On Fri, Sep 14, 2012 at 04:34:28PM +0100, Grant Likely wrote:
> When a backlight isn't connected to the i915 it doesn't make any sense
> to register the backlight device, but the driver currently tries to limp
> along using a max brightness value of 1. Instead, this patch makes it so
> that if the maximum PWM value cannot be determined, then the backlight
> will not be registered.
>
> Tested on MacbookPro8,3.
>
> Signed-off-by: Grant Likely <grant.likely@xxxxxxxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> Cc: David Airlie <airlied@xxxxxxxx>
> Cc: Matthew Garrett <mjg@xxxxxxxxxx>
> Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
I've already merged a rather similar patch from Jani Nikula
commit 28dcc2d60cb570d9f549c329b2f51400553412a1
Author: Jani Nikula <jani.nikula@xxxxxxxxx>
Date: Mon Sep 3 16:25:12 2012 +0300
drm/i915: do not expose a dysfunctional backlight interface to
userspace
Should land in 3.6 rsn.
-Daniel
> ---
> drivers/gpu/drm/i915/intel_panel.c | 15 ++++++++-------
> 1 file changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
> index 3df4f5f..f410c6e 100644
> --- a/drivers/gpu/drm/i915/intel_panel.c
> +++ b/drivers/gpu/drm/i915/intel_panel.c
> @@ -168,13 +168,8 @@ u32 intel_panel_get_max_backlight(struct drm_device *dev)
> 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;
> - }
> + if (max == 0)
> + return 0; /* Cannot read max PWM. Assume no backlight */
>
> if (HAS_PCH_SPLIT(dev)) {
> max >>= 16;
> @@ -413,6 +408,12 @@ int intel_panel_setup_backlight(struct drm_device *dev)
> struct backlight_properties props;
> struct drm_connector *connector;
>
> + /* Is there a backlight present? max will be zero if not */
> + if (intel_panel_get_max_backlight(dev) == 0) {
> + DRM_INFO("i915 doesn't seem to be connected to backlight\n");
> + return 0;
> + }
> +
> intel_panel_init_backlight(dev);
>
> if (dev_priv->int_lvds_connector)
> --
> 1.7.9.5
>
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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