1 .. SPDX-License-Identifier: GPL-2.0 1 .. SPDX-License-Identifier: GPL-2.0
2 2
3 ==== 3 ====
4 EDID 4 EDID
5 ==== 5 ====
6 6
7 In the good old days when graphics parameters 7 In the good old days when graphics parameters were configured explicitly
8 in a file called xorg.conf, even broken hardwa 8 in a file called xorg.conf, even broken hardware could be managed.
9 9
10 Today, with the advent of Kernel Mode Setting, 10 Today, with the advent of Kernel Mode Setting, a graphics board is
11 either correctly working because all component 11 either correctly working because all components follow the standards -
12 or the computer is unusable, because the scree 12 or the computer is unusable, because the screen remains dark after
13 booting or it displays the wrong area. Cases w 13 booting or it displays the wrong area. Cases when this happens are:
14 14
15 - The graphics board does not recognize the mo 15 - The graphics board does not recognize the monitor.
16 - The graphics board is unable to detect any E 16 - The graphics board is unable to detect any EDID data.
17 - The graphics board incorrectly forwards EDID 17 - The graphics board incorrectly forwards EDID data to the driver.
18 - The monitor sends no or bogus EDID data. 18 - The monitor sends no or bogus EDID data.
19 - A KVM sends its own EDID data instead of que 19 - A KVM sends its own EDID data instead of querying the connected monitor.
20 20
21 Adding the kernel parameter "nomodeset" helps 21 Adding the kernel parameter "nomodeset" helps in most cases, but causes
22 restrictions later on. 22 restrictions later on.
23 23
24 As a remedy for such situations, the kernel co 24 As a remedy for such situations, the kernel configuration item
25 CONFIG_DRM_LOAD_EDID_FIRMWARE was introduced. 25 CONFIG_DRM_LOAD_EDID_FIRMWARE was introduced. It allows to provide an
26 individually prepared or corrected EDID data s 26 individually prepared or corrected EDID data set in the /lib/firmware
27 directory from where it is loaded via the firm 27 directory from where it is loaded via the firmware interface.
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