Re: [Qemu-devel] [PATCH v4 3/9] target-avr: adding a sample AVR board

[Peter Maydell <peter.maydell@linaro.org>]

On 5 July 2016 at 23:22, Michael Rolnik <mrolnik@gmail.com> wrote:
> Peter,
>
> I do not understand this comment
>
> Exactly one of these memory regions (your main "RAM") should be
> allocated via memory_region_allocate_system_memory()
> [which does the vmstate_register_ram_global() for that MR].
> The idea is that every board has one-and-only-one main RAM MR.
> (We should have a memory_region_allocate_aux_memory()
> as the parallel API to save you having to do the vmstate_register_ram_global
> yourself for the other two, but currently we don't.)
>
> could you please point me to an example/documentation.

See for instance hw/arm/vexpress.c. We call
memory_region_allocate_system_memory() only once,
for the main RAM. The little bit of RAM "vexpress.a15sram"
is not allocated with that function.

> as for this one
>
> This isn't very descriptive; a short phrase which gives users
> a clue about whether they want to use this board would be good.
>
> currently I am concerned with CPU and not with boards/devices/models.
> I hope, once there is AVR CPU, some people (including me) will join and
> create real boards, this one is just a sample. it does not do any real
> stuff. it allows to load a simple program and run.
> If I start to design a real board/model now it will take me some time and
> during this time no one is going to use/profit from AVR CPU in QEMU.
> that's why it's called sample.

Unfortunately it's not quite that simple. Once code goes into
QEMU, we have to maintain it, and we need to continue
to support users who have started using it. That means that
we could easily still have this "sample" board around in five
years time. So you need to get it at least basically right and
useful from the beginning.

My point about the better descriptive phrase is that this
is user-facing documentation (it appears in "-M help" output
where we list all the supported boards). "sample" on its
own doesn't do much to help users or suggest to them or
remind them what this board model is.

thanks
-- PMM