On Thu, 18 Aug 2022, Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > The current scheme for generating the LFP data table pointers > (when the block including them is missing from the VBT) expects > the 0xffff sequence to only appear in the fp_timing terminator > entries. However some VBTs also have extra 0xffff sequences > elsewhere in the LFP data. When looking for the terminators > we may end up finding those extra sequeneces insted, which means > we deduce the wrong size for the fp_timing table. The code > then notices the inconsistent looking values and gives up on > the generated data table pointers, preventing us from parsing > the LFP data table entirely. > > Let's give up on the "search for the terminators" approach > and instead just hardcode the expected size for the fp_timing > table. > > We have enough sanity checks in place to make sure we > shouldn't end up parsing total garbage even if that size > should change in the future (although that seems unlikely > as the fp_timing and dvo_timing tables have been declared > obsolete as of VBT version 229). > > Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/6592 > Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> What a mess. Could debug log about missing data ptrs on vbt version < 155, but no biggie. Reviewed-by: Jani Nikula <jani.nikula@xxxxxxxxx> > --- > drivers/gpu/drm/i915/display/intel_bios.c | 46 +++++++++-------------- > 1 file changed, 18 insertions(+), 28 deletions(-) > > diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c > index f1f861da9e93..f54a1843924e 100644 > --- a/drivers/gpu/drm/i915/display/intel_bios.c > +++ b/drivers/gpu/drm/i915/display/intel_bios.c > @@ -337,18 +337,6 @@ static bool fixup_lfp_data_ptrs(const void *bdb, void *ptrs_block) > return validate_lfp_data_ptrs(bdb, ptrs); > } > > -static const void *find_fp_timing_terminator(const u8 *data, int size) > -{ > - int i; > - > - for (i = 0; i < size - 1; i++) { > - if (data[i] == 0xff && data[i+1] == 0xff) > - return &data[i]; > - } > - > - return NULL; > -} > - > static int make_lfp_data_ptr(struct lvds_lfp_data_ptr_table *table, > int table_size, int total_size) > { > @@ -372,11 +360,22 @@ static void next_lfp_data_ptr(struct lvds_lfp_data_ptr_table *next, > static void *generate_lfp_data_ptrs(struct drm_i915_private *i915, > const void *bdb) > { > - int i, size, table_size, block_size, offset; > - const void *t0, *t1, *block; > + int i, size, table_size, block_size, offset, fp_timing_size; > struct bdb_lvds_lfp_data_ptrs *ptrs; > + const void *block; > void *ptrs_block; > > + /* > + * The hardcoded fp_timing_size is only valid for > + * modernish VBTs. All older VBTs definitely should > + * include block 41 and thus we don't need to > + * generate one. > + */ > + if (i915->vbt.version < 155) > + return NULL; > + > + fp_timing_size = 38; > + > block = find_raw_section(bdb, BDB_LVDS_LFP_DATA); > if (!block) > return NULL; > @@ -385,17 +384,8 @@ static void *generate_lfp_data_ptrs(struct drm_i915_private *i915, > > block_size = get_blocksize(block); > > - size = block_size; > - t0 = find_fp_timing_terminator(block, size); > - if (!t0) > - return NULL; > - > - size -= t0 - block - 2; > - t1 = find_fp_timing_terminator(t0 + 2, size); > - if (!t1) > - return NULL; > - > - size = t1 - t0; > + size = fp_timing_size + sizeof(struct lvds_dvo_timing) + > + sizeof(struct lvds_pnp_id); > if (size * 16 > block_size) > return NULL; > > @@ -413,7 +403,7 @@ static void *generate_lfp_data_ptrs(struct drm_i915_private *i915, > table_size = sizeof(struct lvds_dvo_timing); > size = make_lfp_data_ptr(&ptrs->ptr[0].dvo_timing, table_size, size); > > - table_size = t0 - block + 2; > + table_size = fp_timing_size; > size = make_lfp_data_ptr(&ptrs->ptr[0].fp_timing, table_size, size); > > if (ptrs->ptr[0].fp_timing.table_size) > @@ -428,14 +418,14 @@ static void *generate_lfp_data_ptrs(struct drm_i915_private *i915, > return NULL; > } > > - size = t1 - t0; > + size = fp_timing_size + sizeof(struct lvds_dvo_timing) + > + sizeof(struct lvds_pnp_id); > for (i = 1; i < 16; i++) { > next_lfp_data_ptr(&ptrs->ptr[i].fp_timing, &ptrs->ptr[i-1].fp_timing, size); > next_lfp_data_ptr(&ptrs->ptr[i].dvo_timing, &ptrs->ptr[i-1].dvo_timing, size); > next_lfp_data_ptr(&ptrs->ptr[i].panel_pnp_id, &ptrs->ptr[i-1].panel_pnp_id, size); > } > > - size = t1 - t0; > table_size = sizeof(struct lvds_lfp_panel_name); > > if (16 * (size + table_size) <= block_size) { -- Jani Nikula, Intel Open Source Graphics Center
