Re: [PATCH] PCI: Change return type of pci_find_capability()

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, Nov 18, 2020 at 12:47:18AM +0530, Puranjay Mohan wrote:
> PCI Capabilities are linked in a list that must appear in the first 256 bytes of config space.
> The Capabilities Pointer register at 0x34 contains the address of the first Capability in the list.
> Each Capability contains an 8 bit "Next Capability Pointer" that is set to 0x00 in the last item of the list.
> 
> Change the return type of pci_find_capability() from int to u8 to match the specification.

Nits: Be more specific in subject, e.g., "Return u8 from
pci_find_capability()".   Wrap commit log to fit in 78 columns.  Add
blank lines between paragraphs.  The 0x34 address is accurate but not
relevant to this patch.

> Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
> ---
>  drivers/pci/pci.c   | 4 ++--
>  include/linux/pci.h | 4 ++--
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 6d4d5a2f923d..05ac8a493e6b 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -477,9 +477,9 @@ static int __pci_bus_find_cap_start(struct pci_bus *bus,
>   *  %PCI_CAP_ID_PCIX         PCI-X
>   *  %PCI_CAP_ID_EXP          PCI Express
>   */
> -int pci_find_capability(struct pci_dev *dev, int cap)
> +u8 pci_find_capability(struct pci_dev *dev, int cap)
>  {
> -	int pos;
> +	u8 pos;
>  
>  	pos = __pci_bus_find_cap_start(dev->bus, dev->devfn, dev->hdr_type);

Also change the signatures of __pci_bus_find_cap_start(),
__pci_find_next_cap(), __pci_find_next_cap_ttl() to match.

>  	if (pos)
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 22207a79762c..19a817702ea9 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1063,7 +1063,7 @@ void pci_sort_breadthfirst(void);
>  
>  /* Generic PCI functions exported to card drivers */
>  
> -int pci_find_capability(struct pci_dev *dev, int cap);
> +u8 pci_find_capability(struct pci_dev *dev, int cap);
>  int pci_find_next_capability(struct pci_dev *dev, u8 pos, int cap);
>  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);
> @@ -1719,7 +1719,7 @@ static inline int __pci_register_driver(struct pci_driver *drv,
>  static inline int pci_register_driver(struct pci_driver *drv)
>  { return 0; }
>  static inline void pci_unregister_driver(struct pci_driver *drv) { }
> -static inline int pci_find_capability(struct pci_dev *dev, int cap)
> +static inline u8 pci_find_capability(struct pci_dev *dev, int cap)
>  { return 0; }
>  static inline int pci_find_next_capability(struct pci_dev *dev, u8 post,
>  					   int cap)
> -- 
> 2.27.0
>