[PATCH] HID: multitouch: Do not fetch initial feature reports for Win8 devices

[Mika Westerberg <mika.westerberg@linux.intel.com>]

Some newer Intel Skylake based Dell laptops with Win8 precision touchpad
fail when initial feature reports are fetched from it. Below is an
example output with some additional debug included:

 i2c_hid i2c-DLL0704:01: Fetching the HID descriptor
 i2c_hid i2c-DLL0704:01: __i2c_hid_command: cmd=20 00
 i2c_hid i2c-DLL0704:01: HID Descriptor: 1e 00 00 01 99 02 21 00 24 ...
 ...
 i2c_hid i2c-DLL0704:01: i2c_hid_get_report
 i2c_hid i2c-DLL0704:01: __i2c_hid_command: cmd=22 00 38 02 23 00
 i2c_hid i2c-DLL0704:01: report (len=4): 04 00 08 05
 i2c_hid i2c-DLL0704:01: report id 13
 i2c_hid i2c-DLL0704:01: i2c_hid_get_report
 i2c_hid i2c-DLL0704:01: __i2c_hid_command: cmd=22 00 3d 02 23 00
 i2c_hid i2c-DLL0704:01: failed to retrieve report from device.
 i2c_hid i2c-DLL0704:01: report id 7
 i2c_hid i2c-DLL0704:01: i2c_hid_get_report
 i2c_hid i2c-DLL0704:01: __i2c_hid_command: cmd=22 00 37 02 23 00
 i2c_hid i2c-DLL0704:01: report (len=259): 03 01 07 fc 28 fe 84 40 ...
 i2c_hid i2c-DLL0704:01: report id 4
 i2c_hid i2c-DLL0704:01: i2c_hid_get_report
 i2c_hid i2c-DLL0704:01: __i2c_hid_command: cmd=22 00 34 02 23 00

We manage to fetch few reports but then the touchpad dies:

 i2c_designware i2c_designware.1: i2c_dw_handle_tx_abort: lost arbitration
 i2c_hid i2c-DLL0704:01: failed to retrieve report from device.

it eventually pulls the whole I2C bus low:

 i2c_designware i2c_designware.1: controller timed out
 i2c_hid i2c-DLL0704:01: failed to set a report to device.

Fix this by preventing initial feature report fetch for Win8 devices. It
should not be needed anyway according to [1] because the two "GET"
feature reports for these devices are about device capabilities and Win8
certification status which are not related to input events.

[1] https://msdn.microsoft.com/en-us/library/windows/hardware/dn467314(v=vs.85).aspx

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
 drivers/hid/hid-multitouch.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 426b2f1a3450..1911f7698511 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -1020,14 +1020,16 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
 	/*
 	 * Handle special quirks for Windows 8 certified devices.
 	 */
-	if (id->group == HID_GROUP_MULTITOUCH_WIN_8)
+	if (id->group == HID_GROUP_MULTITOUCH_WIN_8) {
 		/*
 		 * Some multitouch screens do not like to be polled for input
-		 * reports. Fortunately, the Win8 spec says that all touches
-		 * should be sent during each report, making the initialization
-		 * of input reports unnecessary.
+		 * and feature reports. Fortunately, the Win8 spec says that all
+		 * touches should be sent during each report, making the
+		 * initialization of input reports unnecessary.
 		 */
 		hdev->quirks |= HID_QUIRK_NO_INIT_INPUT_REPORTS;
+		hdev->quirks |= HID_QUIRK_NO_INIT_REPORTS;
+	}
 
 	td = devm_kzalloc(&hdev->dev, sizeof(struct mt_device), GFP_KERNEL);
 	if (!td) {
-- 
2.5.1