Messages in this thread | | | Date | Mon, 6 Sep 2004 02:40:58 +0100 | From | Matthew Wilcox <> | Subject | Re: multi-domain PCI and sysfs |
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On Sun, Sep 05, 2004 at 07:50:04PM -0400, Jon Smirl wrote: > So how do multiple root buses work? Since they are all in the same > domain it seems like a single IO operation would go to all of the root > bridges simultaneously. Then each root bridge matches to the address > and decides to send the IO operation on if there is a match.
Not exactly -- each rope (the line that connects the memory & I/O controller to the I/O adapter) has a limited bandwidth, so the memory & I/O controller makes the decision which rope each transaction is destined for.
> When implementing the VGA control I'm running into the problem that > there is no root node in sysfs for the top of a domain. I need a > domain node to attach an attribute disabling all VGA devices in the > domain. In the zx1 diagram I could have vga devices on any of the > PCI-X or AGP buses.
Why would it be a problem if the attribute is per-bus, as it is right now? see bus->bridge_ctl (PCI_BRIDGE_CTL_VGA)
> With the xz1 sysfs would look like this: > /sys/devices/pci0000:00 > /sys/devices/pci0000:01 > /sys/devices/pci0000:02 > /sys/devices/pci0000:03 > /sys/devices/pci0000:04 > /sys/devices/pci0000:05
Actually, they're sparsely numbered to allow for people plugging in pci-pci bridges on cards, so:
$ ls -1 /sys/devices/ pci0000:00 pci0000:80 pci0000:a0 pci0000:c0 platform system
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