HID: multitouch: handle faulty Elo touch device

Since kernel v5.0, one single win8 touchscreen device failed.
And it turns out this is because it reports 2 InRange usage per touch.

It's a first, and I *really* wonder how this was allowed by Microsoft in
the first place. But IIRC, Breno told me this happened *after* a firmware
upgrade...

Anyway, better be safe for those crappy devices, and make sure we have
a full slot before jumping to the next.
This won't prevent all crappy devices to fail here, but at least we will
have a safeguard as long as the contact ID and the X and Y coordinates
are placed in the report after the grabage.

Fixes: 01eaac7e5713 ("HID: multitouch: remove one copy of values")
CC: stable@vger.kernel.org # v5.0+
Reported-and-tested-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index c02d4cad1893f8790e7d07a52c5730a5eac44aa2..1565a307170aa43a878890cc3d6bfb8516c6dcc7 100644 (file)
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -641,6 +641,13 @@ static void mt_store_field(struct hid_device *hdev,
        if (*target != DEFAULT_TRUE &&
            *target != DEFAULT_FALSE &&
            *target != DEFAULT_ZERO) {
+               if (usage->contactid == DEFAULT_ZERO ||
+                   usage->x == DEFAULT_ZERO ||
+                   usage->y == DEFAULT_ZERO) {
+                       hid_dbg(hdev,
+                               "ignoring duplicate usage on incomplete");
+                       return;
+               }
                usage = mt_allocate_usage(hdev, application);
                if (!usage)
                        return;