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

Ilpo Järvinen
2026-04-13T11:51:58Z

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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 <ilpo.jarvinen@linux.intel.com>

> 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 <kwilczynski@kernel.org>
> ---
> 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);
> }
>
>

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i.