Re: [PATCH] PCI: add helper function to find DVSEC

[Randy Dunlap <rdunlap@infradead.org>]

On 10/30/20 3:42 PM, Dave Jiang wrote:
> Add function that searches for DVSEC and returns the offset in PCI
> configuration space for the interested DVSEC capability.
> 
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> Reviewed-by: Ashok Raj <ashok.raj@intel.com>
> ---
> 
> The patch has dependency on David Box’s dvsec definition patch:
> https://lore.kernel.org/linux-pci/bc5f059c5bae957daebde699945c80808286bf45.camel@linux.intel.com/T/#m1d0dc12e3b2c739e2c37106a45f325bb8f001774
> 
>  drivers/pci/pci.c   |   30 ++++++++++++++++++++++++++++++
>  include/linux/pci.h |    3 +++
>  2 files changed, 33 insertions(+)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 6d4d5a2f923d..49e57b831509 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -589,6 +589,36 @@ int pci_find_ext_capability(struct pci_dev *dev, int cap)
>  }
>  EXPORT_SYMBOL_GPL(pci_find_ext_capability);
>  
> +/**
> + * pci_find_dvsec - return position of DVSEC with provided vendor and DVSEC ID
> + * @dev: the PCI device
> + * @vendor: vendor for the DVSEC
> + * @id: the DVSEC capibility ID

                     capability

> + *
> + * Return the offset of DVSEC on success or -ENOTSUPP if not found

    * Return: the offset of DVSEC on success or -ENOTSUPP if not found

> + */
> +int pci_find_dvsec(struct pci_dev *dev, u16 vendor, u16 id)
> +{
> +	u16 dev_vendor, dev_id;
> +	int pos;
> +
> +	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DVSEC);
> +	if (!pos)
> +		return -ENOTSUPP;
> +
> +	while (pos) {
> +		pci_read_config_word(dev, pos + PCI_DVSEC_HEADER1, &dev_vendor);
> +		pci_read_config_word(dev, pos + PCI_DVSEC_HEADER2, &dev_id);
> +		if (dev_vendor == vendor && dev_id == id)
> +			return pos;
> +
> +		pos = pci_find_next_ext_capability(dev, pos, PCI_EXT_CAP_ID_DVSEC);
> +	}
> +
> +	return -ENOTSUPP;
> +}
> +EXPORT_SYMBOL_GPL(pci_find_dvsec);
> +
>  /**
>   * pci_get_dsn - Read and return the 8-byte Device Serial Number
>   * @dev: PCI device to query
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 22207a79762c..6c692d32c82a 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1069,6 +1069,7 @@ int pci_find_ext_capability(struct pci_dev *dev, int cap);
>  int pci_find_next_ext_capability(struct pci_dev *dev, int pos, int cap);
>  int pci_find_ht_capability(struct pci_dev *dev, int ht_cap);
>  int pci_find_next_ht_capability(struct pci_dev *dev, int pos, int ht_cap);
> +int pci_find_dvsec(struct pci_dev *dev, u16 vendor, u16 id);
>  struct pci_bus *pci_find_next_bus(const struct pci_bus *from);
>  
>  u64 pci_get_dsn(struct pci_dev *dev);
> @@ -1726,6 +1727,8 @@ static inline int pci_find_next_capability(struct pci_dev *dev, u8 post,
>  { return 0; }
>  static inline int pci_find_ext_capability(struct pci_dev *dev, int cap)
>  { return 0; }
> +static inline int pci_find_dvsec(struct pci_dev *dev, u16 vendor, u16 id)
> +{ return 0; }

Why shouldn't this return -ENOTSUPP instead of 0?

>  
>  static inline u64 pci_get_dsn(struct pci_dev *dev)
>  { return 0; }
> 
> 

-- 
~Randy