Re: [Qemu-arm] [Qemu-devel] [PATCH] microbit: make -kernel optional

[Stefan Hajnoczi]

On Thu, Jan 3, 2019 at 1:07 PM Peter Maydell <address@hidden> wrote:
> On Fri, 14 Dec 2018 at 14:51, Stefan Hajnoczi <address@hidden> wrote:
> > ARMv7M machine types support -kernel for ELF and raw image files.
> > Microbit programs are typically in Intel HEX (.hex) format.  The generic
> > loader supports .hex files but it doesn't work as expected:
> >
> >   $ qemu-system-arm -M microbit -device loader,file=microbit.hex
> >   Guest image must be specified (using -kernel)
> >
> > This error comes from armv7m_load_kernel() but we don't have -kernel in
> > this case.
> >
> > This patch makes -kernel optional since most of the time we'll want to
> > use -device loader instead.
> >
> > Note that we need to register the reset handler that
> > armv7m_load_kernel() used to register for us.
> >
> > Signed-off-by: Stefan Hajnoczi <address@hidden>
>
> Hi, Stefan. (Happy new year :-))
>
> Looking at this, I think I'd prefer it if we handled
> this in the armv7m_load_kernel() code, since having to register
> your own reset handler to reset the CPU is a weird thing for
> board level code to have to do. That then means the M-profile
> kernel load code is in line with the A-profile load code, which
> if it has no kernel to load will still register the reset handler,
> and let the machine run however it ends up running.
>
> I think this basically amounts to "remove the 'insist that
> kernel_filename is not NULL' check from armv7m_load_kernel()",
> aka "revert commit 01fd41ab3fb69971". That commit's commit
> message is correct that the behaviour if the user didn't
> specify anything to run is a bit unhelpful, but it predates
> the generic loader so it's no longer necessarily true that
> a kernel must be specified, either for this or for any other
> M-profile machine. (There's also the case of "board has a
> flash device that was populated via a -pflash or -drive
> option".)

Happy New Year!

That makes sense.  I will send a patch.

Stefan