Re: [PATCH 1/2] PCI: Add pci_find_next_dvsec_capability to find next designated VSEC

[Andrew Donnellan <ajd@linux.ibm.com>]

On Mon, 2023-08-07 at 11:18 +0800, Xiongfeng Wang wrote:
> Some devices may have several DVSEC(Designated Vendor-Specific
> Extended
> Capability) entries with the same DVSEC ID. Add
> pci_find_next_dvsec_capability() to find them all.
> 
> Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
> 

Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>

> ---
>  drivers/pci/pci.c   | 37 +++++++++++++++++++++++++------------
>  include/linux/pci.h |  2 ++
>  2 files changed, 27 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 60230da957e0..3455ca7306ae 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -749,35 +749,48 @@ u16 pci_find_vsec_capability(struct pci_dev
> *dev, u16 vendor, int cap)
>  EXPORT_SYMBOL_GPL(pci_find_vsec_capability);
>  
>  /**
> - * pci_find_dvsec_capability - Find DVSEC for vendor
> + * pci_find_next_dvsec_capability - Find next DVSEC for vendor
>   * @dev: PCI device to query
> + * @start: address at which to start looking (0 to start at
> beginning of list)
>   * @vendor: Vendor ID to match for the DVSEC
>   * @dvsec: Designated Vendor-specific capability ID
>   *
> - * If DVSEC has Vendor ID @vendor and DVSEC ID @dvsec return the
> capability
> - * offset in config space; otherwise return 0.
> + * Returns the address of the next DVSEC if the DVSEC has Vendor ID
> @vendor and
> + * DVSEC ID @dvsec; otherwise return 0. DVSEC can occur several
> times with the
> + * same DVSEC ID for some devices, and this provides a way to find
> them all.
>   */
> -u16 pci_find_dvsec_capability(struct pci_dev *dev, u16 vendor, u16
> dvsec)
> +u16 pci_find_next_dvsec_capability(struct pci_dev *dev, u16 start,
> u16 vendor,
> +                                  u16 dvsec)
>  {
> -       int pos;
> +       u16 pos = start;
>  
> -       pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DVSEC);
> -       if (!pos)
> -               return 0;
> -
> -       while (pos) {
> +       while ((pos = pci_find_next_ext_capability(dev, pos,
> +                                                
> PCI_EXT_CAP_ID_DVSEC))) {
>                 u16 v, id;
>  
>                 pci_read_config_word(dev, pos + PCI_DVSEC_HEADER1,
> &v);
>                 pci_read_config_word(dev, pos + PCI_DVSEC_HEADER2,
> &id);
>                 if (vendor == v && dvsec == id)
>                         return pos;
> -
> -               pos = pci_find_next_ext_capability(dev, pos,
> PCI_EXT_CAP_ID_DVSEC);
>         }
>  
>         return 0;
>  }
> +EXPORT_SYMBOL_GPL(pci_find_next_dvsec_capability);
> +
> +/**
> + * pci_find_dvsec_capability - Find DVSEC for vendor
> + * @dev: PCI device to query
> + * @vendor: Vendor ID to match for the DVSEC
> + * @dvsec: Designated Vendor-specific capability ID
> + *
> + * If DVSEC has Vendor ID @vendor and DVSEC ID @dvsec return the
> capability
> + * offset in config space; otherwise return 0.
> + */
> +u16 pci_find_dvsec_capability(struct pci_dev *dev, u16 vendor, u16
> dvsec)
> +{
> +       return pci_find_next_dvsec_capability(dev, 0, vendor, dvsec);
> +}
>  EXPORT_SYMBOL_GPL(pci_find_dvsec_capability);
>  
>  /**
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index c69a2cc1f412..82bb905daf72 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1168,6 +1168,8 @@ u16 pci_find_next_ext_capability(struct pci_dev
> *dev, u16 pos, int cap);
>  struct pci_bus *pci_find_next_bus(const struct pci_bus *from);
>  u16 pci_find_vsec_capability(struct pci_dev *dev, u16 vendor, int
> cap);
>  u16 pci_find_dvsec_capability(struct pci_dev *dev, u16 vendor, u16
> dvsec);
> +u16 pci_find_next_dvsec_capability(struct pci_dev *dev, u16 start,
> u16 vendor,
> +                                  u16 dvsec);
>  
>  u64 pci_get_dsn(struct pci_dev *dev);
>  

-- 
Andrew Donnellan    OzLabs, ADL Canberra
ajd@linux.ibm.com   IBM Australia Limited