diff options
author | venkatesh.pallipadi@intel.com <venkatesh.pallipadi@intel.com> | 2008-12-19 16:47:30 -0500 |
---|---|---|
committer | H. Peter Anvin <hpa@zytor.com> | 2008-12-19 18:40:31 -0500 |
commit | 67bac792cd0c05b4b6e0393c32605b028b8dd533 (patch) | |
tree | 03e978a671180abbd634e40add6a29b1887334ca /Documentation/x86/pat.txt | |
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/x86/pat.txt')
-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 1784ff276997..cf08c9fff3cd 100644 --- a/Documentation/x86/pat.txt +++ b/Documentation/x86/pat.txt | |||
@@ -82,23 +82,23 @@ pci proc | -- | -- | WC | | |||
82 | 82 | ||
83 | Advanced APIs for drivers | 83 | Advanced APIs for drivers |
84 | ------------------------- | 84 | ------------------------- |
85 | A. Exporting pages to user with remap_pfn_range, io_remap_pfn_range, | 85 | A. Exporting pages to users with remap_pfn_range, io_remap_pfn_range, |
86 | vm_insert_pfn | 86 | vm_insert_pfn |
87 | 87 | ||
88 | Drivers wanting to export some pages to userspace, do it by using mmap | 88 | Drivers wanting to export some pages to userspace do it by using mmap |
89 | interface and a combination of | 89 | interface and a combination of |
90 | 1) pgprot_noncached() | 90 | 1) pgprot_noncached() |
91 | 2) io_remap_pfn_range() or remap_pfn_range() or vm_insert_pfn() | 91 | 2) io_remap_pfn_range() or remap_pfn_range() or vm_insert_pfn() |
92 | 92 | ||
93 | With pat support, a new API pgprot_writecombine is being added. So, driver can | 93 | With PAT support, a new API pgprot_writecombine is being added. So, drivers can |
94 | continue to use the above sequence, with either pgprot_noncached() or | 94 | continue to use the above sequence, with either pgprot_noncached() or |
95 | pgprot_writecombine() in step 1, followed by step 2. | 95 | pgprot_writecombine() in step 1, followed by step 2. |
96 | 96 | ||
97 | In addition, step 2 internally tracks the region as UC or WC in memtype | 97 | In addition, step 2 internally tracks the region as UC or WC in memtype |
98 | list in order to ensure no conflicting mapping. | 98 | list in order to ensure no conflicting mapping. |
99 | 99 | ||
100 | Note that this set of APIs only work with IO (non RAM) regions. If driver | 100 | Note that this set of APIs only works with IO (non RAM) regions. If driver |
101 | wants to export RAM region, it has to do set_memory_uc() or set_memory_wc() | 101 | wants to export a RAM region, it has to do set_memory_uc() or set_memory_wc() |
102 | as step 0 above and also track the usage of those pages and use set_memory_wb() | 102 | as step 0 above and also track the usage of those pages and use set_memory_wb() |
103 | before the page is freed to free pool. | 103 | before the page is freed to free pool. |
104 | 104 | ||