[PATCH v2 1/7] PCI/sysfs: Add pci_dev_resource_attr_is_visible() helper

["Krzysztof Wilczyński" <kw@linux.com>]

This helper controls how a static sysfs attribute is exposed, where
depending on whether a particular resource is available (the BAR address
space requested has non-zero size) or whether the write-combine feature
is supported, the sysfs attribute will be made either visible or hidden.

After the conversion to use static sysfs objects when exposing each PCI
BAR address space this helper is to be called from the .is_bin_visible()
callback for each of the PCI resources attributes groups.

A single BAR will have a dedicated attribute group with two attributes
in it - one normal resource and one that can potentially support the
write-combine feature.

Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
---
 drivers/pci/pci-sysfs.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 7fb5cd17cc98..4272d1aba205 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -1237,6 +1237,30 @@ static int pci_create_resource_files(struct pci_dev *pdev)
 	}
 	return 0;
 }
+
+static umode_t pci_dev_resource_attr_is_visible(struct kobject *kobj,
+						struct bin_attribute *a,
+						int bar, bool write_combine)
+{
+	struct pci_dev *pdev = to_pci_dev(kobj_to_dev(kobj));
+	resource_size_t resource_size = pci_resource_len(pdev, bar);
+	bool prefetch;
+
+	if (!resource_size)
+		return 0;
+
+	prefetch = (pci_resource_flags(pdev, bar) &
+		    (IORESOURCE_MEM | IORESOURCE_PREFETCH)) ==
+			(IORESOURCE_MEM | IORESOURCE_PREFETCH);
+
+	if (write_combine && !(prefetch && arch_can_pci_mmap_wc()))
+		return 0;
+
+	a->size = resource_size;
+
+	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; }
-- 
2.33.0