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authorvenkatesh.pallipadi@intel.com <venkatesh.pallipadi@intel.com>2008-12-19 16:47:30 -0500
committerH. Peter Anvin <hpa@zytor.com>2008-12-19 18:40:31 -0500
commit67bac792cd0c05b4b6e0393c32605b028b8dd533 (patch)
tree03e978a671180abbd634e40add6a29b1887334ca /Documentation/x86/pat.txt
parent34801ba9bf0381fcf0e2b08179d2c07f2c6ede74 (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.txt10
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
83Advanced APIs for drivers 83Advanced APIs for drivers
84------------------------- 84-------------------------
85A. Exporting pages to user with remap_pfn_range, io_remap_pfn_range, 85A. Exporting pages to users with remap_pfn_range, io_remap_pfn_range,
86vm_insert_pfn 86vm_insert_pfn
87 87
88Drivers wanting to export some pages to userspace, do it by using mmap 88Drivers wanting to export some pages to userspace do it by using mmap
89interface and a combination of 89interface and a combination of
901) pgprot_noncached() 901) pgprot_noncached()
912) io_remap_pfn_range() or remap_pfn_range() or vm_insert_pfn() 912) io_remap_pfn_range() or remap_pfn_range() or vm_insert_pfn()
92 92
93With pat support, a new API pgprot_writecombine is being added. So, driver can 93With PAT support, a new API pgprot_writecombine is being added. So, drivers can
94continue to use the above sequence, with either pgprot_noncached() or 94continue to use the above sequence, with either pgprot_noncached() or
95pgprot_writecombine() in step 1, followed by step 2. 95pgprot_writecombine() in step 1, followed by step 2.
96 96
97In addition, step 2 internally tracks the region as UC or WC in memtype 97In addition, step 2 internally tracks the region as UC or WC in memtype
98list in order to ensure no conflicting mapping. 98list in order to ensure no conflicting mapping.
99 99
100Note that this set of APIs only work with IO (non RAM) regions. If driver 100Note that this set of APIs only works with IO (non RAM) regions. If driver
101wants to export RAM region, it has to do set_memory_uc() or set_memory_wc() 101wants to export a RAM region, it has to do set_memory_uc() or set_memory_wc()
102as step 0 above and also track the usage of those pages and use set_memory_wb() 102as step 0 above and also track the usage of those pages and use set_memory_wb()
103before the page is freed to free pool. 103before the page is freed to free pool.
104 104