Re: [PATCH v11 3/5] PCI/TPH: Add pcie_tph_enabled_mode() helper

[Alex Williamson <alex@shazbot.org>]

On Fri, 22 May 2026 17:18:39 +0800
fengchengwen <fengchengwen@huawei.com> wrote:

> On 5/22/2026 12:10 PM, Alex Williamson wrote:
> > On Mon, 18 May 2026 15:16:59 +0800
> > Chengwen Feng <fengchengwen@huawei.com> wrote:
> >   
> >> Add a helper to query enabled TPH mode on a PCI device. This is useful for
> >> drivers like VFIO-PCI that need to validate TPH state before allowing
> >> access to steering tag tables.
> >>
> >> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
> >> ---
> >>  drivers/pci/tph.c       | 12 ++++++++++++
> >>  include/linux/pci-tph.h |  3 +++
> >>  2 files changed, 15 insertions(+)
> >>
> >> diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c
> >> index ba31b010f67a..91c1e83410a3 100644
> >> --- a/drivers/pci/tph.c
> >> +++ b/drivers/pci/tph.c
> >> @@ -451,6 +451,18 @@ int pcie_enable_tph(struct pci_dev *pdev, int mode)
> >>  }
> >>  EXPORT_SYMBOL(pcie_enable_tph);
> >>  
> >> +/**
> >> + * pcie_tph_enabled_mode - Get current enabled TPH mode
> >> + * @pdev: PCI device
> >> + *
> >> + * Return the enabled TPH mode (IV/DS) or 0 if disabled.
> >> + */
> >> +int pcie_tph_enabled_mode(struct pci_dev *pdev)
> >> +{
> >> +	return pdev->tph_enabled ? pdev->tph_mode : 0;
> >> +}
> >> +EXPORT_SYMBOL(pcie_tph_enabled_mode);  
> > 
> > Doesn't this create ambiguity with PCI_TPH_ST_NS_MODE?  Maybe return an
> > -errno if not enabled.  Duplicate same for stub below.  Thanks,  
> 
> Because pcie_enable_tph(PCI_TPH_ST_NS_MODE) could also enable TPH,
> but PCI_TPH_ST_NS_MODE mean "The function must use a value of all
> zeros for all Steering Tags" So I think pcie_enable_tph() should
> treat PCI_TPH_ST_NS_MODE as a invalid input.

This doesn't make any sense to me, PCI_TPH_ST_NS_MODE is a valid enable
mode for the TPH capability.  Thanks,

Alex