Re: [Qemu-devel] [RFC PATCH v2 3/4] pci: add QEMU-specific PCI capability structure

[Michael S. Tsirkin]

On Sun, Jul 23, 2017 at 01:11:49AM +0300, Aleksandr Bezzubikov wrote:
> On PCI init PCI bridge devices may need some
> extra info about bus number to reserve, IO, memory and
> prefetchable memory limits. QEMU can provide this
> with special vendor-specific PCI capability.
> 
> This capability is intended to be used only
> for Red Hat PCI bridges, i.e. QEMU cooperation.
> 
> Sizes of limits match ones from 
> PCI Type 1 Configuration Space Header,
> number of buses to reserve occupies only 1 byte 
> since it is the size of Subordinate Bus Number register.
> 
> Signed-off-by: Aleksandr Bezzubikov <address@hidden>
> ---
>  src/hw/pci_cap.h | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
>  create mode 100644 src/hw/pci_cap.h
> 
> diff --git a/src/hw/pci_cap.h b/src/hw/pci_cap.h
> new file mode 100644
> index 0000000..1382b0b
> --- /dev/null
> +++ b/src/hw/pci_cap.h
> @@ -0,0 +1,23 @@
> +#ifndef _PCI_CAP_H
> +#define _PCI_CAP_H
> +
> +#include "types.h"
> +
> +struct vendor_pci_cap {
> +    u8 id;
> +    u8 next;
> +    u8 len;
> +};
> +
> +struct redhat_pci_bridge_cap {
> +    struct vendor_pci_cap hdr;

You want to add some kind of identifier here after
the header, such that more capabilities can be added
in future without breaking this one.

> +    u8 bus_res;
> +    u32 pref_lim_upper;
> +    u16 pref_lim;
> +    u16 mem_lim;
> +    u16 io_lim_upper;
> +    u8 io_lim;
> +    u8 padd;

Please add documentation.


> +};
> +
> +#endif /* _PCI_CAP_H */
> -- 
> 2.7.4