Re: [PATCH v4 12/24] alpha/PCI: Use BAR index in sysfs attr->private instead of resource pointer

On Sat, 11 Apr 2026, Krzysztof Wilczyński wrote:

> Currently, Alpha's pci_create_one_attr() stores a resource pointer in
> attr->private, and pci_mmap_resource() loops through all BARs to find
> the matching index.
> 
> Thus, store the BAR index directly in attr->private and retrieve the
> resource via pci_resource_n().  This eliminates the loop and aligns
> with the convention used by the generic PCI sysfs code.
> 
> While at it, add parentheses around the bitwise flag test in
> pci_mmap_resource() to make the precedence explicit, and to
> match the preferred style.

Probably not necessary to touch this line now at all as you're going to 
replace it two patches later anyway so it just adds noise.

Reviewed-by: Ilpo Järvinen <[email protected]>

> The PCI core change was first added in the commit dca40b186b75 ("PCI:
> Use BAR index in sysfs attr->private instead of resource pointer").
> 
> Signed-off-by: Krzysztof Wilczyński <[email protected]>
> ---
>  arch/alpha/kernel/pci-sysfs.c | 17 ++++++-----------
>  1 file changed, 6 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/alpha/kernel/pci-sysfs.c b/arch/alpha/kernel/pci-sysfs.c
> index 2324720c3e83..c84867ce31f5 100644
> --- a/arch/alpha/kernel/pci-sysfs.c
> +++ b/arch/alpha/kernel/pci-sysfs.c
> @@ -69,25 +69,20 @@ static int pci_mmap_resource(struct kobject *kobj,
>  			     struct vm_area_struct *vma, int sparse)
>  {
>  	struct pci_dev *pdev = to_pci_dev(kobj_to_dev(kobj));
> -	struct resource *res = attr->private;
> +	int barno = (unsigned long)attr->private;
> +	struct resource *res = pci_resource_n(pdev, barno);
>  	enum pci_mmap_state mmap_type;
>  	struct pci_bus_region bar;
> -	int i, ret;
> +	int ret;
>  
>  	ret = security_locked_down(LOCKDOWN_PCI_ACCESS);
>  	if (ret)
>  		return ret;
>  
> -	for (i = 0; i < PCI_STD_NUM_BARS; i++)
> -		if (res == &pdev->resource[i])
> -			break;
> -	if (i >= PCI_STD_NUM_BARS)
> -		return -ENODEV;
> -
> -	if (res->flags & IORESOURCE_MEM && iomem_is_exclusive(res->start))
> +	if ((res->flags & IORESOURCE_MEM) && iomem_is_exclusive(res->start))
>  		return -EINVAL;
>  
> -	if (!__pci_mmap_fits(pdev, i, vma, sparse))
> +	if (!__pci_mmap_fits(pdev, barno, vma, sparse))
>  		return -EINVAL;
>  
>  	pcibios_resource_to_bus(pdev->bus, &bar, res);
> @@ -170,7 +165,7 @@ static int pci_create_one_attr(struct pci_dev *pdev, int num, char *name,
>  	res_attr->attr.name = name;
>  	res_attr->attr.mode = S_IRUSR | S_IWUSR;
>  	res_attr->size = sparse ? size << 5 : size;
> -	res_attr->private = &pdev->resource[num];
> +	res_attr->private = (void *)(unsigned long)num;
>  	return sysfs_create_bin_file(&pdev->dev.kobj, res_attr);
>  }
>  
> 

-- 
 i.