HID: usbhid: prevent unwanted events to be sent when re-opening the device
When events occurs while no one is listening to the node (hid->open == 0
and usb_kill_urb() called) some events are still stacked somewhere in
the USB (kernel or device?) stack. When the node gets reopened, these
events are drained, and this results in spurious touch down/up, or mouse
button clicks.
The problem was spotted with touchscreens in fdo bug #81781 [1], but it
actually occurs with any mouse using hid-generic or touchscreen.
A way to reproduce it is to call:
$ xinput disable 9 ; sleep 5 ; xinput enable 9
With 9 being the device ID for the touchscreen/mouse. During the "sleep",
produce some touch events or click events. When "xinput enable" is called,
at least one click is generated.
This patch tries to fix this by draining the queue for 50 msec and
during this time frame, not forwarding these old events to the hid layer.
Hans completed the explanation:
"""
Devices like mice (basically any hid device) will have a fifo
on the device side, when we stop submitting urbs to get hid reports from
it, that fifo will fill up, and when we resume we will get whatever
is there in that fifo.
"""
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