Re: [Qemu-discuss] Guidance requested creating a QEMU MMIO device

[Peter Maydell]

On Tue, 16 Apr 2019 at 14:18, <address@hidden> wrote:
>
> Thanks, Peter.
>
> I can see how to use parts of the mps2-scc code to set up my wanted MMIO.
> I would basically need an array of 32-bit words and would not need to 
> differentiate
> between control and data registers. That's what I hope at least.
>
> You wrote;
>
> > You would then need to modify the board code for whatever
> > machine you're trying to use this with to create the device
> > at whatever physical address you want it to live at.
>
> You didn't specify what you meant by 'board code'. Since a qemu is supposed 
> to emulate a
> specific processor/cpu, e.g. an arm cortex-a53 or a ppc mpc8544ds.

The board code is the code that models a particular board or
machine (which you specify on the command line with -M machinename).
It's under hw/${ARCH}/, usually, eg the versatilepb and versatileab
boards are handled by hw/arm/versatilepb.c.

For mps2-scc, you can see where the device is created by
looking for TYPE_MPS2_SCC -- it's used in the boards
modelled in hw/arm/mps2-tz.c and hw/arm/mps2.c.

All that code in roms/ that you found is just the source
code for a copy of u-boot which we ship as a ROM blob
to run on certain guest boards -- it is irrelevant to you.

thanks
-- PMM