linux-kernel - RE: [patch 7/7] x86 PAT: update documentation to cover pgprot and remap_pfn related changes

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Date:	Thu, 18 Dec 2008 14:03:18 -0800
From:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
To:	Randy Dunlap <randy.dunlap@...cle.com>
CC:	"mingo@...e.hu" <mingo@...e.hu>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"hpa@...or.com" <hpa@...or.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"npiggin@...e.de" <npiggin@...e.de>,
	"hugh@...itas.com" <hugh@...itas.com>,
	"arjan@...radead.org" <arjan@...radead.org>,
	"jbarnes@...tuousgeek.org" <jbarnes@...tuousgeek.org>,
	"rdreier@...co.com" <rdreier@...co.com>,
	"jeremy@...p.org" <jeremy@...p.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
Subject: RE: [patch 7/7] x86 PAT: update documentation to cover pgprot and
 remap_pfn related changes - v3

 

>-----Original Message-----
>From: Randy Dunlap [mailto:randy.dunlap@...cle.com] 
>Sent: Thursday, December 18, 2008 1:53 PM
>To: Pallipadi, Venkatesh
>Cc: mingo@...e.hu; tglx@...utronix.de; hpa@...or.com; 
>akpm@...ux-foundation.org; npiggin@...e.de; hugh@...itas.com; 
>arjan@...radead.org; jbarnes@...tuousgeek.org; 
>rdreier@...co.com; jeremy@...p.org; 
>linux-kernel@...r.kernel.org; Siddha, Suresh B
>Subject: Re: [patch 7/7] x86 PAT: update documentation to 
>cover pgprot and remap_pfn related changes - v3
>
>Pallipadi, Venkatesh wrote:
>> On Thu, Dec 18, 2008 at 01:13:28PM -0800, Randy Dunlap wrote:
>>> venkatesh.pallipadi@...el.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
>
>Some of them were changed, others not changed, with no explanation...
>More changes below:

Sorry. Not sure how I missed it :( (note to self - do not send
patches soon after lunch). Will promise to do all the changes
as an incremental patch along with other comments.

Thanks,
Venki

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