drm/i915: make backlight functions take a connector

On VLV/BYT, backlight controls a per-pipe, so when adjusting the
backlight we need to pass the correct info.  So make the externally
visible backlight functions take a connector argument, which can be used
internally to figure out the pipe backlight to adjust.

v2: make connector pipe lookup check for NULL crtc (Jani)
    fixup connector check in ASLE code (Jani)
v3: make sure we take the mode config lock around lookups (Daniel)
v4: fix double unlock in panel_get_brightness (Daniel)
v5: push ASLE work into a work queue (Daniel)
v6: separate ASLE work to a prep patch, rebase (Jani)

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index e31a740..73f036b 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -9874,6 +9874,18 @@
 	drm_crtc_helper_add(&intel_crtc->base, &intel_helper_funcs);
 }
 
+enum pipe intel_get_pipe_from_connector(struct intel_connector *connector)
+{
+	struct drm_encoder *encoder = connector->base.encoder;
+
+	WARN_ON(!mutex_is_locked(&connector->base.dev->mode_config.mutex));
+
+	if (!encoder)
+		return INVALID_PIPE;
+
+	return to_intel_crtc(encoder->crtc)->pipe;
+}
+
 int intel_get_pipe_from_crtc_id(struct drm_device *dev, void *data,
 				struct drm_file *file)
 {