EDID

In the good old days when graphics parameters were configured explicitly in a file called xorg.conf, even broken hardware could be managed.

Today, with the advent of Kernel Mode Setting, a graphics board is either correctly working because all components follow the standards - or the computer is unusable, because the screen remains dark after booting or it displays the wrong area. Cases when this happens are:

• The graphics board does not recognize the monitor.

• The graphics board is unable to detect any EDID data.

• The graphics board incorrectly forwards EDID data to the driver.

• The monitor sends no or bogus EDID data.

• A KVM sends its own EDID data instead of querying the connected monitor.

Adding the kernel parameter “nomodeset” helps in most cases, but causes restrictions later on.

As a remedy for such situations, the kernel configuration item CONFIG_DRM_LOAD_EDID_FIRMWARE was introduced. It allows to provide an individually prepared or corrected EDID data set in the /lib/firmware directory from where it is loaded via the firmware interface.