quoted

Anyway, one thing I mentioned earlier was that we could solve the
problem of drivers accessing unmapped IO ports and crashing systems on
archs which define PCI_IOBASE by building them under some "native port
IO support" flag.

Right, that was part of the goal here.

Great

quoted

One example of such a driver was F71805F sensor. You put that under
HAS_IOPORT, which would be available for all archs, I think. But I could
not see where config LEGACY_PCI is introduced. Could we further refine
that config to not build for such archs as arm64?

BTW, I think that the PPC dependency was added there to stop building
for power for that same reason, so hopefully we get rid of that.

Good point. It seems that I actually never added the LEGACY_PCI option
to my patch,

ok, it would be nice to see that.

so I'm just not building those drivers any more, and not
defining the inb()/outb() helpers either, causing a build failure when I'm
missing an option.

However it sounds like you are interested in a third option here, which
brings us to:

LEGACY_PCI: any PCI driver that uses inb()/outb() or is only available
     on old-style PCI but not PCIe hardware without a bridge.
     To be disabled for most architectures and possibly distros but can
     be enabled for kernels that want to use those devices, as long as
     CONFIG_HAS_IOPORT is set by the architecture.

HAS_IOPORT: not a legacy PCI device, but can only be built on
     architectures that define inb()/outb(). To be disabled for s390
     and any other machine that has no useful definition of those
     functions.

That seems reasonable. And asm-generic io.h should be ifdef'ed by 
HAS_IOPORT. In your patch you had it under CONFIG_IOPORT - was that 
intentional?

On another point, I noticed SCSI driver AHA152x depends on ISA, but is 
not an isa driver - however it does use port IO. Would such dependencies 
need to be changed to depend on HAS_IOPORT?

I did notice that arm32 support CONFIG_ISA - not sure why.

HARDCODED_IOPORT: (or another name you might think of,) Used by
    drivers that unconditionally do inb()/outb() without checking the
    validity of the address using firmware or other methods first.
    depends on HAS_IOPORT and possibly architecture specific
    settings.

Yeah, that sounds the same as what I was thinking. Maybe IOPORT_NATIVE 
could work as a name. I would think that only x86/ia64 would define it. 
A concern though is that someone could argue that is a functional 
dependency, rather than just a build dependency.

Thanks,
John