tags 517485 fixed-upstream
thanks
Hello Alan,
On 2/28/09, Alan Curry <pac...@kosh.dhis.org> wrote:
> Package: manpages
> Severity: normal
>
>
> This description:
>
>> KDGETLED
>> Get state of LEDs. argp points to a long. The lower three bits
>> of *argp are set to the state of the LEDs, as follows:
>>
>> LED_CAP 0x04 caps lock led
>> LEC_NUM 0x02 num lock led
>> LED_SCR 0x01 scroll lock led
>
> is wrong. The kernel only stores a single byte *argp, so if you give it the
> address of a long, you won't necessarily find the results in the low 3 bits
> of the long. (It happens to work out that way if you are little-endian.)
> Change "long" to "char" and the description will be correct.
>
> Demonstration program (run it on a big-endian machine to see that the actual
> behavior is not what the man page says):
>
> #include <stdio.h>
> #include <sys/ioctl.h>
> #include <linux/kd.h>
>
> int main(void)
> {
> int ioctlret;
> long longval;
>
> longval = -1;
>
> ioctlret = ioctl(0, KDGETLED, &longval);
> printf("ioctlret=%d longval=%08lx\n", ioctlret, longval);
>
> return 0;
> }
Thanks for the excellently documented report! As you suggest, I have
changed "long" to "char", and the change will be in ustream 3.20.
Cheers,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git
man-pages online: http://www.kernel.org/doc/man-pages/online_pages.html
Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html
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