Re: [patch] pci: revert "PCI: remove transparent bridge sizing"

[Alan Cox]

> PCI bridges at zero is perfectly valid indeed and I'm sure we have that
> around at least for IO space. In fact, I'm surprised you don't have that
> on x86. Typically, things like an HT segment with a P2P bridge and
> behind that bridge an ISA bridge could well have the P2P bridge with a
> resource forwarding 0...0x1000 IO downstream for example even on x86
> no ? (I'm not -that- familiar with the crazyness of legacy ISA on x86
> but I've definitely seen such setup on other archs).

On a PC system 0x00-0xFF are motherboard resources (sometimes chipset,
some even swallowed by the CPU in certain cases) so 0 as disabled is sort
of safe but as shown by the pci_enable_device_bars replacement code - not
a good idea neccessarily.

A lot of driver code does assume 0 == unavailable/off/disabled including
large chunks of serial, ata, ide and probably other subsystems.

Alan
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/