Re: [PATCH v19 07/18] PCI/TPH: Add pcie_tph_supported() helper to check TPH capability attributes

[Alex Williamson <alex@shazbot.org>]

On Thu, 2 Jul 2026 20:42:13 +0800
Chengwen Feng <fengchengwen@huawei.com> wrote:

> Add new helper pcie_tph_supported() with want_ext parameter:
> - want_ext = false: Check if device has valid TPH capability;
> - want_ext = true: Check hardware Extended TPH support.

Ugh, more bool args.  Like 6, I'm not sure why we need to abstract
these structure fields.  Is this trying to create an ABI for external
modules or is it trying to simplify code paths based on whether TPH is
configured.  These could just be macros:

#define pcie_ext_tph_supported(pdev) \
	((pdev)->tph_max_type == PCI_TPH_REQ_EXT_TPH)

#define pcie_std_tph_supported(pdev) \
	((pdev)->tph_max_type >= PCI_TPH_REQ_TPH_ONLY)

With the corresponding (false) in the !CONFIG case, or the caller just
tests the field itself if it's already conditionally compiled.  Thanks,

Alex

 
> This helper is prepared for follow-up VFIO TPH virtualization patches to
> uniformly query basic TPH existence and Extended TPH capability.
> 
> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
> ---
>  drivers/pci/tph.c       | 19 +++++++++++++++++++
>  include/linux/pci-tph.h |  3 +++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/pci/tph.c b/drivers/pci/tph.c
> index ea777cc33ae6..c080cf5401a3 100644
> --- a/drivers/pci/tph.c
> +++ b/drivers/pci/tph.c
> @@ -596,3 +596,22 @@ void pci_tph_init(struct pci_dev *pdev)
>  	save_size = sizeof(u32) + num_entries * sizeof(u16);
>  	pci_add_ext_cap_save_buffer(pdev, PCI_EXT_CAP_ID_TPH, save_size);
>  }
> +
> +/**
> + * pcie_tph_supported - Check TPH capability attribute
> + * @pdev: PCI device to query
> + * @want_ext: false - check TPH cap exists; true - check EXT_TPH support
> + *
> + * Return: true on matched condition, false otherwise
> + */
> +bool pcie_tph_supported(struct pci_dev *pdev, bool want_ext)
> +{
> +	if (!pdev->tph_cap)
> +		return false;
> +
> +	if (!want_ext)
> +		return true;
> +
> +	return pdev->tph_ext_support;
> +}
> +EXPORT_SYMBOL(pcie_tph_supported);
> diff --git a/include/linux/pci-tph.h b/include/linux/pci-tph.h
> index e4f7045fc152..5917a0694c1d 100644
> --- a/include/linux/pci-tph.h
> +++ b/include/linux/pci-tph.h
> @@ -36,6 +36,7 @@ int pcie_enable_tph_explicit(struct pci_dev *pdev, int mode, bool extended);
>  u8 pcie_tph_enabled_req_type(struct pci_dev *pdev);
>  u16 pcie_tph_get_st_table_size(struct pci_dev *pdev);
>  u32 pcie_tph_get_st_table_loc(struct pci_dev *pdev);
> +bool pcie_tph_supported(struct pci_dev *pdev, bool want_ext);
>  #else
>  static inline int pcie_tph_set_st_entry(struct pci_dev *pdev,
>  					unsigned int index, u16 tag)
> @@ -60,6 +61,8 @@ static inline u16 pcie_tph_get_st_table_size(struct pci_dev *pdev)
>  { return 0; }
>  static inline u32 pcie_tph_get_st_table_loc(struct pci_dev *pdev)
>  { return PCI_TPH_LOC_NONE; }
> +static inline bool pcie_tph_supported(struct pci_dev *pdev, bool want_ext)
> +{ return false; }
>  #endif
>  
>  #endif /* LINUX_PCI_TPH_H */