Re: [PATCH v3 21/33] lance: replace PROP_PTR with PROP_LINK

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

On Thu, 24 Oct 2019 at 12:48, Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
> Just wondering, if we had a "bus_address" property to the abstract
> SysBus class (and eventually "bus_name" for later) we could create/map
> sysbus devices from command line?

I don't think this is a good plan -- users shouldn't have to know
about the memory map of their boards. Plus it doesn't deal with
the complications of multiple address spaces, DMA, wiring up
irq lines to an interrupt controller, SoC reset handling,
clocks, power-managment...  Command line -device was designed
for pluggable devices, where in the world of real hardware
the device can be physically plugged and unplugged and there's
a clear interface that can be modelled. You can't add an
extra UART to an embedded board in real hardware either.

The only plausible argument I've seen for command-line
plugging of embedded devices is as a sort of side-effect
of having a configuration language syntax for them for
the purpose of being able to write board models as
data-driven config files rather than in C code. But
that would be a lot of design and engineering work, and
if we want that I think we should approach it forwards,
not arrive at it backwards by adding gradual tweaks like
'address' properties to devices.

thanks
-- PMM