[PATCH] HID: multitouch: force retrieving of Win8 signature blob

The Synaptics 0x11e5 over I2C found in the Asus T100-CHI requires to
fetch the signature blob to actually start sending events.

With this patch, we should be close enough to the Windows driver which
checks the content of the blob at plugin to validate or not the
touchscreen.

Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=113481
regression introduced by 6d4f5440 ("HID: multitouch: Fetch feature
reports on demand for Win8 devices") which has been backported to stable.

Cc: <redacted>
Signed-off-by: Benjamin Tissoires <redacted>
---

Hi Jiri,

Let's hope this will be the final patch for Win8 touch devices. I do not
think we need much more tests from broader devices as this is really what
we use to do before 6d4f5440, and this is also what the Windows driver does.

Crossing fingers.

Cheers,
Benjamin

 drivers/hid/hid-multitouch.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 6adb788..c2cb46d 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c

@@ -396,6 +396,11 @@ static void mt_feature_mapping(struct hid_device *hdev,
 			td->is_buttonpad = true;
 
 		break;
+	case 0xff0000c5:
+		/* Retrieve the Win8 blob once to enable some devices */
+		if (usage->usage_index == 0)
+			mt_get_feature(hdev, field->report);
+		break;
 	}
 }
 

-- 
2.5.0

On Mon, 7 Mar 2016, Benjamin Tissoires wrote:

The Synaptics 0x11e5 over I2C found in the Asus T100-CHI requires to
fetch the signature blob to actually start sending events.

With this patch, we should be close enough to the Windows driver which
checks the content of the blob at plugin to validate or not the
touchscreen.

I have brought the 'Link' and 'Fixes' headers into slightly better shape 
:) and applied.

I will likely not be pushing this to Linus this week, but will make sure 
this ends up in -stable once this lands in his tree during the upcoming 
merge window, if you agree?

Thanks,

-- 
Jiri Kosina
SUSE Labs

On Mar 07 2016 or thereabouts, Jiri Kosina wrote:

On Mon, 7 Mar 2016, Benjamin Tissoires wrote:

quoted

The Synaptics 0x11e5 over I2C found in the Asus T100-CHI requires to
fetch the signature blob to actually start sending events.

With this patch, we should be close enough to the Windows driver which
checks the content of the blob at plugin to validate or not the
touchscreen.

I have brought the 'Link' and 'Fixes' headers into slightly better shape 
:) and applied.

Hehe. That seems better now, indeed.

I will likely not be pushing this to Linus this week, but will make sure 
this ends up in -stable once this lands in his tree during the upcoming 
merge window, if you agree?

OK for me. Thanks!

Cheers,
Benjamin