[PATCH 5.14 085/151] drm/i915/bdb: Fix version check

Greg Kroah-Hartman
2021-10-11T14:07:49Z

From: Lukasz Majczak <lma@semihalf.com>

[ Upstream commit fdddf8c3a477f77b3a623f220e78d45e89fc50d5 ]

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>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210930134606.227234-1-lma@semihalf.com
(cherry picked from commit 4378daf5d04eed59724e6d0e74755e17dce2e105)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 aa667fa71158..106f696e50a0 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 dbe24d7e7375..cf1ffe4a0e46 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];
--
2.33.0