media: cec: make cec_get_edid_spa_location() an inline function

[mirror_ubuntu-bionic-kernel.git] / include / media / cec.h

diff --git a/include/media/cec.h b/include/media/cec.h
index 16341210d3ba10e34ec02e7fd458e3b7f25b8d48..a60fed96b2d61a252e5d1b2fa80f26d071a75dcd 100644 (file)
--- a/include/media/cec.h
+++ b/include/media/cec.h
@@ -449,4 +449,74 @@ static inline void cec_phys_addr_invalidate(struct cec_adapter *adap)
        cec_s_phys_addr(adap, CEC_PHYS_ADDR_INVALID, false);
 }
 
+/**
+ * cec_get_edid_spa_location() - find location of the Source Physical Address
+ *
+ * @edid: the EDID
+ * @size: the size of the EDID
+ *
+ * This EDID is expected to be a CEA-861 compliant, which means that there are
+ * at least two blocks and one or more of the extensions blocks are CEA-861
+ * blocks.
+ *
+ * The returned location is guaranteed to be <= size-2.
+ *
+ * This is an inline function since it is used by both CEC and V4L2.
+ * Ideally this would go in a module shared by both, but it is overkill to do
+ * that for just a single function.
+ */
+static inline unsigned int cec_get_edid_spa_location(const u8 *edid,
+                                                    unsigned int size)
+{
+       unsigned int blocks = size / 128;
+       unsigned int block;
+       u8 d;
+
+       /* Sanity check: at least 2 blocks and a multiple of the block size */
+       if (blocks < 2 || size % 128)
+               return 0;
+
+       /*
+        * If there are fewer extension blocks than the size, then update
+        * 'blocks'. It is allowed to have more extension blocks than the size,
+        * since some hardware can only read e.g. 256 bytes of the EDID, even
+        * though more blocks are present. The first CEA-861 extension block
+        * should normally be in block 1 anyway.
+        */
+       if (edid[0x7e] + 1 < blocks)
+               blocks = edid[0x7e] + 1;
+
+       for (block = 1; block < blocks; block++) {
+               unsigned int offset = block * 128;
+
+               /* Skip any non-CEA-861 extension blocks */
+               if (edid[offset] != 0x02 || edid[offset + 1] != 0x03)
+                       continue;
+
+               /* search Vendor Specific Data Block (tag 3) */
+               d = edid[offset + 2] & 0x7f;
+               /* Check if there are Data Blocks */
+               if (d <= 4)
+                       continue;
+               if (d > 4) {
+                       unsigned int i = offset + 4;
+                       unsigned int end = offset + d;
+
+                       /* Note: 'end' is always < 'size' */
+                       do {
+                               u8 tag = edid[i] >> 5;
+                               u8 len = edid[i] & 0x1f;
+
+                               if (tag == 3 && len >= 5 && i + len <= end &&
+                                   edid[i + 1] == 0x03 &&
+                                   edid[i + 2] == 0x0c &&
+                                   edid[i + 3] == 0x00)
+                                       return i + 4;
+                               i += len + 1;
+                       } while (i < end);
+               }
+       }
+       return 0;
+}
+
 #endif /* _MEDIA_CEC_H */