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