diff options
| author | David Woodhouse <dwmw@amazon.co.uk> | 2017-04-12 14:25:54 +0200 |
|---|---|---|
| committer | Bjorn Helgaas <bhelgaas@google.com> | 2017-04-18 20:01:42 +0200 |
| commit | ae749c7ab475de2c9c427058db19921c91846e89 (patch) | |
| tree | 0fbb5e8de9c0827c196f5296409622beb5e9aec9 /Documentation/filesystems | |
| parent | xtensa/PCI: Do not mmap PCI BARs to userspace as write-through (diff) | |
| download | linux-ae749c7ab475de2c9c427058db19921c91846e89.tar.xz linux-ae749c7ab475de2c9c427058db19921c91846e89.zip | |
PCI: Add arch_can_pci_mmap_wc() macro
Most of the almost-identical versions of pci_mmap_page_range() silently
ignore the 'write_combine' argument and give uncached mappings.
Yet we allow the PCIIOC_WRITE_COMBINE ioctl in /proc/bus/pci, expose the
'resourceX_wc' file in sysfs, and allow an attempted mapping to apparently
succeed.
To fix this, introduce a macro arch_can_pci_mmap_wc() which indicates
whether the platform can do a write-combining mapping. On x86 this ends up
being pat_enabled(), while the few other platforms that support it can just
set it to a literal '1'.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/sysfs-pci.txt | 4 |
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. |