Reading keys

Reading keys

[Niko Rosvall]

Hi All,

I'm new to Linux kernel and actually subscribed to this list today.
So, i'm not even sure is this the right place to ask this, but:

I want to make a kernel module which detects a keypress and then
disables it. E.g someone presses F1 and my module would just "eat" it.

Any examples and/or hints where to start? Some nice, small peace of code
would be very very nice. 

Thanks,
Niko

Re: Reading keys

[Christoph Fritz]

On Mon, 2010-05-10 at 19:01 +0300, Niko Rosvall wrote:
> Hi All,
> 
> I'm new to Linux kernel and actually subscribed to this list today.
> So, i'm not even sure is this the right place to ask this, but:
> 
> I want to make a kernel module which detects a keypress and then
> disables it. E.g someone presses F1 and my module would just "eat" it.

Interesting usecase, is it for a kiosk? And why don't you disable the
keys in X or your application?

> Any examples and/or hints where to start? Some nice, small peace of code
> would be very very nice.

You could hack input_event() in drivers/input/input.c

Thanks,
 Christoph

Re: Reading keys

[Niko Rosvall]

On Mon, 2010-05-10 at 18:55 +0200, Christoph Fritz wrote:
> On Mon, 2010-05-10 at 19:01 +0300, Niko Rosvall wrote:
> > Hi All,
> > 
> > I'm new to Linux kernel and actually subscribed to this list today.
> > So, i'm not even sure is this the right place to ask this, but:
> > 
> > I want to make a kernel module which detects a keypress and then
> > disables it. E.g someone presses F1 and my module would just "eat" it.
> 
> Interesting usecase, is it for a kiosk? And why don't you disable the
> keys in X or your application?
> 
> > Any examples and/or hints where to start? Some nice, small peace of code
> > would be very very nice.
> 
> You could hack input_event() in drivers/input/input.c
> 
> Thanks,
>  Christoph

No, not for a kiosk or anything. Basically I'm just having fun here and
trying to do a module which would disable caps lock key completely.

Of course I can do that using xmodmap, but where's the fun then? ;)

I did modify input.c (didn't test it yet thought), but what I really
want is just a simple module so I can load and unload it when I want.

Cheers,
Niko

Re: Reading keys

[Dmitry Torokhov]

On Mon, May 10, 2010 at 10:54:23PM +0300, Niko Rosvall wrote:
> On Mon, 2010-05-10 at 18:55 +0200, Christoph Fritz wrote:
> > On Mon, 2010-05-10 at 19:01 +0300, Niko Rosvall wrote:
> > > Hi All,
> > > 
> > > I'm new to Linux kernel and actually subscribed to this list today.
> > > So, i'm not even sure is this the right place to ask this, but:
> > > 
> > > I want to make a kernel module which detects a keypress and then
> > > disables it. E.g someone presses F1 and my module would just "eat" it.
> > 
> > Interesting usecase, is it for a kiosk? And why don't you disable the
> > keys in X or your application?
> > 
> > > Any examples and/or hints where to start? Some nice, small peace of code
> > > would be very very nice.
> > 
> > You could hack input_event() in drivers/input/input.c
> > 
> > Thanks,
> >  Christoph
> 
> No, not for a kiosk or anything. Basically I'm just having fun here and
> trying to do a module which would disable caps lock key completely.
> 
> Of course I can do that using xmodmap, but where's the fun then? ;)
> 
> I did modify input.c (didn't test it yet thought), but what I really
> want is just a simple module so I can load and unload it when I want.
> 

You need to define "filter" input handler - one that implements filter()
instead of event(). This requires recent kernel though.

-- 
Dmitry