[RFC PATCH 1/6] ad9389b: verify EDID header

[Hans Verkuil]

From: Mats Randgaard <matra...@cisco.com>

Ignore EDIDs where the header is wrong.

Signed-off-by: Mats Randgaard <matra...@cisco.com>
Signed-off-by: Hans Verkuil <hans.verk...@cisco.com>
---
 drivers/media/i2c/ad9389b.c | 26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/drivers/media/i2c/ad9389b.c b/drivers/media/i2c/ad9389b.c
index b06a7e5..e7f7171 100644
--- a/drivers/media/i2c/ad9389b.c
+++ b/drivers/media/i2c/ad9389b.c
@@ -978,7 +978,7 @@ static bool edid_block_verify_crc(u8 *edid_block)
        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 ad9389b_state *state = get_ad9389b_state(sd);
        u32 blocks = state->edid.blocks;
@@ -992,6 +992,25 @@ static bool edid_segment_verify_crc(struct v4l2_subdev 
*sd, u32 segment)
        return false;
 }
 
+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 ad9389b_state *state = get_ad9389b_state(sd);
+       u8 *data = state->edid.data;
+       int i;
+
+       if (segment)
+               return true;
+
+       for (i = 0; i < ARRAY_SIZE(hdmi_header); i++)
+               if (data[i] != hdmi_header[i])
+                       return false;
+
+       return true;
+}
+
 static bool ad9389b_check_edid_status(struct v4l2_subdev *sd)
 {
        struct ad9389b_state *state = get_ad9389b_state(sd);
@@ -1019,9 +1038,10 @@ static bool ad9389b_check_edid_status(struct v4l2_subdev 
*sd)
                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_err(sd, "%s: edid crc error\n", __func__);
+               v4l2_err(sd, "%s: edid crc or header error\n", __func__);
                state->have_monitor = false;
                ad9389b_s_power(sd, false);
                ad9389b_s_power(sd, true);
-- 
1.8.4.rc3

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