PCI/sysfs: Convert PCI resource files to static attributes

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 warnings and
boot panics when both paths race on the same device, e.g.:

  sysfs: cannot create duplicate filename '/devices/pci0000:3c/0000:3c:01.0/0000:3e:00.2/resource2'

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.

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").

Many other reports mentioned in the cover letter (first Link: below).

Link: https://lore.kernel.org/r/20260508043543.217179-1-kwilczynski@kernel.org/
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=215515
Closes: https://github.com/openwrt/openwrt/issues/17143
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Shivaprasad G Bhat <sbhat@linux.ibm.com>
Link: https://patch.msgid.link/20260508043543.217179-8-kwilczynski@kernel.org

1 files changed, 0 insertions, 2 deletions

diff --git a/include/linux/pci.h b/include/linux/pci.h
index e93fbe6b57fe..974605c9fce2 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -2531,10 +2531,8 @@ 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);