[PATCH v6 07/24] PCI/sysfs: Convert PCI resource files to static attributes

Krzysztof Wilczyński
2026-04-22T16:15:15Z

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.

- Update __resource_resize_store() to use sysfs_create_groups() and
sysfs_remove_groups(), which re-evaluates visibility and runs the
.bin_size callback for the static resource attribute groups.

- 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 | 260 +++++++++++++++++++++-------------------
include/linux/pci.h | 2 -
2 files changed, 140 insertions(+), 122 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index e7ca83aec3e8..3508e29f6ad1 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)
{
@@ -1238,8 +1238,8 @@ static ssize_t pci_write_resource_io(struct file *filp, struct kobject *kobj,
static const struct bin_attribute dev_resource##_bar##_io_attr = { \
.attr = { .name = "resource" __stringify(_bar), .mode = 0600 }, \
.private = (void *)(unsigned long)(_bar), \
- .read = pci_read_resource_io, \
- .write = pci_write_resource_io, \
+ .read = pci_read_resource, \
+ .write = pci_write_resource, \
__PCI_RESOURCE_IO_MMAP_ATTRS \
}

@@ -1261,129 +1261,144 @@ 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;

- /* 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,
+};
+
+static const struct attribute_group *pci_dev_resource_attr_groups[] = {
+ &pci_dev_resource_io_attr_group,
+ &pci_dev_resource_uc_attr_group,
+ &pci_dev_resource_wc_attr_group,
+ NULL,
+};
+#else
+#define pci_dev_resource_attr_groups NULL
#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
@@ -1685,14 +1700,14 @@ static ssize_t __resource_resize_store(struct device *dev, int n,
pci_write_config_word(pdev, PCI_COMMAND,
cmd & ~PCI_COMMAND_MEMORY);

- pci_remove_resource_files(pdev);
+ sysfs_remove_groups(&pdev->dev.kobj, pci_dev_resource_attr_groups);

ret = pci_resize_resource(pdev, n, size, 0);

pci_assign_unassigned_bus_resources(bus);

- if (pci_create_resource_files(pdev))
- pci_warn(pdev, "Failed to recreate resource files after BAR resizing\n");
+ if (sysfs_create_groups(&pdev->dev.kobj, pci_dev_resource_attr_groups))
+ pci_warn(pdev, "Failed to recreate resource groups after BAR resizing\n");

pci_write_config_word(pdev, PCI_COMMAND, cmd);
pm_put:
@@ -1861,6 +1876,11 @@ 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);
--
2.54.0