On Fri, Sep 14, 2012 at 2:12 PM, David Woodhouse <dwmw2@xxxxxxxxxxxxx> wrote: > On Fri, 2012-09-14 at 14:09 +0100, Grant Likely wrote: >> On Fri, Sep 14, 2012 at 2:01 PM, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote: >> > On Fri, 14 Sep 2012 13:57:06 +0100, Grant Likely <grant.likely@xxxxxxxxxxxx> wrote: >> >> Some platforms (for instance MacbookPros) have custom backlight drivers >> >> and don't use the integrated i915 backlight control. This patch adds a >> >> quirk to disable registering the intel backlight when unused on a >> >> platform. >> >> >> >> Tested on MacbookPro8,3. Without this patch both the intel_backlight and >> >> gmux_backlight devices get registered and userspace doesn't know which >> >> it should use. >> > >> > Userspace is informed throught the backlight/type property. >> >> Perhaps, but userspace (Ubuntu) isn't doing anything with it, and it >> still remains that it makes no sense whatsoever to register a >> backlight device that doesn't exist. > > Indeed. Userspace (well, gnome-settings-daemon) will use the backlight > provided by X, in preference to anything it finds > in /sys/class/backlight. So if the Intel one is present (and thus > exposed via X) then userspace will never bother with comparing types and > choosing the sanest backlight to use. > > See https://bugzilla.redhat.com/show_bug.cgi?id=752595 In that bug you mention that the intel backlight sets a bogus max of '1' when a backlight isn't present. I saw that too here. Here's the offending code: u32 intel_panel_get_max_backlight(struct drm_device *dev) { struct drm_i915_private *dev_priv = dev->dev_private; u32 max; max = i915_read_blc_pwm_ctl(dev_priv); if (max == 0) { /* XXX add code here to query mode clock or hardware clock * and program max PWM appropriately. */ pr_warn_once("fixme: max PWM is zero\n"); return 1; } I used a quirk in my patch, but I could instead change the driver to bail here instead of trying to limp along. g. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
