Messages in this thread | | | Date | Wed, 26 Mar 2008 22:07:38 +0000 | From | Alan Cox <> | Subject | Re: [patch] pci: revert "PCI: remove transparent bridge sizing" |
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> 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
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