[Intel-gfx] [PATCH 1/2] drm/i915: check VBT for supported backlight type

[Jani Nikula]

The only supported types are none and PWM. Other values are obsolete or
reserved, don't add them.

Signed-off-by: Jani Nikula <jani.nikula at intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h   |    1 +
 drivers/gpu/drm/i915/intel_bios.c |   10 ++++++++++
 drivers/gpu/drm/i915/intel_bios.h |    3 +++
 3 files changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 55addaaa8222..03f4c866bf3e 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1154,6 +1154,7 @@ struct intel_vbt_data {
 	struct edp_power_seq edp_pps;
 
 	struct {
+		bool present;
 		u16 pwm_freq_hz;
 		bool active_low_pwm;
 	} backlight;
diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index 9b986775c4b0..862ca04f7a44 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -309,6 +309,9 @@ parse_lfp_backlight(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
 	const struct bdb_lfp_backlight_data *backlight_data;
 	const struct bdb_lfp_backlight_data_entry *entry;
 
+	/* Err to enabling backlight if no backlight block. */
+	dev_priv->vbt.backlight.present = true;
+
 	backlight_data = find_section(bdb, BDB_LVDS_BACKLIGHT);
 	if (!backlight_data)
 		return;
@@ -321,6 +324,13 @@ parse_lfp_backlight(struct drm_i915_private *dev_priv, struct bdb_header *bdb)
 
 	entry = &backlight_data->data[panel_type];
 
+	dev_priv->vbt.backlight.present = entry->type == BDB_BACKLIGHT_TYPE_PWM;
+	if (!dev_priv->vbt.backlight.present) {
+		DRM_DEBUG_KMS("PWM backlight not present in VBT (type %u)\n",
+			      entry->type);
+		return;
+	}
+
 	dev_priv->vbt.backlight.pwm_freq_hz = entry->pwm_freq_hz;
 	dev_priv->vbt.backlight.active_low_pwm = entry->active_low_pwm;
 	DRM_DEBUG_KMS("VBT backlight PWM modulation frequency %u Hz, "
diff --git a/drivers/gpu/drm/i915/intel_bios.h b/drivers/gpu/drm/i915/intel_bios.h
index d02e5f93c362..036a79922391 100644
--- a/drivers/gpu/drm/i915/intel_bios.h
+++ b/drivers/gpu/drm/i915/intel_bios.h
@@ -389,6 +389,9 @@ struct bdb_lvds_lfp_data {
 	struct bdb_lvds_lfp_data_entry data[16];
 } __packed;
 
+#define BDB_BACKLIGHT_TYPE_NONE	0
+#define BDB_BACKLIGHT_TYPE_PWM	2
+
 struct bdb_lfp_backlight_data_entry {
 	u8 type:2;
 	u8 active_low_pwm:1;
-- 
1.7.9.5