[gl-como] Differenza ACPI/UDEV

Davide De Prisco deprisco.davide@gmail.com
Ven 4 Maggio 2018 13:03:04 CEST

Cercando di configurare bene il mio Thinkpad e la sua docking station
mi si è palesato un quesito che pare di poco conto ma è di
fondamentale importanza nell'approccio a questo tipo di problema.
"Ma che cacchio di differenza c'è tra ACPI e UDEV? Cosa devo
configurare per modificare il comportamento del mio piccì quando
attacco o stacco qualcosa?"

Cercando nel www ho trovato questa risposta che ora condivido con voi
perché dopo averla letta mi sono sentito meno stupido (di poco)
"... ACPI is a low-level interface for mainboard vendors to provide
information about built-in devices that cannot be (reliably)
autodetected to the operating system. It also provides methods for
power management and hardware monitoring to the kernel. One
interesting thing ACPI provides are so called ACPI events. To create
these, the hardware emits a special interrupt (the General Purpose
Event Interrupt) when something happens on built in hardware and the
kernel then calls the ACPI code which determines what happened on
which built-in device. See the specification if you want to know how
the whole thing works in detail.

acpid is a daemon that listens for the events generated by the ACPI
subsystem in the kernel and allows to run commands when a specific
event happened. For example if the hardware signaled via ACPI that the
power button was pressed, you get an event on a device in the
"button/power" class. The daemon can only react to these events
generated via ACPI and not to events on e.g. the USB bus.

udev is a Linux-specific daemon that allows to react on changes in the
device tree managed by the kernel. For example if you plug in an USB
stick, the kernel is notified by the USB controller and a new device
is added to the Linux device tree. Then the usb_storage driver detects
that the new device is a storage device and creates sub-device nodes
in the tree that allow the user space to handle the USB stick like any
other hard drive. If you plug it out, these devices are removed from
the tree. udev is notified on each of these additions and removals.
udev can also react to some events that aren't device
additions/removals like opening/closing of a CD tray, but that's most
of it. You can run udevadm monitor --kernel to see what events udev
gets in real time.

You can say that acpid and udev complement each other. udev is useful
to react to major changes about any device the OS knows about, while
acpid is useful to react to more specific events that happen to some
built-in devices....."

Tratto dal yahoo answer del Linux

E da questa definizione pare che sia UDEV da configurare



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