linuxconsole-dev

EVIOCGKEYCODE - can't deduce arguments.

[Brad H. <bh...@bi...>]

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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?

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.

Brad
- -- 
http://linux.conf.au. 22-25Jan2003. Perth, Aust. I'm registered. Are you?
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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

Re: EVIOCGKEYCODE - can't deduce arguments.

[Brad H. <bh...@bi...>]

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On Tue, 8 Oct 2002 18:36, Vojtech Pavlik wrote:
> 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)
Of course I'm trying it on a USB keyboard! Grrr. Thought I was reading the 
code all wrong....

> Try a normal PS/2 keyboard (or a Sun keyboard, or whatever).
The keyboard has two cables. I'll give it a whirl.

> > 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.

Brad
- -- 
http://linux.conf.au. 22-25Jan2003. Perth, Aust. I'm registered. Are you?
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Re: EVIOCGKEYCODE - can't deduce arguments.

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

On Tue, Oct 08, 2002 at 06:38:23PM +1000, Brad Hards wrote:
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> On Tue, 8 Oct 2002 18:36, Vojtech Pavlik wrote:
> > 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)
> Of course I'm trying it on a USB keyboard! Grrr. Thought I was reading the 
> code all wrong....

Because the USB keyboard tells us which keys it has, we don't need a
scancode->keycode table. (We have something like that in the HID driver,
because the HID codes aren't the same as Linux keycodes, but the table
is fixed.)

For PS/2 you unfortunately cannot have a fixed table, and thus
EVIOCSKEYCODE is needed. 

Btw, the classic KD* scancode loading ioctls should now be supported as
well.

-- 
Vojtech Pavlik
SuSE Labs

Re: EVIOCGKEYCODE - can't deduce arguments.

[Brad H. <bh...@bi...>]

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On Tue, 8 Oct 2002 18:54, Vojtech Pavlik wrote:
> Because the USB keyboard tells us which keys it has, we don't need a
> scancode->keycode table. (We have something like that in the HID driver,
> because the HID codes aren't the same as Linux keycodes, but the table
> is fixed.)
Except that some people like to remap the keyboard layout. I guess you need to 
do it in userspace (ie X) now.

> For PS/2 you unfortunately cannot have a fixed table, and thus
> EVIOCSKEYCODE is needed.
>
> Btw, the classic KD* scancode loading ioctls should now be supported as
> well.
This is only on the legacy keyboard driver, right?
I'm really concentrating on the event interface.

Brad
- -- 
http://linux.conf.au. 22-25Jan2003. Perth, Aust. I'm registered. Are you?
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Re: EVIOCGKEYCODE - can't deduce arguments.

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

On Tue, Oct 08, 2002 at 07:04:32PM +1000, Brad Hards wrote:
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> On Tue, 8 Oct 2002 18:54, Vojtech Pavlik wrote:
> > Because the USB keyboard tells us which keys it has, we don't need a
> > scancode->keycode table. (We have something like that in the HID driver,
> > because the HID codes aren't the same as Linux keycodes, but the table
> > is fixed.)
> Except that some people like to remap the keyboard layout. I guess you need to 
> do it in userspace (ie X) now.
> 
> > For PS/2 you unfortunately cannot have a fixed table, and thus
> > EVIOCSKEYCODE is needed.
> >
> > Btw, the classic KD* scancode loading ioctls should now be supported as
> > well.
> This is only on the legacy keyboard driver, right?
> I'm really concentrating on the event interface.
> 
> Brad
> - -- 
> http://linux.conf.au. 22-25Jan2003. Perth, Aust. I'm registered. Are you?
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-- 
Vojtech Pavlik
SuSE Labs