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

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