diff options
| author | venkatesh.pallipadi@intel.com <venkatesh.pallipadi@intel.com> | 2008-12-19 13:47:30 -0800 |
|---|---|---|
| committer | H. Peter Anvin <hpa@zytor.com> | 2008-12-19 15:40:31 -0800 |
| commit | 67bac792cd0c05b4b6e0393c32605b028b8dd533 (patch) | |
| tree | 03e978a671180abbd634e40add6a29b1887334ca /Documentation | |
| parent | 34801ba9bf0381fcf0e2b08179d2c07f2c6ede74 (diff) | |
x86: PAT: pfnmap documentation update changes
Impact: Documentation only.
Documentation updates as per Randy Dunlap's comments.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/x86/pat.txt | 10 |
1 files changed, 5 insertions, 5 deletions
diff --git a/Documentation/x86/pat.txt b/Documentation/x86/pat.txt index 1784ff27699..cf08c9fff3c 100644 --- a/Documentation/x86/pat.txt +++ b/Documentation/x86/pat.txt @@ -82,23 +82,23 @@ pci proc | -- | -- | WC | Advanced APIs for drivers ------------------------- -A. Exporting pages to user with remap_pfn_range, io_remap_pfn_range, +A. Exporting pages to users with remap_pfn_range, io_remap_pfn_range, vm_insert_pfn -Drivers wanting to export some pages to userspace, do it by using mmap +Drivers wanting to export some pages to userspace do it by using mmap interface and a combination of 1) pgprot_noncached() 2) io_remap_pfn_range() or remap_pfn_range() or vm_insert_pfn() -With pat support, a new API pgprot_writecombine is being added. So, driver can +With PAT support, a new API pgprot_writecombine is being added. So, drivers can continue to use the above sequence, with either pgprot_noncached() or pgprot_writecombine() in step 1, followed by step 2. In addition, step 2 internally tracks the region as UC or WC in memtype list in order to ensure no conflicting mapping. -Note that this set of APIs only work with IO (non RAM) regions. If driver -wants to export RAM region, it has to do set_memory_uc() or set_memory_wc() +Note that this set of APIs only works with IO (non RAM) regions. If driver +wants to export a RAM region, it has to do set_memory_uc() or set_memory_wc() as step 0 above and also track the usage of those pages and use set_memory_wb() before the page is freed to free pool. |