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[NOTE] [NOTE]
==== ====
ACPI and APM cannot coexist and should be used separately. The last one to load will terminate if the driver notices the other is running. ACPI and APM cannot coexist and should be used separately. The last one to load will terminate if the driver notices the other is running.
==== ====
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`. 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. Other options are available using `sysctl`. Refer to man:acpi[4] and man:acpiconf[8] for more information.
[[ACPI-comprob]] [[ACPI-comprob]]
=== Common Problems === Common Problems
ACPI is present in all modern computers that conform to the ia32 (x86) and amd64 (AMD) architectures. The full standard has many features including CPU performance management, power planes control, thermal zones, various battery systems, embedded controllers, and bus enumeration. Most systems implement less than the full standard. For instance, a desktop system usually only implements bus enumeration while a laptop might have cooling and battery management support as well. Laptops also have suspend and resume, with their own associated complexity. ACPI is present in all modern computers that conform to the ia32 (x86) and amd64 (AMD) architectures. The full standard has many features including CPU performance management, power planes control, thermal zones, various battery systems, embedded controllers, and bus enumeration. Most systems implement less than the full standard. For instance, a desktop system usually only implements bus enumeration while a laptop might have cooling and battery management support as well. Laptops also have suspend and resume, with their own associated complexity.
An ACPI-compliant system has various components. The BIOS and chipset vendors provide various fixed tables, such as FADT, in memory that specify things like the APIC map (used for SMP), config registers, and simple configuration values. Additionally, a bytecode table, the Differentiated System Description Table DSDT, specifies a tree-like name space of devices and methods. An ACPI-compliant system has various components. The BIOS and chipset vendors provide various fixed tables, such as FADT, in memory that specify things like the APIC map (used for SMP), config registers, and simple configuration values. Additionally, a bytecode table, the Differentiated System Description Table DSDT, specifies a tree-like name space of devices and methods.
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