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diff --git a/documentation/content/en/books/handbook/config/_index.adoc b/documentation/content/en/books/handbook/config/_index.adoc
--- a/documentation/content/en/books/handbook/config/_index.adoc
+++ b/documentation/content/en/books/handbook/config/_index.adoc
@@ -1347,6 +1347,21 @@
ACPI can be used to put the system into a sleep mode with `acpiconf`, the `-s` flag, and a number from `1` to `5`. Most users only need `1` (quick suspend to RAM) or `3` (suspend to RAM). Option `5` performs a soft-off which is the same as running `halt -p`.
+The man:acpi_video[4] driver uses
+link:https://uefi.org/specs/ACPI/6.4/Apx_B_Video_Extensions/Apx_B_Video_Extensions.html[ACPI
+Video Extensions] to control display switching and backlight brightness. It must
+be loaded after any of the DRM kernel modules. After loading the driver,
+the kbd:[Fn] brightness keys will change the brightness of the screen. It is
+possible to check the ACPI events by inspecting [.filename]#/var/run/devd.pipe#:
+
+[source,shell]
+...
+# cat /var/run/devd.pipe
+!system=ACPI subsystem=Video type=brightness notify=62
+!system=ACPI subsystem=Video type=brightness notify=63
+!system=ACPI subsystem=Video type=brightness notify=64
+...
+
Other options are available using `sysctl`. Refer to man:acpi[4] and man:acpiconf[8] for more information.
[[ACPI-comprob]]

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