Disclaimer: Try the following at your own risk, it may brick your TV/monitor

My TV set (an "old" LG 32LG5000 model) never played well with Linux. Whenever I connected to it via an HDMI port, the kernel would complain:

kernel: [ 869.677850] [drm:drm_edid_block_valid] *ERROR* EDI has major version 2, instead of 1

and then would completely ignore the TV.

Because I didn't use it all that much anyway (and the VGA still worked, although at 1360x768), I hadn't really bothered to find out what was wrong. Today however, I wanted to watch a movie and the laptop's VGA output quality really sucked, so I decided to have a look and see if I could get things to work.

Analyzing the EDID For those unfamiliar with the terms, the EDID is a small piece of data that encodes a monitor's capabilities, most notably the resolutions and timings it supports, allowing zero-configuration use of monitors. The above error is particularly interesting, in that there (almost) never was a version 2.0 EDID: according to Wikipedia, EDID structure versions range from v1.0 to v1.4; all these define upwards-compatible 128-byte structures. EDID structure v2.0 defined a new 256-byte structure, but subsequently has been deprecated and replaced by v1.3. It seems that EDID 2.0 was deprecated around 2000, and it's funny that a TV set manufactured in 2008 reports this version. After googling a bit, I found some sporadic references that this model was erroneously labeled as having a version 2.0 EDID, while in fact its EDID was 1.3. I tried a firmware update to the latest version, but it didn't fix the issue, so at this point I had 2 options: Patch the kernel and remove the major version check. This was ugly, plus I would have to compile at least the drm module every time I upgraded my kernel. Patch the EDID and try to get either the TV or the kernel to use it. Feeling a bit adventurous, I opted for the latter. Loading the i2c-dev module gives us access to the raw EDID data, using get-edid (part of the read-edid package in Debian): # get-edid > /tmp/edid.bin This is read-edid version 3.0.1. Prepare for some fun. Attempting to use i2c interface No EDID on bus 0 No EDID on bus 1 No EDID on bus 2 No EDID on bus 4 No EDID on bus 5 No EDID on bus 7 2 potential busses found: 3 6 Will scan through until the first EDID is found. Pass a bus number as an option to this program to go only for that one. 256-byte EDID successfully retrieved from i2c bus 3 Looks like i2c was successful. Have a good day. Note that we got the EDID from i2c bus 3. Let's see now what's in there: # parse-edid < /tmp/edid.bin Checksum Correct Section "Monitor" Identifier "32LG5000" ModelName "32LG5000" VendorName "GSM" # Monitor Manufactured week 9 of 2008 # EDID version 2.0 # Digital Display DisplaySize 700 390 Gamma 2.20 Option "DPMS" "true" Horizsync 28-67 VertRefresh 50-75 # Maximum pixel clock is 150MHz #Not giving standard mode: 640x480, 60Hz #Not giving standard mode: 800x600, 60Hz #Not giving standard mode: 1024x768, 60Hz #Not giving standard mode: 1920x1080, 60Hz #Extension block found. Parsing... Modeline "Mode 16" +hsync +vsync Modeline "Mode 0" -hsync -vsync Modeline "Mode 1" -hsync +vsync Modeline "Mode 2" 27.027 720 736 798 858 480 489 495 525 -hsync -vsync Modeline "Mode 3" 27.000 720 732 796 864 576 581 586 625 -hsync -vsync Modeline "Mode 4" 25.200 640 656 752 800 480 490 492 525 -hsync -vsync Modeline "Mode 5" 27.027 720 736 798 858 480 489 495 525 -hsync -vsync Modeline "Mode 6" 27.000 720 732 796 864 576 581 586 625 -hsync -vsync Modeline "Mode 7" 74.250 1280 1720 1760 1980 720 725 730 750 +hsync +vsync Modeline "Mode 8" 74.250 1280 1390 1420 1650 720 725 730 750 +hsync +vsync Modeline "Mode 9" 74.250 1920 2448 2492 2640 1080 1082 1089 1125 +hsync +vsync interlace Modeline "Mode 10" 74.250 1920 2008 2052 2200 1080 1082 1087 1125 +hsync +vsync interlace Modeline "Mode 11" 74.250 1920 2448 2492 2640 1080 1084 1089 1125 +hsync +vsync Modeline "Mode 12" 148.500 1920 2448 2492 2640 1080 1084 1089 1125 +hsync +vsync Modeline "Mode 13" 74.250 1920 2558 2602 2750 1080 1084 1089 1125 +hsync +vsync Modeline "Mode 14" 74.250 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync Modeline "Mode 15" 148.500 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync Modeline "Mode 17" +hsync +vsync Modeline "Mode 18" +hsync +vsync interlace Modeline "Mode 19" -hsync -vsync Option "PreferredMode" "Mode 16" EndSection The model name confirms we have the right EDID. Note the # EDID version 2.0 string that parse-edid reports, which agrees with what the kernel complains about. Also note that parse-edid found an extension block as well, one specifying the timings and resolutions supported by the TV. Let's have a look at the raw data now: # hd /tmp/edid.bin 00000000 00 ff ff ff ff ff ff 00 1e 6d f0 75 01 01 01 01 |.........m.u....| 00000010 09 12 02 00 80 46 27 78 ea d9 b0 a3 57 49 9c 25 |.....F'x....WI.%| 00000020 11 49 4b a5 6e 00 31 40 45 40 61 40 d1 c0 01 01 |.IK.n.1@E@a@....| 00000030 01 01 01 01 01 01 26 36 80 a0 70 38 1f 40 50 20 |......&6..p8.@P | 00000040 85 00 bc 86 21 00 00 18 1b 21 50 a0 51 00 1e 30 |....!....!P.Q..0| 00000050 48 88 35 00 bc 86 21 00 00 1c 00 00 00 fc 00 33 |H.5...!........3| 00000060 32 4c 47 35 30 30 30 0a 20 20 20 20 00 00 00 fd |2LG5000. ....| 00000070 00 32 4b 1c 43 0f 00 0a 20 20 20 20 20 20 01 f9 |.2K.C... ..| 00000080 02 03 21 f1 4e 02 11 01 03 12 13 04 14 05 21 1f |..!.N.........!.| 00000090 20 22 10 23 09 07 07 83 01 00 00 65 03 0c 00 30 | ".#.......e...0| 000000a0 00 01 1d 00 bc 52 d0 1e 20 b8 28 55 40 c4 8e 21 |.....R.. .(U@..!| 000000b0 00 00 1e 01 1d 00 72 51 d0 1e 20 6e 28 55 00 c4 |......rQ.. n(U..| 000000c0 8e 21 00 00 1e 01 1d 80 d0 72 1c 16 20 10 2c 25 |.!.......r.. .,%| 000000d0 80 c4 8e 21 00 00 9e 8c 0a d0 90 20 40 31 20 0c |...!....... @1 .| 000000e0 40 55 00 c4 8e 21 00 00 18 4e 1f 00 80 51 00 1e |@U...!...N...Q..| 000000f0 30 40 80 37 00 bc 88 21 00 00 18 00 00 00 00 ac |0@.7...!........| 00000100 The raw EDID data comprises two sections, 128 bytes each (remember, this is an EDID 1.3 blob, incorrectly labeled as 2.0). The first section is the main one and the second one is the extension, an EIA/CEA-861 extension block containing the native resolutions and timings. Using the Wikipedia article as a reference, we quickly find out that bytes 0x12 and 0x13 are the EDID version (with values 0x02 and 0x00 in our case) and the checksum byte 0xf7 (with a value of 0xf9 ).