Messages in this thread Patch in this message | | | Date | Thu, 18 Dec 2008 13:49:41 -0800 | From | "Pallipadi, Venkatesh" <> | Subject | Re: [patch 7/7] x86 PAT: update documentation to cover pgprot and remap_pfn related changes - v3 |
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On Thu, Dec 18, 2008 at 01:13:28PM -0800, Randy Dunlap wrote: > venkatesh.pallipadi@intel.com wrote: > > +Advanced APIs for drivers > +------------------------- > +A. Exporting pages to user with remap_pfn_range, io_remap_pfn_range, > > to users > or to userspace > > +vm_insert_pfn > + > +Drivers wanting to export some pages to userspace, do it by using mmap > > Drop comma. > > +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 > > s/pat/PAT/ > s/driver/drivers/ or s/driver/a driver/ > > +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 > > works with IO (non-RAM) regions. If a driver > > +wants to export RAM region, it has to do set_memory_uc() or set_memory_wc() > > export a RAM region, > > +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. > >
refreshed patch below
Thanks, Venki
Add documentation related to pgprot_* change.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> --- Documentation/x86/pat.txt | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+)
Index: linux-2.6/Documentation/x86/pat.txt =================================================================== --- linux-2.6.orig/Documentation/x86/pat.txt 2008-12-17 15:01:50.000000000 -0800 +++ linux-2.6/Documentation/x86/pat.txt 2008-12-17 17:23:16.000000000 -0800 @@ -80,6 +80,30 @@ pci proc | -- | - | | | | ------------------------------------------------------------------- +Advanced APIs for drivers +------------------------- +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 +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, 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 a 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. + + + Notes: -- in the above table mean "Not suggested usage for the API". Some of the --'s
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