Here is a more detailed explanation about this patch, it is not related to pam, but to device input event processing.
At some point xf86-input-evdev was changed to a newer version (2.2.5 to 2.3.1 ?), and they changed the events processing :
evdev: Only send the events at synchronization time.
Instead of just posting the button/key press/release events to the
server as soon as they arrive, add them to an internal queue and post
them once we receive an EV_SYN synchronization event.
The motion events are always sent first, followed by the queued events.
There will be one motion event and possibly many queued button/key
events posted every EV_SYN event.
[...]
What happens is the additional key code that was added in previous thinkfinger patch is not sent until a real keystroke happens (when you press enter). The patch here adds a synchronisation event after the key code, so that it is immediately posted.
Here is a more detailed explanation about this patch, it is not related to pam, but to device input event processing.
At some point xf86-input-evdev was changed to a newer version (2.2.5 to 2.3.1 ?), and they changed the events processing :
evdev: Only send the events at synchronization time.
Instead of just posting the button/key press/release events to the
server as soon as they arrive, add them to an internal queue and post
them once we receive an EV_SYN synchronization event.
The motion events are always sent first, followed by the queued events.
There will be one motion event and possibly many queued button/key
events posted every EV_SYN event.
[...]
What happens is the additional key code that was added in previous thinkfinger patch is not sent until a real keystroke happens (when you press enter). The patch here adds a synchronisation event after the key code, so that it is immediately posted.
See the comments from Jon Oberheide and Philipp Gortan (mephinet) in this Gentoo Bug report : bugs.gentoo. org/show_ bug.cgi? id=298459
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