pcie_sriov.h needs PCI_NUM_REGIONS from pci.h, but doesn't include it. pci.h must be included before pcie_sriov.h or else compile fails.
Adding #include "pci/pci.h" to pcie_sriov would be wrong, because it would close an inclusion loop: pci.h includes pcie.h (for PCIExpressDevice) includes pcie_sriov.h (for PCIESriovPF) includes pci.h (for PCI_NUM_REGIONS). The obvious solution is to move PCI_NUM_REGIONS pci.h somewhere pcie_sriov.h can include without creating a loop. We already have a few headers that don't include anything: pci_ids.h, pci_regs.h (includes include/standard-headers/linux/pci_regs.h, which doesn't count), pcie_regs.h. Moving PCI_NUM_REGIONS to one of these would work, but it doesn't feel right. We could create a new one, say pci_defs.h. Just for PCI_NUM_REGIONS feels silly. So, what else should move there? Any other ideas? In case you wonder why I bother you with this... Back in 2016, we discussed[1] rules for headers, and these were generally liked: 1. Have a carefully curated header that's included everywhere first. We got that already thanks to Peter: osdep.h. 2. Headers should normally include everything they need beyond osdep.h. If exceptions are needed for some reason, they must be documented in the header. If all that's needed from a header is typedefs, put those into qemu/typedefs.h instead of including the header. 3. Cyclic inclusion is forbidden. I'm working on patches to get include/ closer to obeying 2. [1] Message-ID: <87h9g8j57d....@blackfin.pond.sub.org> https://lists.nongnu.org/archive/html/qemu-devel/2016-03/msg03345.html