drm/edid: add HF-EEODB support to EDID read and allocation

HDMI 2.1 section 10.3.6 defines an HDMI Forum EDID Extension Override
Data Block, which may contain a different extension count than the base
block claims. Add support for reading more EDID data if available. The
extra blocks aren't parsed yet, though.

Hard-coding the EEODB parsing instead of using the iterators we have is
a bit of a bummer, but we have to be able to do this on a partially
allocated EDID while reading it.

v2:
- Check for CEA Data Block Collection size (Ville)
- Amend commit message and comment about hard-coded parsing

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/57b57a355d62eb91ad1e3cf555978576f2bd9fdd.1656494768.git.jani.nikula@intel.com

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index a80ea0a..fa3a3e2 100644 (file)
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -1581,6 +1581,15 @@ static bool version_greater(const struct drm_edid *drm_edid,
                (edid->version == version && edid->revision > revision);
 }
 
+static int edid_hfeeodb_extension_block_count(const struct edid *edid);
+
+static int edid_hfeeodb_block_count(const struct edid *edid)
+{
+       int eeodb = edid_hfeeodb_extension_block_count(edid);
+
+       return eeodb ? eeodb + 1 : 0;
+}
+
 static int edid_extension_block_count(const struct edid *edid)
 {
        return edid->extensions;
@@ -2026,6 +2035,11 @@ static struct edid *edid_filter_invalid_blocks(struct edid *edid,
        struct edid *new;
        int i, valid_blocks = 0;
 
+       /*
+        * Note: If the EDID uses HF-EEODB, but has invalid blocks, we'll revert
+        * back to regular extension count here. We don't want to start
+        * modifying the HF-EEODB extension too.
+        */
        for (i = 0; i < edid_block_count(edid); i++) {
                const void *src_block = edid_block_data(edid, i);
 
@@ -2261,7 +2275,7 @@ static struct edid *_drm_do_get_edid(struct drm_connector *connector,
                                     size_t *size)
 {
        enum edid_block_status status;
-       int i, invalid_blocks = 0;
+       int i, num_blocks, invalid_blocks = 0;
        struct edid *edid, *new;
        size_t alloc_size = EDID_LENGTH;
 
@@ -2303,7 +2317,8 @@ static struct edid *_drm_do_get_edid(struct drm_connector *connector,
                goto fail;
        edid = new;
 
-       for (i = 1; i < edid_block_count(edid); i++) {
+       num_blocks = edid_block_count(edid);
+       for (i = 1; i < num_blocks; i++) {
                void *block = (void *)edid_block_data(edid, i);
 
                status = edid_block_read(block, i, read_block, context);
@@ -2314,11 +2329,31 @@ static struct edid *_drm_do_get_edid(struct drm_connector *connector,
                        if (status == EDID_BLOCK_READ_FAIL)
                                goto fail;
                        invalid_blocks++;
+               } else if (i == 1) {
+                       /*
+                        * If the first EDID extension is a CTA extension, and
+                        * the first Data Block is HF-EEODB, override the
+                        * extension block count.
+                        *
+                        * Note: HF-EEODB could specify a smaller extension
+                        * count too, but we can't risk allocating a smaller
+                        * amount.
+                        */
+                       int eeodb = edid_hfeeodb_block_count(edid);
+
+                       if (eeodb > num_blocks) {
+                               num_blocks = eeodb;
+                               alloc_size = edid_size_by_blocks(num_blocks);
+                               new = krealloc(edid, alloc_size, GFP_KERNEL);
+                               if (!new)
+                                       goto fail;
+                               edid = new;
+                       }
                }
        }
 
        if (invalid_blocks) {
-               connector_bad_edid(connector, edid, edid_block_count(edid));
+               connector_bad_edid(connector, edid, num_blocks);
 
                edid = edid_filter_invalid_blocks(edid, &alloc_size);
        }
@@ -3851,6 +3886,7 @@ static int add_detailed_modes(struct drm_connector *connector,
 #define CTA_EXT_DB_HDR_STATIC_METADATA 6
 #define CTA_EXT_DB_420_VIDEO_DATA      14
 #define CTA_EXT_DB_420_VIDEO_CAP_MAP   15
+#define CTA_EXT_DB_HF_EEODB            0x78
 #define CTA_EXT_DB_HF_SCDB             0x79
 
 #define EDID_BASIC_AUDIO       (1 << 6)
@@ -4910,6 +4946,12 @@ static bool cea_db_is_hdmi_forum_vsdb(const struct cea_db *db)
                cea_db_payload_len(db) >= 7;
 }
 
+static bool cea_db_is_hdmi_forum_eeodb(const void *db)
+{
+       return cea_db_is_extended_tag(db, CTA_EXT_DB_HF_EEODB) &&
+               cea_db_payload_len(db) >= 2;
+}
+
 static bool cea_db_is_microsoft_vsdb(const struct cea_db *db)
 {
        return cea_db_is_vendor(db, MICROSOFT_IEEE_OUI) &&
@@ -4944,6 +4986,47 @@ static bool cea_db_is_hdmi_hdr_metadata_block(const struct cea_db *db)
                cea_db_payload_len(db) >= 3;
 }
 
+/*
+ * Get the HF-EEODB override extension block count from EDID.
+ *
+ * The passed in EDID may be partially read, as long as it has at least two
+ * blocks (base block and one extension block) if EDID extension count is > 0.
+ *
+ * Note that this is *not* how you should parse CTA Data Blocks in general; this
+ * is only to handle partially read EDIDs. Normally, use the CTA Data Block
+ * iterators instead.
+ *
+ * References:
+ * - HDMI 2.1 section 10.3.6 HDMI Forum EDID Extension Override Data Block
+ */
+static int edid_hfeeodb_extension_block_count(const struct edid *edid)
+{
+       const u8 *cta;
+
+       /* No extensions according to base block, no HF-EEODB. */
+       if (!edid_extension_block_count(edid))
+               return 0;
+
+       /* HF-EEODB is always in the first EDID extension block only */
+       cta = edid_extension_block_data(edid, 0);
+       if (edid_block_tag(cta) != CEA_EXT || cea_revision(cta) < 3)
+               return 0;
+
+       /* Need to have the data block collection, and at least 3 bytes. */
+       if (cea_db_collection_size(cta) < 3)
+               return 0;
+
+       /*
+        * Sinks that include the HF-EEODB in their E-EDID shall include one and
+        * only one instance of the HF-EEODB in the E-EDID, occupying bytes 4
+        * through 6 of Block 1 of the E-EDID.
+        */
+       if (!cea_db_is_hdmi_forum_eeodb(&cta[4]))
+               return 0;
+
+       return cta[4 + 2];
+}
+
 static void drm_parse_y420cmdb_bitmap(struct drm_connector *connector,
                                      const u8 *db)
 {