On Wed, Jan 30, 2013 at 4:47 AM, Thomas Petazzoni
[off-list ref] wrote:

So what I'm going to do now is rework my patch series by removing the
emulated host bridge (which is normally mandatory by PCIe standard, but
Linux doesn't need it, so we don't care), ...

This is a tangent since you're removing the emulated host bridge
anyway, but it's been mentioned a couple of times, and I'd like to
understand this.  Jason mentioned earlier in the [07/27] emulated host
bridge thread that the PCIe spec requires a host bridge at 00:00.0.
I've never seen that mentioned in the spec; can somebody point me to
the actual requirement that host bridges appear in config space?

My understanding has been that host bridges, whether PCI or PCIe, are
required to *exist*, but that the way you enumerate them and configure
them is outside the scope of the PCI/PCIe specs.  I know that many
chips, especially for x86, *do* make the host bridge appear in config
space, but I've never seen a requirement for that.

Bjorn