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Date: Tue, 11 Jun 2013 07:33:02 +0200
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] qemu: piix: PCI bridge ACPI hotplug support
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>, Anthony Liguori <anthony@codemonkey.ws>, David Woodhouse <dwmw2@infradead.org>, seabios@seabios.org, qemu-devel@nongnu.org, Kevin O'Connor <kevin@koconnor.net>, Jordan Justen <jljusten@gmail.com>, Laszlo Ersek <lersek@redhat.com>

  Hi,

>        * Use of glib's GArray makes it much easier to build
>          up tables in code without need for iasl and code patching

Nice.

> Design:
>     - each bus gets assigned a number 0-255
>     - generated ACPI code writes this number
>       to a new BSEL register, then uses existing
>       UP/DOWN registers to probe slot status;
>       to eject, write number to BSEL register,
>       then slot into existing EJ
> 
>     This is to address the ACPI spec requirement to
>     avoid config cycle access to any bus except PCI roots.
> 
> Portability:
>     - Non x86 (or any Linux) platforms don't need any of this code.
>       They can keep happily using SHPC the way
>       they always did.

Hmm.  Is is possible to write a SHPC driver in AML?  I think it would be
alot better to have one guest/host interface for pci bridge hotplug
instead of two.

cheers,
  Gerd