On 24/01/2023 00:13, BALATON Zoltan wrote:
On Mon, 23 Jan 2023, Mark Cave-Ayland wrote:
On 22/01/2023 22:16, BALATON Zoltan wrote:
The problem you are ultimately trying to solve though is that OpenBIOS is loading
the NDRV for all VGA PCI devices, so why not just fix drivers/vga.fs so that the
NDRV is loaded only for the QEMU VGA device?
So this patch neither adds new dependency to QEMU nor repends on any change in
OpenBIOS. It just gets rid of passing files via fw_cfg.
Unfortunately that still doesn't solve the problem of building a self-contained
OpenBIOS ROM, so this patch isn't the right way forward.
It does take a step to make it possible to eventually add a self contained ROM and
remove the vga.fs from OpenBIOS but it's not doing that fully. It just simplifies
QEMU and OpenBIOS vga.fs for now and making the ROM also contain the FCode will be
a further step but we can't get there if you don't allow to make smaller steps or
don't merge my patches for OpenBIOS which would allow it to run FCode ROMs. If
you're waiting for all this to be finished I'll give up and it will never be
finished. If you allow to progress in smaller steps then maybe we'll get there.
You can already add a self-contained rom using the romfile= property, so that's not
preventing you from doing anything though? Even once OpenBIOS can
Except that OpenBIOS will break the device tree by adding the qemu_vga.ndrv to the
video card node so the card rom I pass via romfile will see it's already there and
won't install its owm. Then MacOS will try to use the wrong driver and it does not
work and I spend a lot of time to find out I also need -prom env vga-ndrv?=false to
avoid this problem which I always forget and somebody trying this for the first time
won't even know.
What's more, all this complication is not needed. With this patch everything works as
before for std VGA as it will have the qemu_vga.ndrv as its romfile but ati-vga won't
so OpenBIOS only installs it for std VGA without adding anything to OpenBIOS to
handle this. Adding a romfile to ati-vga will work without further hassle and the
romfile option can also be used to replace or disable the qemu_vga.ndrv for std VGA
as -device VGA,romdile="" (or add your FCode in development here). Due to the way
standard VGA works adding -device VGA,romfile= to the command line won't add a second
VGA device just set the option for the default one (actually it omits the default and
adds the specified one but the point is this just works).
Then we not only not need to add anythig to OpenBIOS but we can drop the vga-ndrv?
option (which does not exist on real machines anyway) and also all the code in vga.fs
to get the driver from fw_cfg so simplifying it leaving only the code which will
eventually need to be part of the FCode ROM. Once this patch is accepted it fixes the
above problem and allows to simplify OpenBIOS later and when we're there you just
have to replace qemu_vga.ndrv with the version that prepends the FCode from vga.fs
before it so I don't see what's your problem with this patch. Can you give a reason
why it can't be accepted?
It doesn't work this way though: once the FCode ROM is working it also generates the
QEMU,VGA device tree node, which means that -device VGA,romfile="" will not only
disable qemu_vga.ndrv, but also leave a device node missing the properties required
for the guest to correctly identify the VGA adapter.
As I already mentioned, this is the wrong approach and what is needed is to fix
vga.fs in OpenBIOS so that the NDRV is only loaded for the QEMU,VGA device.
read PCI option ROMs, the option ROM will still need to contain OpenBIOS's vga.fs
as a payload, and it will still need to be able to inject qemu_vga.ndrv because
OpenBIOS cannot have an external dependency upon QemuMacDrivers.
The way real card ROMs work is that they embed the driver binary and have some FCode
that adds that to the device tree. It should be the same for QEMU emulated cards so
if you say that you want only vga.fs as the card ROM which then downloads the
qemu_vga.ndrv from QEMU that makes no sense at all. Currently the qemu_vga.ndrv is
build from QemuMacDrivers and added as a binary to QEMU. You can add it as a binary
the same way to OpenBIOS then build the FCOde ROM from vga.fs and qemu_vga.ndrv bin
that results in the FCode ROM that will replace qemu_vga.ndrv binaty in QEMU. You
just say this is not possible because you're OK with adding the qemu_vga,ndrv binary
to QEMU but doing the same with OpenBIOS cannot be done?
What you're suggesting doesn't make any sense, as all you're doing is moving the
binary from QEMU where there is already precedent for distributing binary ROMs to
OpenBIOS where it becomes a build dependency that cannot be built outside of a very
specific guest environment.
I should also add that it wasn't me who designed and implemented the existing scheme
for keeping the qemu_vga.ndrv binary in QEMU, it was Ben - and his approach still
seems to be the best solution in my opinion.
ATB,
Mark.
