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* [PATCH] PCI: Change return type of pci_find_capability()
@ 2020-11-17 19:17 Puranjay Mohan
  2020-11-24 19:53 ` Bjorn Helgaas
  0 siblings, 1 reply; 2+ messages in thread
From: Puranjay Mohan @ 2020-11-17 19:17 UTC (permalink / raw)
  To: bjorn; +Cc: Puranjay Mohan, linux-pci, linux-kernel-mentees, skhan

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.

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);
 	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


^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH] PCI: Change return type of pci_find_capability()
  2020-11-17 19:17 [PATCH] PCI: Change return type of pci_find_capability() Puranjay Mohan
@ 2020-11-24 19:53 ` Bjorn Helgaas
  0 siblings, 0 replies; 2+ messages in thread
From: Bjorn Helgaas @ 2020-11-24 19:53 UTC (permalink / raw)
  To: Puranjay Mohan; +Cc: bjorn, linux-pci, linux-kernel-mentees, skhan

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
> 

^ permalink raw reply	[flat|nested] 2+ messages in thread

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