drm/i915/bios: Get access to the tail end of the LFP data block

We need to start parsing stuff from the tail end of the LFP data block.
This is made awkward by the fact that the fp_timing table has variable
size. So we must use a bit more finesse to get the tail end, and to
make sure we allocate enough memory for it to make sure our struct
representation fits.

v2: Rebase due to the preallocation of BDB blocks
v3: Rebase due to min_size WARN relocation
v4: Document BDB_LVDS_LFP_DATA vs. BDB_LVDS_LFP_DATA_PTRS order (Jani)

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220504150440.13748-4-ville.syrjala@linux.intel.com

1 files changed, 42 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
index 4cea9c27b198..4d7953e74814 100644
--- a/drivers/gpu/drm/i915/display/intel_bios.c
+++ b/drivers/gpu/drm/i915/display/intel_bios.c
@@ -185,10 +185,14 @@ static const struct {
 	  .min_size = sizeof(struct bdb_edp), },
 	{ .section_id = BDB_LVDS_OPTIONS,
 	  .min_size = sizeof(struct bdb_lvds_options), },
+	/*
+	 * BDB_LVDS_LFP_DATA depends on BDB_LVDS_LFP_DATA_PTRS,
+	 * so keep the two ordered.
+	 */
 	{ .section_id = BDB_LVDS_LFP_DATA_PTRS,
 	  .min_size = sizeof(struct bdb_lvds_lfp_data_ptrs), },
 	{ .section_id = BDB_LVDS_LFP_DATA,
-	  .min_size = sizeof(struct bdb_lvds_lfp_data), },
+	  .min_size = 0, /* special case */ },
 	{ .section_id = BDB_LVDS_BACKLIGHT,
 	  .min_size = sizeof(struct bdb_lfp_backlight_data), },
 	{ .section_id = BDB_LFP_POWER,
@@ -203,6 +207,23 @@ static const struct {
 	  .min_size = sizeof(struct bdb_generic_dtd), },
 };
 
+static size_t lfp_data_min_size(struct drm_i915_private *i915)
+{
+	const struct bdb_lvds_lfp_data_ptrs *ptrs;
+	size_t size;
+
+	ptrs = find_section(i915, BDB_LVDS_LFP_DATA_PTRS);
+	if (!ptrs)
+		return 0;
+
+	size = sizeof(struct bdb_lvds_lfp_data);
+	if (ptrs->panel_name.table_size)
+		size = max(size, ptrs->panel_name.offset +
+			   sizeof(struct bdb_lvds_lfp_data_tail));
+
+	return size;
+}
+
 static bool validate_lfp_data_ptrs(const void *bdb,
 				   const struct bdb_lvds_lfp_data_ptrs *ptrs)
 {
@@ -490,6 +511,9 @@ static void init_bdb_blocks(struct drm_i915_private *i915,
 		enum bdb_block_id section_id = bdb_blocks[i].section_id;
 		size_t min_size = bdb_blocks[i].min_size;
 
+		if (section_id == BDB_LVDS_LFP_DATA)
+			min_size = lfp_data_min_size(i915);
+
 		init_bdb_block(i915, bdb, section_id, min_size);
 	}
 }
@@ -560,6 +584,16 @@ get_lvds_fp_timing(const struct bdb_lvds_lfp_data *data,
 	return (const void *)data + ptrs->ptr[index].fp_timing.offset;
 }
 
+static const struct bdb_lvds_lfp_data_tail *
+get_lfp_data_tail(const struct bdb_lvds_lfp_data *data,
+		  const struct bdb_lvds_lfp_data_ptrs *ptrs)
+{
+	if (ptrs->panel_name.table_size)
+		return (const void *)data + ptrs->panel_name.offset;
+	else
+		return NULL;
+}
+
 /* Parse general panel options */
 static void
 parse_panel_options(struct drm_i915_private *i915)
@@ -664,6 +698,7 @@ static void
 parse_lfp_data(struct drm_i915_private *i915)
 {
 	const struct bdb_lvds_lfp_data *data;
+	const struct bdb_lvds_lfp_data_tail *tail;
 	const struct bdb_lvds_lfp_data_ptrs *ptrs;
 
 	ptrs = find_section(i915, BDB_LVDS_LFP_DATA_PTRS);
@@ -676,6 +711,12 @@ parse_lfp_data(struct drm_i915_private *i915)
 
 	if (!i915->vbt.lfp_lvds_vbt_mode)
 		parse_lfp_panel_dtd(i915, data, ptrs);
+
+	tail = get_lfp_data_tail(data, ptrs);
+	if (!tail)
+		return;
+
+	(void)tail;
 }
 
 static void