Re: [PATCH 0/9 v2] Helper to abstract vma handling in media layer

[Hans Verkuil <hverkuil@xs4all.nl>]

Hi Marek,

On 04/24/2015 12:59 PM, Marek Szyprowski wrote:
> Dear All,
> 
> On 2015-04-02 17:25, Hans Verkuil wrote:
>> On 04/02/2015 05:02 PM, Jan Kara wrote:
>>>    Hello,
>>>
>>> On Tue 17-03-15 12:56:30, Jan Kara wrote:
>>>>    After a long pause I'm sending second version of my patch series to abstract
>>>> vma handling from the various media drivers. After this patch set drivers have
>>>> to know much less details about vmas, their types, and locking. My motivation
>>>> for the series is that I want to change get_user_pages() locking and I want to
>>>> handle subtle locking details in as few places as possible.
>>>>
>>>> The core of the series is the new helper get_vaddr_pfns() which is given a
>>>> virtual address and it fills in PFNs into provided array. If PFNs correspond to
>>>> normal pages it also grabs references to these pages. The difference from
>>>> get_user_pages() is that this function can also deal with pfnmap, mixed, and io
>>>> mappings which is what the media drivers need.
>>>>
>>>> I have tested the patches with vivid driver so at least vb2 code got some
>>>> exposure. Conversion of other drivers was just compile-tested so I'd like to
>>>> ask respective maintainers if they could have a look.  Also I'd like to ask mm
>>>> folks to check patch 2/9 implementing the helper. Thanks!
>>>    Ping? Any reactions?
>> For patch 1/9:
>>
>> Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
>>
>> For the other patches I do not feel qualified to give Acks. I've Cc-ed Pawel and
>> Marek who have a better understanding of the mm internals than I do. Hopefully
>> they can review the code.
>>
>> It definitely looks like a good idea, and if nobody else will comment on the vb2
>> patches in the next 2 weeks, then I'll try to review it myself (for whatever that's
>> worth).
> 
> I'm really sorry that I didn't manage to find time to review this 
> patchset. I really
> like the idea of moving pfn lookup from videobuf2/driver to some common 
> code in mm
> and it is really great that someone managed to provide nice generic code 
> for it.
> 
> I've applied the whole patchset onto v4.0 and tested it on Odroid U3 
> (with some
> additional patches). VideoBuf2-dc works still fine with USERPTR gathered 
> from other's
> device mmaped buffer. You can add my:
> 
> Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

Thanks!

> 
> for the patches 1-8. Patch 9/9 doesn't apply anymore, so I've skipped 
> it. Patch 2
> needs a small fixup - you need to add '#include <linux/vmalloc.h>', 
> because otherwise
> it doesn't compile. There have been also a minor conflict to be resolved 
> in patch 7.

I've just added patch 1/9 to my pull request for 4.2. But for patch 2/9 I need
Acks from the mm maintainers. I think it makes sense if patches 2-8 all go
in together via the linux-media tree. Jan, can you reach out to the right
devs to get Acks?

Regards,

	Hans

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