Re: [Qemu-devel] [PATCH] turn firmware image filename into a machine option

[Peter Maydell]

On 1 October 2013 20:22, Gerd Hoffmann <address@hidden> wrote:
> On Di, 2013-10-01 at 19:55 +0900, Peter Maydell wrote:
>> No documentation or definition of what the semantics of
>> specifying a "firmware image" filename are?
>
> "-machine firmware=$file" has the same effect as "-bios $file", which is
> simliar to '-machine kernel=$file' and '-kernel $file'.

It's similar in that it has semantics that might vary between target cpu
architecture or even between target machines, and which aren't
very well documented... -bios we're stuck with because it's a legacy
option, but if we're going to change/augment the syntax here it
would be good to be sure that we end up with something that's
(a) consistent across boards/architectures (b) not going to turn
into another awkward legacy option.

>> Why is this a machine option rather than a property of
>> the ROM/flash device?
>
> Not all machines have a flash device.

No, but they must have *something* that the firmware code lives in...

> Also flash drives don't want a
> simple (readonly) image file but a (writable) blockdev as backing
> storage, at least the pflash device emulation I've briefly looked at.

...so how does this work for machines where the firmware lives in
a flash device? Does -firmware=foo override setting the backing
image for the flash device, or vice versa, or do machines with flash
devices not support -firmware=foo, or something else?

-- PMM