Re: [PATCH v4 07/24] PCI/sysfs: Convert PCI resource files to static attributes

Ilpo Järvinen
2026-04-13T11:33:42Z

[-- Attachment #1: Type: text/plain, Size: 12347 bytes --]

On Sat, 11 Apr 2026, Krzysztof Wilczyński wrote:

> Currently, the PCI resource files (resourceN, resourceN_wc) are
> dynamically created by pci_create_sysfs_dev_files(), called from
> both pci_bus_add_device() and the pci_sysfs_init() late_initcall,
> with only a sysfs_initialized flag for synchronisation. This has
> caused "duplicate filename" warnings and boot panics when both
> paths race on the same device.
>
> This is especially likely on Devicetree-based platforms, where the
> PCI host controllers are platform drivers that probe via the driver
> model, which can happen during or after the late_initcall. As such,
> pci_bus_add_device() and pci_sysfs_init() are more likely to overlap.
>
> Thus, convert to static const attributes with three attribute groups
> (I/O, UC, WC), each with an .is_bin_visible callback that checks
> resource flags, BAR length, and non_mappable_bars. A .bin_size
> callback provides pci_resource_len() to the kernfs node for correct
> stat and lseek behaviour.
>
> As part of this conversion:
>
> - Rename pci_read_resource_io() and pci_write_resource_io() to
> pci_read_resource() and pci_write_resource() since the callbacks
> are no longer I/O-specific in the static attribute context.
>
> - Remove pci_create_resource_files(), pci_remove_resource_files(),
> and pci_create_attr() which are no longer needed.
>
> - Move the __weak stubs outside the #if guard so they remain
> available for callers converted in subsequent commits.
>
> Platforms that do not define the HAVE_PCI_MMAP macro or the
> ARCH_GENERIC_PCI_MMAP_RESOURCE macro, such as Alpha architecture,
> continue using their platform-specific resource file creation.
>
> For reference, the dynamic creation dates back to the pre-Git era:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/drivers/pci/pci-sysfs.c?id=42298be0eeb5ae98453b3374c36161b05a46c5dc
>
> The write-combine support was added in commit 45aec1ae72fc ("x86: PAT
> export resource_wc in pci sysfs").
>
> Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
> ---
> drivers/pci/pci-sysfs.c | 242 +++++++++++++++++++++-------------------
> include/linux/pci.h | 2 -
> 2 files changed, 127 insertions(+), 117 deletions(-)
>
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index ca0074674acc..2922905ff070 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -1200,14 +1200,14 @@ static ssize_t pci_resource_io(struct file *filp, struct kobject *kobj,
> #endif
> }
>
> -static ssize_t pci_read_resource_io(struct file *filp, struct kobject *kobj,
> +static ssize_t pci_read_resource(struct file *filp, struct kobject *kobj,
> const struct bin_attribute *attr, char *buf,
> loff_t off, size_t count)
> {
> return pci_resource_io(filp, kobj, attr, buf, off, count, false);
> }
>
> -static ssize_t pci_write_resource_io(struct file *filp, struct kobject *kobj,
> +static ssize_t pci_write_resource(struct file *filp, struct kobject *kobj,
> const struct bin_attribute *attr, char *buf,
> loff_t off, size_t count)
> {
> @@ -1261,129 +1261,136 @@ static const struct bin_attribute dev_resource##_bar##_wc_attr = { \
> .mmap = pci_mmap_resource_wc, \
> }
>
> -/**
> - * pci_remove_resource_files - cleanup resource files
> - * @pdev: dev to cleanup
> - *
> - * If we created resource files for @pdev, remove them from sysfs and
> - * free their resources.
> - */
> -static void pci_remove_resource_files(struct pci_dev *pdev)
> +static inline umode_t
> +__pci_resource_attr_is_visible(struct kobject *kobj,
> + const struct bin_attribute *a,
> + int bar, bool write_combine,
> + unsigned long flags)
> {
> - int i;
> + struct pci_dev *pdev = to_pci_dev(kobj_to_dev(kobj));
>
> - for (i = 0; i < PCI_STD_NUM_BARS; i++) {
> - struct bin_attribute *res_attr;
> -
> - res_attr = pdev->res_attr[i];
> - if (res_attr) {
> - sysfs_remove_bin_file(&pdev->dev.kobj, res_attr);
> - kfree(res_attr);
> - }
> -
> - res_attr = pdev->res_attr_wc[i];
> - if (res_attr) {
> - sysfs_remove_bin_file(&pdev->dev.kobj, res_attr);
> - kfree(res_attr);
> - }
> - }
> -}
> -
> -static int pci_create_attr(struct pci_dev *pdev, int num, int write_combine)
> -{
> - /* allocate attribute structure, piggyback attribute name */
> - int name_len = write_combine ? 13 : 10;
> - struct bin_attribute *res_attr;
> - char *res_attr_name;
> - int retval;
> -
> - res_attr = kzalloc(sizeof(*res_attr) + name_len, GFP_ATOMIC);
> - if (!res_attr)
> - return -ENOMEM;
> -
> - res_attr_name = (char *)(res_attr + 1);
> -
> - sysfs_bin_attr_init(res_attr);
> - if (write_combine) {
> - sprintf(res_attr_name, "resource%d_wc", num);
> - res_attr->mmap = pci_mmap_resource_wc;
> - } else {
> - sprintf(res_attr_name, "resource%d", num);
> - if (pci_resource_flags(pdev, num) & IORESOURCE_IO) {
> - res_attr->read = pci_read_resource_io;
> - res_attr->write = pci_write_resource_io;
> - if (arch_can_pci_mmap_io())
> - res_attr->mmap = pci_mmap_resource_uc;
> - } else {
> - res_attr->mmap = pci_mmap_resource_uc;
> - }
> - }
> - if (res_attr->mmap) {
> - res_attr->f_mapping = iomem_get_mapping;
> - /*
> - * generic_file_llseek() consults f_mapping->host to determine
> - * the file size. As iomem_inode knows nothing about the
> - * attribute, it's not going to work, so override it as well.
> - */
> - res_attr->llseek = pci_llseek_resource;
> - }
> - res_attr->attr.name = res_attr_name;
> - res_attr->attr.mode = 0600;
> - res_attr->size = pci_resource_len(pdev, num);
> - res_attr->private = (void *)(unsigned long)num;
> - retval = sysfs_create_bin_file(&pdev->dev.kobj, res_attr);
> - if (retval) {
> - kfree(res_attr);
> - return retval;
> - }
> -
> - if (write_combine)
> - pdev->res_attr_wc[num] = res_attr;
> - else
> - pdev->res_attr[num] = res_attr;
> -
> - return 0;
> -}
> -
> -/**
> - * pci_create_resource_files - create resource files in sysfs for @dev
> - * @pdev: dev in question
> - *
> - * Walk the resources in @pdev creating files for each resource available.
> - */
> -static int pci_create_resource_files(struct pci_dev *pdev)
> -{
> - int i;
> - int retval;
> -
> - /* Skip devices with non-mappable BARs */
> if (pdev->non_mappable_bars)
> return 0;
>
> - /* Expose the PCI resources from this device as files */
> - for (i = 0; i < PCI_STD_NUM_BARS; i++) {
> + if (!pci_resource_len(pdev, bar))
> + return 0;

Hi,

Did you accidently forget to address some of the comments as I thought you
were agreeing to changing this to resource_assigned() but I found no
resource_assigned() from entire series?

--
i.

>
> - /* skip empty resources */
> - if (!pci_resource_len(pdev, i))
> - continue;
> + if ((pci_resource_flags(pdev, bar) & flags) != flags)
> + return 0;
>
> - retval = pci_create_attr(pdev, i, 0);
> - /* for prefetchable resources, create a WC mappable file */
> - if (!retval && arch_can_pci_mmap_wc() &&
> - pci_resource_flags(pdev, i) & IORESOURCE_PREFETCH)
> - retval = pci_create_attr(pdev, i, 1);
> - if (retval) {
> - pci_remove_resource_files(pdev);
> - return retval;
> - }
> - }
> - return 0;
> + if (write_combine && !arch_can_pci_mmap_wc())
> + return 0;
> +
> + return a->attr.mode;
> }
> -#else /* !(defined(HAVE_PCI_MMAP) || defined(ARCH_GENERIC_PCI_MMAP_RESOURCE)) */
> -int __weak pci_create_resource_files(struct pci_dev *dev) { return 0; }
> -void __weak pci_remove_resource_files(struct pci_dev *dev) { return; }
> +
> +static umode_t pci_dev_resource_io_is_visible(struct kobject *kobj,
> + const struct bin_attribute *a,
> + int n)
> +{
> + return __pci_resource_attr_is_visible(kobj, a, n, false,
> + IORESOURCE_IO);
> +}
> +
> +static umode_t pci_dev_resource_uc_is_visible(struct kobject *kobj,
> + const struct bin_attribute *a,
> + int n)
> +{
> + return __pci_resource_attr_is_visible(kobj, a, n, false,
> + IORESOURCE_MEM);
> +}
> +
> +static umode_t pci_dev_resource_wc_is_visible(struct kobject *kobj,
> + const struct bin_attribute *a,
> + int n)
> +{
> + return __pci_resource_attr_is_visible(kobj, a, n, true,
> + IORESOURCE_MEM | IORESOURCE_PREFETCH);
> +}
> +
> +static size_t pci_dev_resource_bin_size(struct kobject *kobj,
> + const struct bin_attribute *a,
> + int n)
> +{
> + struct pci_dev *pdev = to_pci_dev(kobj_to_dev(kobj));
> +
> + return pci_resource_len(pdev, n);
> +}
> +
> +pci_dev_resource_io_attr(0);
> +pci_dev_resource_io_attr(1);
> +pci_dev_resource_io_attr(2);
> +pci_dev_resource_io_attr(3);
> +pci_dev_resource_io_attr(4);
> +pci_dev_resource_io_attr(5);
> +
> +pci_dev_resource_uc_attr(0);
> +pci_dev_resource_uc_attr(1);
> +pci_dev_resource_uc_attr(2);
> +pci_dev_resource_uc_attr(3);
> +pci_dev_resource_uc_attr(4);
> +pci_dev_resource_uc_attr(5);
> +
> +pci_dev_resource_wc_attr(0);
> +pci_dev_resource_wc_attr(1);
> +pci_dev_resource_wc_attr(2);
> +pci_dev_resource_wc_attr(3);
> +pci_dev_resource_wc_attr(4);
> +pci_dev_resource_wc_attr(5);
> +
> +static const struct bin_attribute *const pci_dev_resource_io_attrs[] = {
> + &dev_resource0_io_attr,
> + &dev_resource1_io_attr,
> + &dev_resource2_io_attr,
> + &dev_resource3_io_attr,
> + &dev_resource4_io_attr,
> + &dev_resource5_io_attr,
> + NULL,
> +};
> +
> +static const struct bin_attribute *const pci_dev_resource_uc_attrs[] = {
> + &dev_resource0_uc_attr,
> + &dev_resource1_uc_attr,
> + &dev_resource2_uc_attr,
> + &dev_resource3_uc_attr,
> + &dev_resource4_uc_attr,
> + &dev_resource5_uc_attr,
> + NULL,
> +};
> +
> +static const struct bin_attribute *const pci_dev_resource_wc_attrs[] = {
> + &dev_resource0_wc_attr,
> + &dev_resource1_wc_attr,
> + &dev_resource2_wc_attr,
> + &dev_resource3_wc_attr,
> + &dev_resource4_wc_attr,
> + &dev_resource5_wc_attr,
> + NULL,
> +};
> +
> +static const struct attribute_group pci_dev_resource_io_attr_group = {
> + .bin_attrs = pci_dev_resource_io_attrs,
> + .is_bin_visible = pci_dev_resource_io_is_visible,
> + .bin_size = pci_dev_resource_bin_size,
> +};
> +
> +static const struct attribute_group pci_dev_resource_uc_attr_group = {
> + .bin_attrs = pci_dev_resource_uc_attrs,
> + .is_bin_visible = pci_dev_resource_uc_is_visible,
> + .bin_size = pci_dev_resource_bin_size,
> +};
> +
> +static const struct attribute_group pci_dev_resource_wc_attr_group = {
> + .bin_attrs = pci_dev_resource_wc_attrs,
> + .is_bin_visible = pci_dev_resource_wc_is_visible,
> + .bin_size = pci_dev_resource_bin_size,
> +};
> +
> #endif
>
> +int __weak pci_create_resource_files(struct pci_dev *dev) { return 0; }
> +void __weak pci_remove_resource_files(struct pci_dev *dev) { }
> +
> /**
> * pci_write_rom - used to enable access to the PCI ROM display
> * @filp: sysfs file
> @@ -1861,6 +1868,11 @@ static const struct attribute_group pci_dev_group = {
>
> const struct attribute_group *pci_dev_groups[] = {
> &pci_dev_group,
> +#if defined(HAVE_PCI_MMAP) || defined(ARCH_GENERIC_PCI_MMAP_RESOURCE)
> + &pci_dev_resource_io_attr_group,
> + &pci_dev_resource_uc_attr_group,
> + &pci_dev_resource_wc_attr_group,
> +#endif
> &pci_dev_config_attr_group,
> &pci_dev_rom_attr_group,
> &pci_dev_reset_attr_group,
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 05aceb7f1f37..9c0782899ef9 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -2526,10 +2526,8 @@ int pcibios_alloc_irq(struct pci_dev *dev);
> void pcibios_free_irq(struct pci_dev *dev);
> resource_size_t pcibios_default_alignment(void);
>
> -#if !defined(HAVE_PCI_MMAP) && !defined(ARCH_GENERIC_PCI_MMAP_RESOURCE)
> extern int pci_create_resource_files(struct pci_dev *dev);
> extern void pci_remove_resource_files(struct pci_dev *dev);
> -#endif
>
> #if defined(CONFIG_PCI_MMCONFIG) || defined(CONFIG_ACPI_MCFG)
> void __init pci_mmcfg_early_init(void);
>