On Thu, 2021-09-23 at 18:49 +0200, Lukasz Majczak wrote:
With patch "drm/i915/vbt: Fix backlight parsing for VBT 234+" the size of bdb_lfp_backlight_data structure has been increased, causing if-statement in the parse_lfp_backlight function that comapres this structure size to the one retrieved from BDB, always to fail for older revisions. This patch calculates expected size of the structure for a given BDB version and compares it with the value gathered from BDB. Tested on Chromebook Pixelbook (Nocturne) (reports bdb->version = 221)
Fixes: d381baad29b4 ("drm/i915/vbt: Fix backlight parsing for VBT 234+")
Tested-by: Lukasz Majczak lma@semihalf.com Signed-off-by: Lukasz Majczak lma@semihalf.com
drivers/gpu/drm/i915/display/intel_bios.c | 11 +++++++++-- drivers/gpu/drm/i915/display/intel_vbt_defs.h | 5 +++++ 2 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c index 3c25926092de..90eae6da12e0 100644 --- a/drivers/gpu/drm/i915/display/intel_bios.c +++ b/drivers/gpu/drm/i915/display/intel_bios.c @@ -428,6 +428,7 @@ parse_lfp_backlight(struct drm_i915_private *i915, const struct lfp_backlight_data_entry *entry; int panel_type = i915->vbt.panel_type; u16 level;
size_t exp_size;
backlight_data = find_section(bdb, BDB_LVDS_BACKLIGHT); if (!backlight_data)
@@ -450,9 +451,15 @@ parse_lfp_backlight(struct drm_i915_private *i915, return; }
- if (bdb->version <= 234)
exp_size = EXP_BDB_LFP_BL_DATA_SIZE_REV_234;- else if (bdb->version > 234 && bdb->version <= 236)
exp_size = EXP_BDB_LFP_BL_DATA_SIZE_REV_236;- else
exp_size = sizeof(struct bdb_lfp_backlight_data);
Usually we go by the newest(IP version, platform...) to the oldest:
if (bdb->version >= 236) exp_size = sizeof(struct bdb_lfp_backlight_data); else if (bdb->version >= 234) exp_size = offsetof(struct bdb_lfp_backlight_data, brightness_precision_bits); else exp_size = offsetof(struct bdb_lfp_backlight_data, brightness_level);
backlight_control was added in version 191 so no need to set exp_size for older versions.
- i915->vbt.backlight.type = INTEL_BACKLIGHT_DISPLAY_DDI;
- if (bdb->version >= 191 &&
get_blocksize(backlight_data) >= sizeof(*backlight_data)) {
if (bdb->version >= 191 && get_blocksize(backlight_data) >= exp_size) { const struct lfp_backlight_control_method *method;
method = &backlight_data->backlight_control[panel_type];
diff --git a/drivers/gpu/drm/i915/display/intel_vbt_defs.h b/drivers/gpu/drm/i915/display/intel_vbt_defs.h index 330077c2e588..ba9990e5983c 100644 --- a/drivers/gpu/drm/i915/display/intel_vbt_defs.h +++ b/drivers/gpu/drm/i915/display/intel_vbt_defs.h @@ -814,6 +814,11 @@ struct lfp_brightness_level { u16 reserved; } __packed;
+#define EXP_BDB_LFP_BL_DATA_SIZE_REV_234 \
- offsetof(struct bdb_lfp_backlight_data, brightness_level)
version 234 starts at brightness_level but the size of 234 data must be included to the size, so it should be: offsetof(struct bdb_lfp_backlight_data, brightness_precision_bits).
+#define EXP_BDB_LFP_BL_DATA_SIZE_REV_236 \
- offsetof(struct bdb_lfp_backlight_data, brightness_precision_bits)
struct bdb_lfp_backlight_data { u8 entry_size; struct lfp_backlight_data_entry data[16];