Re: [Qemu-devel] [PATCH][RFC 0/14] implement power chip

[Peter Maydell]

On 19 March 2013 00:55, li guang <address@hidden> wrote:
> 在 2013-03-18一的 11:07 +0000，Peter Maydell写道：
>> I'm really dubious that this can or should be implemented by
>> adding methods at the device base class level. I don't think
>> real hardware works this way.
>
> and what it should be?
>
>>  You could probably do power on/off
>> like this. Reset definitely shouldn't be done this way, and
>> suspend probably not either.
>
> AFAIK, reset is mostly power off then power on,

The DeviceState method 'reset' simulates a power cycle.
On real hardware power-controller controlled reset is
more complicated and generally devices implement one
or more reset pins which can be asserted by the power
controller.

> suspend, of course is not supported by all devices,
> but, if system want to suspend, it have to let all devices
> aware this, and if the device support power suspend, it
> can do something specific(or just some with others, simple)

I suspect this should involve more modelling of actual
control signals between the power controller and
the devices, not methods on the base class.

> I'm eager to get more comments and discussion.
> This idea simply based on system board design convention,
> I'm not saying a power chip has signals directly connected
> to all devices, I mean system board and its devices should
> have protocol to deal with power state changes.

Hardware does it with signals, so should we.

-- PMM