Re: [PATCH] Add a comment about endian-ness of capabilities recorded in pci config space

[Michael S. Tsirkin]

On Mon, Oct 25, 2021 at 03:47:36PM +0530, Ani Sinha wrote:
> Values in PCI configuration space are written in little endian format. This
> includes capability values recorded in pci config space for pci bridges etc.
> Add comment to remind developers to make sure the values are written in little
> endian for all platforms and that the code must be endian safe.
> Please also see the following fix which resolves an issue related to code not
> being endian safe for BE systems:

drop an empty line here maybe

> 
> 0e464f7d99311 ("pci: fix PCI resource reserve capability on BE")
> Signed-off-by: Ani Sinha <ani@anisinha.ca>

If we are doing this, I think the correct approach is
to start adding __bitwise__ annotations and fix up
make sparse so we can have endian-ness automatically checked.


> ---
>  include/hw/pci/pci_bridge.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/include/hw/pci/pci_bridge.h b/include/hw/pci/pci_bridge.h
> index a94d350034..5fc6841833 100644
> --- a/include/hw/pci/pci_bridge.h
> +++ b/include/hw/pci/pci_bridge.h
> @@ -143,6 +143,8 @@ typedef struct PCIBridgeQemuCap {
>  /*
>   * PCI BUS/IO/MEM/PREFMEM additional resources recorded as a
>   * capability in PCI configuration space to reserve on firmware init.
> + * The values of these parameters must be in little-endian and
> + * the code assigning the values must be endian safe for all platforms.
>   */
>  typedef struct PCIResReserve {
>      uint32_t bus;
> -- 
> 2.25.1