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Re: [Qemu-devel] [PATCH v3 1/8] hw/arm/virt: Add a GPIO controller

From: Shannon Zhao
Subject: Re: [Qemu-devel] [PATCH v3 1/8] hw/arm/virt: Add a GPIO controller
Date: Tue, 01 Dec 2015 23:25:02 +0800
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0

On 2015/12/1 22:48, Pavel Fedin wrote:

ACPI 5.0 supports GPIO-signaled ACPI Events. This can be used for
powerdown, hotplug evnets. Add a GPIO controller in machine virt,

to support powerdown, maybe can be used for cpu hotplug. And
here we use pl061.

  Sorry for late jumping in, but this was the first message Cc'ed to me.
  With these devices virt machine IMHO goes farther and farther away from its 
initial goal: be a minimalistic virtual box, which ensures maximum possible 
compatibility and portability.
  virt machine already supports poweroff using PSCI interface. Why we need to 
add more hardware? Can't ACPI deal with PSCI?
Hi Pavel,

IIUC, the poweroff using PSCI interface is the guest *internal* poweroff, that is you type "poweroff" inside guest. But this patch set is going to introduce a way to support *external* poweroff, like the power button on our desktop. This is something like you push a button to shutdown the guest.

  To tell the truth, i dislike ACPI + EFI thing at all. It looks like cramming 
PC-oriented firmware into architecture for which it was never meant to be 
written. Too much overcomplications, we drop already established things and 
reinvent a (triangular) wheel, but what's the purpose? Is it being done only 
because vendors want obscure proprietary firmware instead of old good u-boot?

Kind regards,
Pavel Fedin
Expert Engineer
Samsung Electronics Research center Russia


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