Re: [linux-usb-devel] detecting when keys are being pressed on a keyboard

[Oliver Neukum <oliver@neukum.org>]

Am Montag 24 September 2007 schrieb Dmitry Torokhov:
> Hi Oliver,
> 
> On 9/24/07, Oliver Neukum <oliver@neukum.org> wrote:
> > Am Freitag 21 September 2007 schrieb Jiri Kosina:

> > > Hi Oliver,
> > >
> > > HID doesn't keep any permanent state by itself. If you want to know
> > > whether a given key is currently pressed or not, you'd have to inspect the
> > > bitfields inside input_dev*, I am afraid.
> >
> > I see no way to do this without a race condition. The field isn't locked
> > as far as I can tell.
> 
> You can take input_dev->event_lock to stop event from propagating
> through input core while you are evaluating the bits. Input lcoking
> changes are im -mm and will be merged into 2.6.24.

Hi Dmitry,

I was thinking about a second approach. As all keypresses run through
the interrupt handlers of the hid driver, how about checking the bit field
in the interrupt handler after calling hid_input_report() ?

	Regards
		Oliver