Re: [patch 7/7] x86 PAT: update documentation to cover pgprot and remap_pfn related changes - v3

Randy Dunlap
2008-12-18T21:16:25Z

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.

--
~Randy