Subject: [PATCH 18/20] PCI/sysfs: Add __weak pci_legacy_has_sparse() helper

From: Krzysztof Wilczyński <[email-masked]>
Date: Fri, 10 Apr 2026 05:50:38 +0000

Currently, Alpha's sparse/dense legacy attribute handling is done via
pci_adjust_legacy_attr(), which updates dynamically allocated attributes
at runtime.  The upcoming conversion to static attributes needs a way
to determine sparse support at visibility check time.

Add a __weak pci_legacy_has_sparse() that returns false by default.
Alpha overrides it to check has_sparse() on the bus host controller.

Signed-off-by: Krzysztof Wilczyński <[email-masked]>
---
 arch/alpha/kernel/pci-sysfs.c | 7 +++++++
 drivers/pci/pci-sysfs.c       | 6 ++++++
 drivers/pci/pci.h             | 4 ++++
 3 files changed, 17 insertions(+)

diff --git a/arch/alpha/kernel/pci-sysfs.c b/arch/alpha/kernel/pci-sysfs.c
index 2da95d965e9c..2031a3b6972c 100644
--- a/arch/alpha/kernel/pci-sysfs.c
+++ b/arch/alpha/kernel/pci-sysfs.c
@@ -190,6 +190,13 @@ int pci_mmap_legacy_page_range(struct pci_bus *bus, struct vm_area_struct *vma,
 	return hose_mmap_page_range(hose, vma, mmap_type, sparse);
 }
 
+bool pci_legacy_has_sparse(struct pci_bus *bus, enum pci_mmap_state type)
+{
+	struct pci_controller *hose = bus->sysdata;
+
+	return has_sparse(hose, type);
+}
+
 /**
  * pci_adjust_legacy_attr - adjustment of legacy file attributes
  * @bus: bus to create files under
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 40b5e21d77f3..fe079fb31dce 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -1019,6 +1019,12 @@ static int pci_mmap_legacy_io(struct file *filp, struct kobject *kobj,
 	return pci_mmap_legacy_page_range(bus, vma, pci_mmap_io);
 }
 
+bool __weak pci_legacy_has_sparse(struct pci_bus *bus,
+				  enum pci_mmap_state type)
+{
+	return false;
+}
+
 /**
  * pci_adjust_legacy_attr - adjustment of legacy file attributes
  * @b: bus to create files under
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 1bf165595583..f52caf7e4d13 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -390,6 +390,10 @@ static inline int pci_no_d1d2(struct pci_dev *dev)
 
 }
 
+#ifdef HAVE_PCI_LEGACY
+bool pci_legacy_has_sparse(struct pci_bus *bus, enum pci_mmap_state type);
+#endif
+
 #ifdef CONFIG_SYSFS
 extern const struct attribute_group *pci_dev_groups[];
 extern const struct attribute_group *pci_dev_attr_groups[];
-- 
2.53.0