[Arm-netbook] Warning about tablets/netbooks with detachable keyboards

[dumblob]

Hi Albert,

Speaking of which, only the drivers should be affected by detaching /
> attaching a detachable keyboard, and precisely, the drivers should
> handle things so that upper layers don't need to care about the
> keyboard attached/detached state (except very specific parts of the UI,
> e.g. to show the detached/attached state and/or pop up a software
> keyboard when the HW one is not here and keyboard input is needed). Most
> certainly "all daemons up to GUI" should not be involved IMO.


Actually, not only driver needs to know it. Kernel needs to correctly pass
the info about what has happened to HAL (udev, etc.), then daemons reacting
to attaching/detaching devices (dbus, *bus, systemd, running terminals,
PAM, etc.) up to GUI (window manager must not reset the layout; all input
methods like SCIM/IBus/uim must preserve all pressed states etc.; mappings
of different long-running applications like widgets or icons in tray should
keep their state; user shortcuts must not get lost; running applications
should not reset any input streams to not interrupt the current
functionality, etc.).

All these have to handle the interruptions in a way, that they exactly (!)
set the full device state back to the state before interruption. They also
need to support these interruptions coming very quickly consecutively (e.g.
each milisecond).

Basically such interruption demands a full hot swap functionality, which is
basically not present anywhere in the stack I described above (yeah, 99.99%
daemons and applications count on the fact, that the initial state will not
change during their runtime).

It's really extremely frustrating when an old USB connector looses contact
for a milisecond and my external keyboard gets redected and all the
settings are totally lost (in terminal a different keyboard and without my
key bindings - which might be impossible to manually reset because of the
need of root permissions; the same in X except for the root permissions;
the same with all running applications; the same everywhere). An extreme
case are security modules (e.g. YubiKey) or security SW demanding
uninterrupted connection of a certain device (due to possible MiM attacks
etc.).

Just my 2 cents from real world.

-- Jan
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