Re: [PATCH v10 01/17] pci: msi: pass pdev to pci_enable_msi() function

["Roger Pau Monné" <roger.pau@citrix.com>]

On Thu, Oct 12, 2023 at 10:09:14PM +0000, Volodymyr Babchuk wrote:
> Previously pci_enable_msi() function obtained pdev pointer by itself,
> but taking into account upcoming changes to PCI locking, it is better
> when caller passes already acquired pdev pointer to the function.

A bit more detail into why this matters for the upcoming locking
change would be useful here.

> Note that ns16550 driver does not check validity of obtained pdev
> pointer because pci_enable_msi() already does this.
> 
> Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@epam.com>
> 
> ---
> Changes in v10:
> 
>  - New in v10. This is the result of discussion in "vpci: add initial
>  support for virtual PCI bus topology"
> ---
>  xen/arch/x86/include/asm/msi.h |  3 ++-
>  xen/arch/x86/irq.c             |  2 +-
>  xen/arch/x86/msi.c             | 19 ++++++++++---------
>  xen/drivers/char/ns16550.c     |  4 +++-
>  4 files changed, 16 insertions(+), 12 deletions(-)
> 
> diff --git a/xen/arch/x86/include/asm/msi.h b/xen/arch/x86/include/asm/msi.h
> index a53ade95c9..836c8cd4ba 100644
> --- a/xen/arch/x86/include/asm/msi.h
> +++ b/xen/arch/x86/include/asm/msi.h
> @@ -81,7 +81,8 @@ struct irq_desc;
>  struct hw_interrupt_type;
>  struct msi_desc;
>  /* Helper functions */
> -extern int pci_enable_msi(struct msi_info *msi, struct msi_desc **desc);
> +extern int pci_enable_msi(struct msi_info *msi, struct msi_desc **desc,
> +			  struct pci_dev *pdev);

Hard tabs (here and below).

I agree with Jan that it might be better for pdev to be the first
parameter.

Otherwise seems fine if the pdev is already in the caller context, as
we avoid an extra list walk.

Thanks, Roger.