linux-kernel - Re: [PATCHv4 01/11] videobuf2: add cache management members

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Date:   Mon, 9 Mar 2020 08:28:09 +0100
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Sergey Senozhatsky <senozhatsky@...omium.org>
Cc:     Hans Verkuil <hans.verkuil@...co.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Sakari Ailus <sakari.ailus@....fi>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Pawel Osciak <posciak@...omium.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [PATCHv4 01/11] videobuf2: add cache management members

On 3/9/20 8:25 AM, Sergey Senozhatsky wrote:
> On (20/03/09 08:21), Hans Verkuil wrote:
>> On 3/9/20 4:27 AM, Sergey Senozhatsky wrote:
>>> On (20/03/07 12:47), Hans Verkuil wrote:
>>>>
>>>> Create those tests in v4l2-compliance: that's where they belong.
>>>>
>>>> You need these tests:
>>>>
>>>> For non-MMAP modes:
>>>>
>>>> 1) test that V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS is never set.
>>>>
>>>> If V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS is not set, then:
>>>>
>>>> 1) attempting to use V4L2_FLAG_MEMORY_NON_CONSISTENT will clear the flag
>>>>    upon return (test with both reqbufs and create_bufs).
>>>> 2) attempting to use V4L2_BUF_FLAG_NO_CACHE_INVALIDATE or V4L2_BUF_FLAG_NO_CACHE_CLEAN
>>>>    will clear those flags upon return (do we actually do that in the patch series?).
> 
> [..]
> 
>>> I'm looking into it. Will it work if I patch the vivid test driver to
>>> enable/disable ->allow_cache_hints bit per-node and include the patch
>>> into the series. So then v4l2 tests can create some nodes with
>>> ->allow_cache_hints.  Something like this:
>>
>> I would add a 'cache_hints' module parameter (array of bool) to tell vivid
>> whether cache hints should be set or not for each instance. It would be useful
>> to have this in vivid. Don't forget to update Documentation/media/v4l-drivers/vivid.rst
>> as well.
> 
> I see. Hmm, how do I do "test that V4L2_BUF_CAP_SUPPORTS_CACHE_HINTS
> is never set" then?

Not sure I understand your question. When requesting buffers for non-MMAP memory,
this capability must never be returned. That has nothing to do with a cache_hints
module option.

Regards,

	Hans

> 
> 	-ss
>