On Wednesday, May 21, 2014 03:39:53 PM Hans de Goede wrote: > acpi_video_backlight_support() is supposed to be called by other (vendor > specific) firmware backlight controls, not by native / raw backlight controls > like nv_backlight. > > Userspace will normally prefer firmware interfaces over raw interfaces, so > if acpi_video backlight support is present it will use that even if > nv_backlight is registered as well. > > Except when video.use_native_backlight is present on the kernel cmdline > (or enabled through a dmi based quirk). As the name indicates the goal here > is to make only the raw interface available to userspace so that it will use > that (it only does this when it sees a win8 compliant bios). > > This is done by: > 1) Not registering any acpi_video# backlight devices; and > 2) Making acpi_video_backlight_support() return true so that other firmware > drivers, ie acer_wmi, thinkpad_acpi, dell_laptop, etc. Don't register their > own vender specific interfaces. > > Currently nouveau breaks this setup, as when acpi_video_backlight_support() > returns true, it does not register itself, resulting in no backlight control > at all. > > This is esp. going to be a problem with 3.16 which will default to > video.use_native_backlight=1, and thus nouveau based laptops with a win8 bios > will get no backlight control at all. > > This also likely explains why the previous attempt to make > video.use_native_backlight=1 the default was not a success, as without this > patch having a default of video.use_native_backlight=1 will cause regressions. > > Note this effectively reverts commit 5bead799 > > Also see: https://bugzilla.redhat.com/show_bug.cgi?id=1093171 > > Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> It would be good to have an ACK from the nouveau people for this one. > --- > drivers/gpu/drm/nouveau/nouveau_backlight.c | 9 --------- > 1 file changed, 9 deletions(-) > > diff --git a/drivers/gpu/drm/nouveau/nouveau_backlight.c b/drivers/gpu/drm/nouveau/nouveau_backlight.c > index 630f6e8..2c1e4aa 100644 > --- a/drivers/gpu/drm/nouveau/nouveau_backlight.c > +++ b/drivers/gpu/drm/nouveau/nouveau_backlight.c > @@ -31,7 +31,6 @@ > */ > > #include <linux/backlight.h> > -#include <linux/acpi.h> > > #include "nouveau_drm.h" > #include "nouveau_reg.h" > @@ -222,14 +221,6 @@ nouveau_backlight_init(struct drm_device *dev) > struct nouveau_device *device = nv_device(drm->device); > struct drm_connector *connector; > > -#ifdef CONFIG_ACPI > - if (acpi_video_backlight_support()) { > - NV_INFO(drm, "ACPI backlight interface available, " > - "not registering our own\n"); > - return 0; > - } > -#endif > - > list_for_each_entry(connector, &dev->mode_config.connector_list, head) { > if (connector->connector_type != DRM_MODE_CONNECTOR_LVDS && > connector->connector_type != DRM_MODE_CONNECTOR_eDP) > -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
