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-rw-r--r--Documentation/filesystems/sysfs-pci.txt4
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/filesystems/sysfs-pci.txt b/Documentation/filesystems/sysfs-pci.txt
index 6ea1ceda6f52..25b7f1c1b868 100644
--- a/Documentation/filesystems/sysfs-pci.txt
+++ b/Documentation/filesystems/sysfs-pci.txt
@@ -117,6 +117,10 @@ code must define HAVE_PCI_MMAP and provide a pci_mmap_page_range function.
Platforms are free to only support subsets of the mmap functionality, but
useful return codes should be provided.
+Platforms which support write-combining maps of PCI resources must define
+arch_can_pci_mmap_wc() which shall evaluate to non-zero at runtime when
+write-combining is permitted.
+
Legacy resources are protected by the HAVE_PCI_LEGACY define. Platforms
wishing to support legacy functionality should define it and provide
pci_legacy_read, pci_legacy_write and pci_mmap_legacy_page_range functions.