1In the good old days when graphics parameters were configured explicitly 2in a file called xorg.conf, even broken hardware could be managed. 3 4Today, with the advent of Kernel Mode Setting, a graphics board is 5either correctly working because all components follow the standards - 6or the computer is unusable, because the screen remains dark after 7booting or it displays the wrong area. Cases when this happens are: 8- The graphics board does not recognize the monitor. 9- The graphics board is unable to detect any EDID data. 10- The graphics board incorrectly forwards EDID data to the driver. 11- The monitor sends no or bogus EDID data. 12- A KVM sends its own EDID data instead of querying the connected monitor. 13Adding the kernel parameter "nomodeset" helps in most cases, but causes 14restrictions later on. 15 16As a remedy for such situations, the kernel configuration item 17CONFIG_DRM_LOAD_EDID_FIRMWARE was introduced. It allows to provide an 18individually prepared or corrected EDID data set in the /lib/firmware 19directory from where it is loaded via the firmware interface. The code 20(see drivers/gpu/drm/drm_edid_load.c) contains built-in data sets for 21commonly used screen resolutions (1024x768, 1280x1024, 1680x1050, 221920x1080) as binary blobs, but the kernel source tree does not contain 23code to create these data. In order to elucidate the origin of the 24built-in binary EDID blobs and to facilitate the creation of individual 25data for a specific misbehaving monitor, commented sources and a 26Makefile environment are given here. 27 28To create binary EDID and C source code files from the existing data 29material, simply type "make". 30 31If you want to create your own EDID file, copy the file 1024x768.S and 32replace the settings with your own data. The CRC value in the last line 33 #define CRC 0x55 34is a bit tricky. After a first version of the binary data set is 35created, it must be be checked with the "edid-decode" utility which will 36most probably complain about a wrong CRC. Fortunately, the utility also 37displays the correct CRC which must then be inserted into the source 38file. After the make procedure is repeated, the EDID data set is ready 39to be used. 40