On Wed, Dec 07, 2022 at 07:25:49AM +0100, Markus Armbruster wrote: > 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?
I'm ok with pci_defs.h However, I note that most headers including pci.h don't really need it. Consider include/hw/virtio/virtio-iommu.h all it needs is PCIBus typedef this is available from qemu/typedefs.h So if you are poking at this, want to clean that area up generally? > 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