Re: [PATCH v3] drm/i915/bdb: Fix version check

On Thu, 2021-09-30 at 15:46 +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)

Reviewed-by: José Roberto de Souza jose.souza@intel.com

Tested-by: Lukasz Majczak lma@semihalf.com Signed-off-by: Lukasz Majczak lma@semihalf.com

---

drivers/gpu/drm/i915/display/intel_bios.c | 22 ++++++++++++++----- drivers/gpu/drm/i915/display/intel_vbt_defs.h | 5 +++++ 2 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c index 3c25926092de..f9776ca85de3 100644 --- a/drivers/gpu/drm/i915/display/intel_bios.c +++ b/drivers/gpu/drm/i915/display/intel_bios.c @@ -451,13 +451,23 @@ parse_lfp_backlight(struct drm_i915_private *i915, }

i915->vbt.backlight.type = INTEL_BACKLIGHT_DISPLAY_DDI;

• if (bdb->version >= 191 &&

•    get_blocksize(backlight_data) >= sizeof(*backlight_data)) {
  

• const struct lfp_backlight_control_method *method;
  

• if (bdb->version >= 191) {

• size_t exp_size;
  
  

• method = &backlight_data->backlight_control[panel_type];
  

• i915->vbt.backlight.type = method->type;
  

• i915->vbt.backlight.controller = method->controller;
  

• if (bdb->version >= 236)
  

• 	exp_size = sizeof(struct bdb_lfp_backlight_data);
  

• else if (bdb->version >= 234)
  

• 	exp_size = EXP_BDB_LFP_BL_DATA_SIZE_REV_234;
  

• else
  

• 	exp_size = EXP_BDB_LFP_BL_DATA_SIZE_REV_191;
  

• if (get_blocksize(backlight_data) >= exp_size) {
  

• 	const struct lfp_backlight_control_method *method;
  

• 	method = &backlight_data->backlight_control[panel_type];
  

• 	i915->vbt.backlight.type = method->type;
  

• 	i915->vbt.backlight.controller = method->controller;
  

• }
  

  }

  i915->vbt.backlight.pwm_freq_hz = entry->pwm_freq_hz;

diff --git a/drivers/gpu/drm/i915/display/intel_vbt_defs.h b/drivers/gpu/drm/i915/display/intel_vbt_defs.h index 330077c2e588..a2108a8f544d 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_191 \

• offsetof(struct bdb_lfp_backlight_data, brightness_level)

+#define EXP_BDB_LFP_BL_DATA_SIZE_REV_234 \

• offsetof(struct bdb_lfp_backlight_data, brightness_precision_bits)

struct bdb_lfp_backlight_data { u8 entry_size; struct lfp_backlight_data_entry data[16];