Mailinglist Archive: opensuse-kernel (110 mails)

[Takashi Iwai <tiwai@xxxxxxx>]

At Thu, 20 Oct 2011 15:59:32 +0200,
Guido Berhoerster wrote:
> * Greg KH <gregkh@xxxxxxx> [2011-10-20 15:37]:
> > On Thu, Oct 20, 2011 at 02:59:05PM +0200, Guido Berhoerster wrote:
> > > Hi,
> > > can anyone give me a rough estimation of the level of sysfs
> > > support for setting backlight brightness on common hardware
> > > compared to xrandr?
> >
> > They are two totally different things.
> >
> > > Basically, xfce4-power-manager has a bug in the xrandr backend
> > > making it crash on resume
> > > (https://bugzilla.novell.com/show_bug.cgi?id=707127,
> > > https://bugzilla.xfce.org/show_bug.cgi?id=7851) and since
> > > upstream is unresponsive I'm wondering what the cost/benefit of
> > > temporarily disabling the xrandr backend would be, ie. whether
> > > disabling the xrandr backend and relying exclusively on the sysfs
> > > backend would break brightness manipulation for a large number
> > > of users.
> >
> > xrandr should be using the sysfs interface the kernel exposes, if it is
> > present, otherwise, it might try to use some other interface, but it
> > should always be trying to use the sysfs one if it is there.
>
> Thanks for the explanation, x-p-m can instead of xrandr use a
> privileged helper binary to manipulate sysfs directly. How
> prevalent is the kernel support for manipulating brightness via
> sysfs (relative to any of the "other interfaces" xrandr might
> use)?

Well, are you sure that the culprit is really xrandr?  To me, the bug
looks like a problem in the battery handler itself.

In the recent kernels, the battery sysfs entry is once removed and
re-added at each time upon suspend/resume (don't ask me why).  This
will trigger udev, and xfm-pm would react to delete and add the object
accordingly.  Meanwhile, it calls the notification via X idle
mechanism, so the crashing path might be called after removing the
battery device.

If this is the case, a workaround would be to cancel the pending
idle call via g_idle_remove_by_data() in xfpm_battery_finalize().


Takashi
-- 
To unsubscribe, e-mail: opensuse-kernel+unsubscribe@xxxxxxxxxxxx
To contact the owner, e-mail: opensuse-kernel+owner@xxxxxxxxxxxx