Re: How to best make include/hw/pci/pcie_sriov.h self-contained

[Philippe Mathieu-Daudé]

On 7/12/22 07:25, 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?

Sounds good to me. Eventually name it pci_standard_defs.h?

We can move the first 100 lines of pci.h there, PCI_ROM_SLOT, 
PCI_NUM_REGIONS, PCI HEADER_TYPE, PCI_NUM_PINS, cap_present, and 
eventually PCIINTxRoute & PCIReqIDType.

> 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.fsf@blackfin.pond.sub.org>
>      https://lists.nongnu.org/archive/html/qemu-devel/2016-03/msg03345.html