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@xxxxxxxxx>
>
> Tested-by: Lukasz Majczak <lma@xxxxxxxxxxxx>
> Signed-off-by: Lukasz Majczak <lma@xxxxxxxxxxxx>
> ---
> 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];
