[RFC PATCH 7/6] adv7511: verify EDID header

[Hans Verkuil]

Ignore EDID's where the header is wrong.

Signed-off-by: Martin Bugge <marbu...@cisco.com>
Signed-off-by: Hans Verkuil <hans.verk...@cisco.com>
---
 drivers/media/i2c/adv7511.c | 35 ++++++++++++++++++++++++-----------
 1 file changed, 24 insertions(+), 11 deletions(-)

diff --git a/drivers/media/i2c/adv7511.c b/drivers/media/i2c/adv7511.c
index f20450c..ee61894 100644
--- a/drivers/media/i2c/adv7511.c
+++ b/drivers/media/i2c/adv7511.c
@@ -965,26 +965,38 @@ static void adv7511_check_monitor_present_status(struct 
v4l2_subdev *sd)
 
 static bool edid_block_verify_crc(uint8_t *edid_block)
 {
-       int i;
        uint8_t sum = 0;
+       int i;
 
        for (i = 0; i < 128; i++)
-               sum += *(edid_block + i);
-       return (sum == 0);
+               sum += edid_block[i];
+       return sum == 0;
 }
 
-static bool edid_segment_verify_crc(struct v4l2_subdev *sd, u32 segment)
+static bool edid_verify_crc(struct v4l2_subdev *sd, u32 segment)
 {
        struct adv7511_state *state = get_adv7511_state(sd);
        u32 blocks = state->edid.blocks;
        uint8_t *data = state->edid.data;
 
-       if (edid_block_verify_crc(&data[segment * 256])) {
-               if ((segment + 1) * 2 <= blocks)
-                       return edid_block_verify_crc(&data[segment * 256 + 
128]);
+       if (!edid_block_verify_crc(&data[segment * 256]))
+               return false;
+       if ((segment + 1) * 2 <= blocks)
+               return edid_block_verify_crc(&data[segment * 256 + 128]);
+       return true;
+}
+
+static bool edid_verify_header(struct v4l2_subdev *sd, u32 segment)
+{
+       static const u8 hdmi_header[] = {
+               0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00
+       };
+       struct adv7511_state *state = get_adv7511_state(sd);
+       u8 *data = state->edid.data;
+
+       if (segment != 0)
                return true;
-       }
-       return false;
+       return !memcmp(data, hdmi_header, sizeof(hdmi_header));
 }
 
 static bool adv7511_check_edid_status(struct v4l2_subdev *sd)
@@ -1013,9 +1025,10 @@ static bool adv7511_check_edid_status(struct v4l2_subdev 
*sd)
                        state->edid.blocks = state->edid.data[0x7e] + 1;
                        v4l2_dbg(1, debug, sd, "%s: %d blocks in total\n", 
__func__, state->edid.blocks);
                }
-               if (!edid_segment_verify_crc(sd, segment)) {
+               if (!edid_verify_crc(sd, segment) ||
+                   !edid_verify_header(sd, segment)) {
                        /* edid crc error, force reread of edid segment */
-                       v4l2_dbg(1, debug, sd, "%s: edid crc error\n", 
__func__);
+                       v4l2_err(sd, "%s: edid crc or header error\n", 
__func__);
                        state->have_monitor = false;
                        adv7511_s_power(sd, false);
                        adv7511_s_power(sd, true);
-- 
1.8.4.rc3

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