On Tue, Mar 22, 2022 at 11:40:34PM +0200, Jani Nikula wrote:
> Add an iterator for CEA Data Blocks across CEA extensions and CTA
> DisplayID Data Blocks.
>
> Signed-off-by: Jani Nikula <jani.nik...@intel.com>
> ---
> drivers/gpu/drm/drm_edid.c | 198 ++++++++++++++++++++++++++++++++++---
> 1 file changed, 186 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 31d132fcd0ca..c12c3cbab274 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -4196,24 +4196,12 @@ do_hdmi_vsdb_modes(struct drm_connector *connector,
> const u8 *db, u8 len,
> return modes;
> }
>
> -static int
> -cea_db_payload_len(const u8 *db)
> -{
> - return db[0] & 0x1f;
> -}
> -
> static int
> cea_db_extended_tag(const u8 *db)
> {
> return db[1];
> }
>
> -static int
> -cea_db_tag(const u8 *db)
> -{
> - return db[0] >> 5;
> -}
> -
> static int
> cea_revision(const u8 *cea)
> {
> @@ -4269,6 +4257,192 @@ cea_db_offsets(const u8 *cea, int *start, int *end)
> return 0;
> }
>
> +/*
> + * CEA Data Block iterator.
> + *
> + * Iterate through all CEA Data Blocks in both EDID CEA extensions and CTA
> Data
> + * Blocks in DisplayID extension blocks.
> + *
> + * struct cea_db *db:
> + * struct cea_db_iter iter;
> + *
> + * cea_db_iter_edid_begin(edid, &iter);
> + * cea_db_iter_for_each(db, &iter) {
> + * // do stuff with db
> + * }
> + * cea_db_iter_end(&iter);
> + */
> +struct cea_db_iter {
> + struct drm_edid_iter edid_iter;
> + struct displayid_iter displayid_iter;
> +
> + /* Current Data Block Collection. */
> + const u8 *collection;
> +
> + /* Current Data Block index in current collection. */
> + int index;
> +
> + /* End index in current collection. */
> + int end;
> +};
> +
> +/* CEA-861-F section 7.5 CEA Extension Version 3 and Table 43 */
> +struct cea_db {
> + u8 tag_length;
> + u8 data[];
> +} __packed;
> +
> +static int cea_db_tag(const void *_db)
> +{
> + /* FIXME: Transition to passing struct cea_db * everywhere. */
> + const struct cea_db *db = _db;
> +
> + return db->tag_length >> 5;
> +}
> +
> +static int cea_db_payload_len(const void *_db)
> +{
> + /* FIXME: Transition to passing struct cea_db * everywhere. */
> + const struct cea_db *db = _db;
> +
> + return db->tag_length & 0x1f;
> +}
> +
> +static const void *cea_db_data(const struct cea_db *db)
> +{
> + return db->data;
> +}
> +
> +static void cea_db_iter_edid_begin(const struct edid *edid, struct
> cea_db_iter *iter)
> +{
> + memset(iter, 0, sizeof(*iter));
> +
> + drm_edid_iter_begin(edid, &iter->edid_iter);
> + displayid_iter_edid_begin(edid, &iter->displayid_iter);
> +}
> +
> +static const struct cea_db *
> +__cea_db_iter_current_block(const struct cea_db_iter *iter)
> +{
> + const struct cea_db *db;
> +
> + if (!iter->collection)
> + return NULL;
> +
> + db = (const struct cea_db *)&iter->collection[iter->index];
> +
> + if (iter->index + sizeof(*db) <= iter->end &&
> + iter->index + sizeof(*db) + cea_db_payload_len(db) <= iter->end)
> + return db;
> +
> + return NULL;
> +}
> +
> +/*
> + * References:
> + * - VESA E-EDID v1.4
> + * - CEA-861-F section 7.5 CEA Extension Version 3
> + */
> +static const void *__cea_db_iter_edid_next(struct cea_db_iter *iter)
> +{
> + const u8 *ext;
> +
> + drm_edid_iter_for_each(ext, &iter->edid_iter) {
> + /* Only support CEA extension revision 3+ */
> + if (ext[0] != CEA_EXT || cea_revision(ext) < 3)
> + continue;
> +
> + iter->index = 4;
> + iter->end = ext[2];
> + if (iter->end == 0)
> + iter->end = 127;
> + if (iter->end < 4 || iter->end > 127)
> + continue;
> +
> + return ext;
> + }
> +
> + return NULL;
> +}
> +
> +/*
> + * References:
> + * - DisplayID v1.3 Appendix C: CEA Data Block within a DisplayID Data Block
> + * - DisplayID v2.0 section 4.10 CTA DisplayID Data Block
> + *
> + * Note that the above do not specify any connection between DisplayID Data
> + * Block revision and CEA Extension versions.
> + */
> +static const void *__cea_db_iter_displayid_next(struct cea_db_iter *iter)
> +{
> + const struct displayid_block *block;
> +
> + displayid_iter_for_each(block, &iter->displayid_iter) {
> + if (block->tag != DATA_BLOCK_CTA)
> + continue;
> +
> + iter->index = sizeof(*block);
> + iter->end = iter->index + block->num_bytes;
I'd like to keep the comment from cea_db_offsets() reminding
us why we can trust this thing.
Overall looks pretty nice to my eyes.
Reviewed-by: Ville Syrjälä <ville.syrj...@linux.intel.com>
> +
> + return block;
> + }
> +
> + return NULL;
> +}
> +
> +static const struct cea_db *__cea_db_iter_next(struct cea_db_iter *iter)
> +{
> + const struct cea_db *db;
> +
> + if (iter->collection) {
> + /* Current collection should always be valid. */
> + db = __cea_db_iter_current_block(iter);
> + if (WARN_ON(!db)) {
> + iter->collection = NULL;
> + return NULL;
> + }
> +
> + /* Next block in CEA Data Block Collection */
> + iter->index += sizeof(*db) + cea_db_payload_len(db);
> +
> + db = __cea_db_iter_current_block(iter);
> + if (db)
> + return db;
> + }
> +
> + for (;;) {
> + /*
> + * Find the next CEA Data Block Collection. First iterate all
> + * the EDID CEA extensions, then all the DisplayID CTA blocks.
> + *
> + * Per DisplayID v1.3 Appendix B: DisplayID as an EDID
> + * Extension, it's recommended that DisplayID extensions are
> + * exposed after all of the CEA extensions.
> + */
> + iter->collection = __cea_db_iter_edid_next(iter);
> + if (!iter->collection)
> + iter->collection = __cea_db_iter_displayid_next(iter);
> +
> + if (!iter->collection)
> + return NULL;
> +
> + db = __cea_db_iter_current_block(iter);
> + if (db)
> + return db;
> + }
> +}
> +
> +#define cea_db_iter_for_each(__db, __iter) \
> + while (((__db) = __cea_db_iter_next(__iter)))
> +
> +static void cea_db_iter_end(struct cea_db_iter *iter)
> +{
> + displayid_iter_end(&iter->displayid_iter);
> + drm_edid_iter_end(&iter->edid_iter);
> +
> + memset(iter, 0, sizeof(*iter));
> +}
> +
> static bool cea_db_is_hdmi_vsdb(const u8 *db)
> {
> if (cea_db_tag(db) != CEA_DB_VENDOR)
> --
> 2.30.2
--
Ville Syrjälä
Intel
