Re: EVIOCGKEYCODE - can't deduce arguments.

[Vojtech P. <vo...@su...>]

On Tue, Oct 08, 2002 at 01:05:15PM +1000, Brad Hards wrote:

> I'm trying to finish off my documentation, and it's down to EVIOC[G,S]KEYCODE.
> 
> The problem is that I don't think I understand what the arguments are.
> 
> EVIOCGKEYCODE takes a int[2], and the first int looks like it should be passed 
> in (ie I set int[0] to some value, then call ioctl(fd, EVIOCGKEYCODE, int), 
> and then read back the other value in int[1]).
> 
> I guess that the first argument is a scancode, and the second is a keycode.
> 
> However when I pass in what I think is a reasonable value (as given by 
> showkeys -s), I'm getting -EINVAL.
> 
> Example: showkey -s gives me 0x39 for a space bar held down. I assumed if I   
> 
> codes[0] = 0x39;
> if(ioctl(fd, EVIOCGKEYCODE, codes))
>     perror("evdev ioctl");
> printf("[0]= %d, [1] = %d\n", codes[0], codes[1]);
> 
> Then I would get back codes[1] == KEY_SPACE.
> 
> However I get
> evdev ioctl: Invalid argument
> [0]= 57, [1] = 1073784704
> 
> Anyone familiar with this? Or can provide a hint?

Are you by any chance trying to do this on a USB keyboard? Bad luck, USB
keyboards don't have scancode->keycode tables. (at least not yet)

Try a normal PS/2 keyboard (or a Sun keyboard, or whatever).

> I guess EVIOCSKEYCODE just assignes the int[1] keycode to the int[0] scancode. 
> I can't make that work until I understand the scancodes business more, I 
> think.

Yep.

-- 
Vojtech Pavlik
SuSE Labs