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-rw-r--r--include/media/cec.h70
1 files changed, 70 insertions, 0 deletions
diff --git a/include/media/cec.h b/include/media/cec.h
index ff9847f7f99d..603f2fa08f62 100644
--- a/include/media/cec.h
+++ b/include/media/cec.h
@@ -461,4 +461,74 @@ 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 */