[PATCH v4 7/9] drm/amd/display: Allow backlight registration to fail

["Mario Limonciello (AMD)" <superm1@kernel.org>]

[Why]
If backlight registration fails then it's ignored. This could hide
a fatal problem to a user.

[How]
Pass error codes up from backlight registration failures.

Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 41 +++++++++++--------
 1 file changed, 24 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index b6f9188a7b36..97eec889b0aa 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -5492,7 +5492,7 @@ static const struct backlight_ops amdgpu_dm_backlight_ops = {
 	.update_status	= amdgpu_dm_backlight_update_status,
 };
 
-static void
+static int
 amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector)
 {
 	struct drm_device *drm = aconnector->base.dev;
@@ -5503,15 +5503,16 @@ amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector)
 	int min, max;
 	int real_brightness;
 	int init_brightness;
+	int r;
 
 	if (aconnector->bl_idx == -1)
-		return;
+		return 0;
 
 	if (!acpi_video_backlight_use_native()) {
 		drm_info(drm, "Skipping amdgpu DM backlight registration\n");
 		/* Try registering an ACPI video backlight device instead. */
 		acpi_video_register_backlight();
-		return;
+		return 0;
 	}
 
 	caps = &dm->backlight_caps[aconnector->bl_idx];
@@ -5545,22 +5546,26 @@ amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector)
 	dm->brightness[aconnector->bl_idx] = props.brightness;
 
 	if (IS_ERR(dm->backlight_dev[aconnector->bl_idx])) {
-		drm_err(drm, "DM: Backlight registration failed!\n");
+		r = PTR_ERR(dm->backlight_dev[aconnector->bl_idx]);
+		drm_err(drm, "DM: Backlight registration failed: %d\n", r);
 		dm->backlight_dev[aconnector->bl_idx] = NULL;
-	} else {
-		/*
-		 * dm->brightness[x] can be inconsistent just after startup until
-		 * ops.get_brightness is called.
-		 */
-		real_brightness =
-			amdgpu_dm_backlight_ops.get_brightness(dm->backlight_dev[aconnector->bl_idx]);
+		return r;
+	}
 
-		if (real_brightness != init_brightness) {
-			dm->actual_brightness[aconnector->bl_idx] = real_brightness;
-			dm->brightness[aconnector->bl_idx] = real_brightness;
-		}
-		drm_dbg_driver(drm, "DM: Registered Backlight device: %s\n", bl_name);
+	/*
+	 * dm->brightness[x] can be inconsistent just after startup until
+	 * ops.get_brightness is called.
+	 */
+	real_brightness =
+		amdgpu_dm_backlight_ops.get_brightness(dm->backlight_dev[aconnector->bl_idx]);
+
+	if (real_brightness != init_brightness) {
+		dm->actual_brightness[aconnector->bl_idx] = real_brightness;
+		dm->brightness[aconnector->bl_idx] = real_brightness;
 	}
+	drm_dbg_driver(drm, "DM: Registered Backlight device: %s\n", bl_name);
+
+	return 0;
 }
 
 static int initialize_plane(struct amdgpu_display_manager *dm,
@@ -8411,7 +8416,9 @@ amdgpu_dm_connector_late_register(struct drm_connector *connector)
 			return r;
 	}
 
-	amdgpu_dm_register_backlight_device(amdgpu_dm_connector);
+	r = amdgpu_dm_register_backlight_device(amdgpu_dm_connector);
+	if (r)
+		return r;
 
 	if ((connector->connector_type == DRM_MODE_CONNECTOR_DisplayPort) ||
 	    (connector->connector_type == DRM_MODE_CONNECTOR_eDP)) {
-- 
2.54.0