Re: [Qemu-devel] [PATCH 4/5] PPC: e500: Support platform devices

[Alexander Graf <agraf@suse.de>]

On 19.06.14 16:56, Eric Auger wrote:
> On 06/04/2014 02:28 PM, Alexander Graf wrote:
>> For e500 our approach to supporting platform devices is to create a simple
>> bus from the guest's point of view within which we map platform devices
>> dynamically.
>>
>> We allocate memory regions always within the "platform" hole in address
>> space and map IRQs to predetermined IRQ lines that are reserved for platform
>> device usage.
>>
>> This maps really nicely into device tree logic, so we can just tell the
>> guest about our virtual simple bus in device tree as well.
> Hi Alex,
>
> this "qemu_add_machine_init_done_notifier" was the qemu mechanism I
> missed in my patch. You light my way ;-)
>
> One first comment is it would make much sense to reuse your code in arm
> virt.c too. I am currently doing the exercise. Do you think it would be
> possible to share a common helper code, outside of e500 machine code?

Yes, definitely :). I was mostly doing it in e500.c as a starting point. 
The second implementation (virt.c apparently) would then go in and 
commonalize everything it thinks should be common.

I'm not 100% sure where the right line is here though. For the 
implementation today I just throw everything into a new virtual platform 
bus for the guest. But there's no reason I couldn't detect "this is the 
first UART in my system" and put it in place where the real first UART 
would be in CCSR.

So yeah, again, I'm not 100% sure where the right line of distinction 
between board specific and generic code is here :).


Alex