Re: [Qemu-devel] [PATCH 0/4] add ACPI Embedded Controller

[li guang <lig.fnst@cn.fujitsu.com>]

在 2013-05-26日的 19:51 -0500，Anthony Liguori写道：
> li guang <lig.fnst@cn.fujitsu.com> writes:
> 
> > 在 2013-05-24五的 14:45 +0300，Michael S. Tsirkin写道：
> >> On Wed, May 22, 2013 at 11:46:33AM +0800, liguang wrote:
> >> > These patches try to add ACPI Embedded Controller (EC),
> >> > refer-to:
> >> > ACPI SPEC v5 chapter 5 
> >> > "ACPI Embedded Controller Interface Specification"
> >> > 
> >> > EC is a standard ACPI device, it plays flexible roles,
> >> > e.g. 
> >> > power controller, it can control power sequence for
> >> > platform to enter or leave system state(0,1,3,4,5),
> >> > it can controller CPU fan by the temperature of sensor.
> >> > event carrier, it can pass events between platform
> >> > and OS, so OS can execute _Qxx method which defined
> >> > by yourself.
> >> > 
> >> > So, I want to deliver CPU online/offline event between
> >> > OS and QEMU for CPU hotplug feature, then we will don't
> >> > need to "echo 1 > /sys/devices/system/cpu/cpu1/online"
> >> > again after 'cpu-add'.
> >> > 
> >> > patches for online/offline event handler of QEUM and 
> >> > linux kernel are writing, and will send once finished.
> >> > 
> >> > since EC is a common device, so I send pathes separately.
> >> 
> >> Do any non-linux guests support this device?
> >> 
> >
> > In fact, any OSes support ACPI will support this device.
> > so, windows will.
> 
> When you say "any OSes supporting ACPI" I think what you really mean is
> that we can provide bytecode that interacts with the embedded
> controller.
> 
> There is not explicit driver in Linux or Windows AFAIK.

Hmm, yep, mostly there's no special driver for EC,
because it is directly embedded in code for ACPI
for linux kernel, it's drivers/acpi/ec.c

> 
> I still don't get the point of this.  We can make ACPI hotplug work
> without introducing a new device like this.
> 

when you 'cpu-add' a cpu, acpi driver for cpu will not
trigger 'cpu_up' for linux kernel AFAIK, unless you add
a user space program to listen it's uevent and tigger 'cpu_up'.

and EC is not only for ACPI hotplug
for example, the 'pvpanic', if there's a EC,
we can pass pvpanic event by EC's ACPI space or Q-event,
then we will not need this kind of special devices anymore.