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The flags used to determine which devices could be plugged into which controllers were quite confusing, as they tried to create classes of connections, then put particular devices into possibly multiple classes, while sometimes setting multiple flags for the controllers themselves. The attempt to have a single flag indicate, e.g. that a root-port or a switch-downstream-port could connect was not only confusing, it was leading to a situation where it would be impossible to specify exactly the right combinations for a new controller. The solution is for the VIR_PCI_CONNECT_TYPE_* flags to have a 1:1 correspondence with each type of PCI controller, plus a flag for a PCI endpoint device and another for a PCIe endpoint device (the only exception to this is that pci-bridge and pcie-expander-bus controllers have their upstream connection classified as VIR_PCI_CONNECT_TYPE_PCI_DEVICE since they can be plugged into *exactly* the same ports as any endpoint device). Each device then has a single flag for connect type (plus the HOTPLUG flag if that device can e hotplugged), and each controller sets the CONNECT bits for all controllers that can be plugged into it, as well as for either type of endpoint device that can be plugged in (and the HOTPLUG flag if it can accept hotplugged devices). With this change, it is *slightly* easier to understand the matching of connections (as long as you remember that the flag for a device/upstream-facing connection of a controller is the same as that device's type, while the flags for a controller's downstream connections is the OR of all device types that can be plugged into that controller). More importantly, it will be possible to correctly specify what can be plugged into a pcie-switch-expander-bus, when support for it is added.
LibVirt : simple API for virtualization
Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.
Daniel Veillard <veillard@redhat.com>