[PATCH] PCI: endpoint: use ffz() instead of find_first_zero_bit()

[PATCH] PCI: endpoint: use ffz() instead of find_first_zero_bit()

[Niklas Cassel]

find_first_zero_bit()'s parameter 'size' is defined in bits,
not in bytes.

Calling find_first_zero_bit() with the wrong size unit
will lead to insidious bugs.

Fix this by using replacing find_first_zero_bit() with ffz(),
since ffz() only works on a single 'unsigned long' and therefore
does not need a size argument.

Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
---
 drivers/pci/endpoint/pci-ep-cfs.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/pci/endpoint/pci-ep-cfs.c b/drivers/pci/endpoint/pci-ep-cfs.c
index 4f74386c1ced..96b984685640 100644
--- a/drivers/pci/endpoint/pci-ep-cfs.c
+++ b/drivers/pci/endpoint/pci-ep-cfs.c
@@ -108,8 +108,7 @@ static int pci_epc_epf_link(struct config_item *epc_item,
 	if (ret)
 		goto err_add_epf;
 
-	func_no = find_first_zero_bit(&epc_group->function_num_map,
-				      sizeof(epc_group->function_num_map));
+	func_no = ffz(epc_group->function_num_map);
 	set_bit(func_no, &epc_group->function_num_map);
 	epf->func_no = func_no;
 
-- 
2.14.2

RE: [PATCH] PCI: endpoint: use ffz() instead of find_first_zero_bit()

[David Laight]

From: Niklas Cassel
> Sent: 17 November 2017 09:43
> find_first_zero_bit()'s parameter 'size' is defined in bits,
> not in bytes.
> 
> Calling find_first_zero_bit() with the wrong size unit
> will lead to insidious bugs.
> 
> Fix this by using replacing find_first_zero_bit() with ffz(),
> since ffz() only works on a single 'unsigned long' and therefore
> does not need a size argument.
> 
> Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
> ---
>  drivers/pci/endpoint/pci-ep-cfs.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/endpoint/pci-ep-cfs.c b/drivers/pci/endpoint/pci-ep-cfs.c
> index 4f74386c1ced..96b984685640 100644
> --- a/drivers/pci/endpoint/pci-ep-cfs.c
> +++ b/drivers/pci/endpoint/pci-ep-cfs.c
> @@ -108,8 +108,7 @@ static int pci_epc_epf_link(struct config_item *epc_item,
>  	if (ret)
>  		goto err_add_epf;
> 
> -	func_no = find_first_zero_bit(&epc_group->function_num_map,
> -				      sizeof(epc_group->function_num_map));
> +	func_no = ffz(epc_group->function_num_map);
>  	set_bit(func_no, &epc_group->function_num_map);
>  	epf->func_no = func_no;

Is set_bit() now setting the correct bit?
I'd guess that:
	epc_group->function_num_map |= 1ul << func_no;
would be more accurate?

	David