com>]

Register the Synaptics device as a special multitouch device with certain
quirks that may improve usability of the touchpad device.

Reported-by: Rain <rain@sunshowers.io>
Closes: https://lore.kernel.org/linux-input/2bbb8e1d-1793-4df1-810f-cb0137341ff4@app.fastmail.com/
Signed-off-by: Rahul Rameshbabu <sergeantsagara@protonmail.com>
---

Notes:
    Theory:
    
      I think the Synaptics device in the related email to the linux-input
      mailing list requires certain quirks like MT_QUIRK_HOVERING to correctly
      reconfigure the distance configuration for multitouch events. This might
      explain why light touches were not registered originally when
      MT_CLS_DEFAULT was used by default for the device. Would like to have
      this patch tested before being merged. A Tested-by: git trailer can then
      be appended.

 drivers/hid/hid-multitouch.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 521b2ffb4244..8db4ae05febc 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -2144,6 +2144,10 @@ static const struct hid_device_id mt_devices[] = {
 			USB_DEVICE_ID_MTP_STM)},
 
 	/* Synaptics devices */
+	{ .driver_data = MT_CLS_WIN_8_FORCE_MULTI_INPUT,
+		HID_DEVICE(BUS_I2C, HID_GROUP_MULTITOUCH_WIN_8,
+			USB_VENDOR_ID_SYNAPTICS, 0xcd7e) },
+
 	{ .driver_data = MT_CLS_WIN_8_FORCE_MULTI_INPUT,
 		HID_DEVICE(BUS_I2C, HID_GROUP_MULTITOUCH_WIN_8,
 			USB_VENDOR_ID_SYNAPTICS, 0xce08) },
-- 
2.40.1