Re: [PATCH] change SysRq keycode for systems without SysRq key

federico ferri
2007-07-17T23:28:27Z

Andrew Morton ha scritto:
> Seems harmless enough ;)
>
> Could you please send in a suitable update to Documentation/sysrq.txt?

sorry, I should have written a few lines here...
issue solved (sorry for not CCing here, I'm shy ((: ) resulting in no
need for a patch, just the need of a recent kernel and a userspace program.

I report here the full discussion I had with Linus Torvalds, Dmitry
Torokhov (CCed to linux-input list):

>>>>> this patch adds an entry in Kconfig after 'config MAGIC_SYSRQ' which
>>>>> asks for a different keycode (replacing also KEY_SYSRQ with
>>>>> CONFIG_MAGIC_SYSRQ_KEYCODE in char/keyboard.c)
>>>>>
>>>>> Federico
>>>>
>>>> Quite frankly, I think that if we want to make something like this
>>>> configurable, it should be dynamic, not compiled-in. So that the same
>>>> kernel image can be used with different keyboards.
>>>>
>>>> Linus
>>> (I can imagine it could be done via a /proc/sysrq-keycode virtual file,
>>> but that's just one possibility)
>>>
>>> So, this should turn into a feature request...
>>> would you accept feature requests? ( :
>>>
>>> Federico
>>
>> Well, this is totally untested, and I won't guarantee that this
works at
>> all, but this is how to generally do these kinds of things..
>>
>> Linus
>>
>> ---
>> drivers/char/keyboard.c | 6 +++++-
>> 1 files changed, 5 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/char/keyboard.c b/drivers/char/keyboard.c
>> index 90965b4..e21f52b 100644
>> --- a/drivers/char/keyboard.c
>> +++ b/drivers/char/keyboard.c
>> @@ -157,6 +157,10 @@ static int sysrq_alt_use;
>> #endif
>> static int sysrq_alt;
>>
>> +static int sysrq_key = KEY_SYSRQ;
>> +module_param_named(sysrq_key, sysrq_key, uint, 0644);
>> +MODULE_PARM_DESC(sysrq_key, "The keycode to be used for sysrq");
>> +
>> /*
>> * Translation of scancodes to keycodes. We set them on only the first
>> * keyboard in the list that accepts the scancode and keycode.
>> @@ -1139,7 +1143,7 @@ static void kbd_keycode(unsigned int keycode,
int down, int hw_raw)
>> printk(KERN_WARNING "keyboard.c: can't emulate
rawmode for keycode %d\n", keycode);
>>
>> #ifdef CONFIG_MAGIC_SYSRQ /* Handle the SysRq Hack */
>> - if (keycode == KEY_SYSRQ && (sysrq_down || (down == 1 &&
sysrq_alt))) {
>> + if (keycode == sysrq_key && (sysrq_down || (down == 1 &&
sysrq_alt))) {
>> if (!sysrq_down) {
>> sysrq_down = down;
>> sysrq_alt_use = sysrq_alt;
>>
>
> YAY! it works great.
> tried with:
> # echo 183 > /sys/module/keyboard/parameters/sysrq_key
> but also keyboard.sys_rq=183 on the command line should work; I'll
> discover that on next reboot.

Yes, please do verify.

> thank you, Linus!

You're welcome.

> (now that this has done in the proper way, is this patch going to be
> merged in the tree?)

I'm certainly ok with it, but I guess it's more up to Dmitry. If he ack's
it, I can just commit it.

Dmitry? Any reason not to do this?

Linus

-------------------------------------------------------------------------------

On 7/17/07, federico ferri <xaero@inwind.it> wrote:

> Dmitry Torokhov ha scritto:
> >> Dmitry? Any reason not to do this?
> >>
> >
> > Recent kernels have the ability to remap keymap for USB keyboards via
> > EVIOCSKEYCODE ioctl (we allowed 0adjusting keymaps on PS/2 keyboards
> > for a long time). So instead of having the new parameter redefining
> > SysRq keycode Frederico can remap one of the keys on his keyboard to
> > generate KEY_SYSRQ. This way SysRq should still work if he plugs in
> > another USB keyboard that has SysRq key or a PS/2 keyboard.
>
> would setkeycodes still just work for PS2 keyboards?
> I upgraded to newer kbd-1.13 package (kernel 2.6.21), and while trying
> to change sysrq keycode still I get the old error:
>
> KDSETKEYCODE: No such device
> failed to set scancode 38b7 to keycode 84
>
> which I reported on gentoo a long time ago:
> http://bugs.gentoo.org/show_bug.cgi?id=97388
>
> (it doesn't use EVIOCSKEYCODE)
> maybe I'm not picking up the right program?
>

EVIOCSKEYCODE support for HID (USB) went in in 2.6.22-rc1.

There is keyfuzz utility you can use to play with keymaps for a
particular device:

http://0pointer.de/lennart/projects/keyfuzz/

--
Dmitry