Re: [RFC][PATCH 4/5] input: serio: add support for Amstrad Delta serial keyboard port

[Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>]

(dropping Tony and e3-hacking for now)

Monday 14 December 2009 01:11:34 Janusz Krzysztofik wrote:
> Hi Dmitry,
>
> Sunday 13 December 2009 00:20:03 Dmitry Torokhov napisał(a):
> > atkbd is supposed to support PS/2 devices speaking AT keyboard protocol.
> > We also do support such devices behind dumb controllers that do not
> > allow querying the device but we expect those to at least produce the
> > standard scancodes.
>
> As far as I can understand, using the atkbd driver is not a good idea in
> this case because of the keyboard not producing standard scancodes,
> correct?
>
> Isn't the hpps2atkbd.h provided keycode table an already supported way of
> introducing exceptions to this standard scancodes requirement? Why couldn't
> this method be reused here?
>
> What I am afraid of is if the driver supposed to be created instead
> wouldn't require reiplementing most of the atkbd code.
>
> > I would need to know a bit more about the gamepad, but so far I still
> > think that current attempot of creating intermediate serio module which
> > allows to use atkbd driver is not the proper solution.
>
> I modified the serio driver to send exactly what it gets from the buffer
> and examined its output with serio_raw. The gamepad (can be connected
> simultaneously) appeared to send exactly the same scancodes as the keyboard
> did. I couldn't see how those might be destinguished whether coming from
> the keybord or from the gamepad. Thus, handling them both together as a
> single device would probably be the only option here.
>
> With both devices connected and keys pressed simultaneously, errors occure
> at the lowest level: parity check failed, invalid stop bit, etc. I don't
> think it would be possible to do anything about this. But this also means
> that trying to query them in order to get a sensible response would
> probably be not reliable.
>
> Any thoughts?
>
> Thanks,
> Janusz

Hi Dmitry,

You probably missed my last message.

Meanwhile, I've connected the Amstrad Delta keyboard to a PC. I can confirm it 
speaks PS/2 protocol and is automatically detected by atkbd/i8042 drivers. 
The initial handshake sequence actually looks exactly the same as that of a 
standard AT keyboard. The problem persists about different scancodes, giving 
wrong keystrokes.

OTOH, the Amstrad Delta gamepad seems simplified. Connected alone to a PC, 
works as well but only when i8042.dumbkbd is set. However, when both devices 
are connected in parallel, initial keyboard handshake allows for both being 
used (not simultaneously) in default 2-way i8042 mode.

Resuming, if there were a boot/module option to atkbd allowing for non-default 
scancode table, or another similiar possibility, both devices would work with 
a PC using exsisting drivers.

Even if the chance of anyone using this tiny keyboard with a PC is rather low, 
do you still suggest that creating a new, standalone keyboard driver for it 
is a good idea?

Thanks,
Janusz
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