Re: [gentoo-user] Permissions of files in /sys/

[Momesso Andrea]

On Fri, Jan 09, 2009 at 05:28:40PM +0100, Andrea Momesso wrote:
> On Wed, Jan 7, 2009 at 9:47 PM, Paul Hartman
> <paul.hartman+gentoo@×××××.com> wrote:
> > On Wed, Jan 7, 2009 at 8:29 AM, Momesso Andrea <momesso.andrea@×××××.com> wrote:
> >> I'd like to make the file /sys/class/backlight/asus-laptop/brightness
> >> writeable for users, so that I don't need to be root anymore to change
> >> the brightness.
> >>
> >> Of course I can chown or chmod ot in local.start but I'm asking if there
> >> is a cleaner way.
> >
> > I guess you need to use udevinfo to get the important information
> > about /sys/class/backlight/asus-laptop/brightness and then write up a
> > rule, slap it into a file in /etc/udev/rules.d/ and enjoy your new
> > permissions. :) I don't have that device on my system so I can't
> > really suggest anything more specific.
> >
> > Here's a udev rules HOWTO that might help:
> >
> > http://www.reactivated.net/writing_udev_rules.html
> >
> > (specifically "Controlling permissions and ownership")
> >
> > Good luck :)
> > Paul
> >
> >
>
> It looks like I cannot simply write a rule to change that permission...
> After experiencing some failures I guess that udev rules can change
> permissions on /dev/ files, but not on /sys/ files...
>
> This is my case:
>
> # udevadm info -a -p /sys/class/backlight/asus-laptop/
>
>   looking at device '/class/backlight/asus-laptop':
>     KERNEL=="asus-laptop"
>     SUBSYSTEM=="backlight"
>     DRIVER==""
>     ATTR{bl_power}=="0"
>     ATTR{brightness}=="5"
>     ATTR{actual_brightness}=="5"
>     ATTR{max_brightness}=="15"
>
> And this is the rule I added in /etc/udev/rules.d/10-local.rules
>
> KERNEL=="asus-laptop", SUBSYSTEM=="backlight", GROUP="video", MODE="0660"
>
> After a reboot I still get this:
>
> # ls -la /sys/class/backlight/asus-laptop
> total 0
> drwxr-xr-x 3 root root    0 2009-01-09 15:18 .
> drwxr-xr-x 3 root root    0 2009-01-09 15:18 ..
> -r--r--r-- 1 root root 4096 2009-01-09 15:18 actual_brightness
> -rw-r--r-- 1 root root 4096 2009-01-09 15:19 bl_power
> -rw-r--r-- 1 root root 4096 2009-01-09 17:02 brightness
> -r--r--r-- 1 root root 4096 2009-01-09 15:18 max_brightness
> drwxr-xr-x 2 root root    0 2009-01-09 15:19 power
> lrwxrwxrwx 1 root root    0 2009-01-09 15:18 subsystem -> ../../backlight
> -rw-r--r-- 1 root root 4096 2009-01-09 15:18 uevent
>
> Googling a bit I found some solutions [1] [2], but all of them are
> changing the permissions at every
> boot. It works, but it looks to me a bit unclean...
> [1] http://wiki.laptop.org/go/Xfce_keybindings#Adjust_screen_brightness_buttons
> [2] http://www.thinkwiki.org/wiki/Automatically_reduce_brightness
>

Hmmm... Having not recived any answers might mean that my suspects are
right and there is no way to create an udev rule for my scope.

I think I will have to change those permissions manually at boot time

Thanks anyway for help

-- 
Momesso (TopperH) Andrea
http://topperh.blogspot.com
Jabber: topper_harley@××××××.org
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