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    SubjectRe: [PATCH v5 00/39] i.MX Media Driver
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    On 03/21/17 11:42, Niklas Söderlund wrote:
    > On 2017-03-20 16:57:54 +0100, Hans Verkuil wrote:
    >> On 03/20/2017 03:11 PM, Russell King - ARM Linux wrote:
    >>> On Mon, Mar 20, 2017 at 02:57:03PM +0100, Hans Verkuil wrote:
    >>>> On 03/20/2017 02:29 PM, Russell King - ARM Linux wrote:
    >>>>> It's what I have - remember, not everyone is happy to constantly replace
    >>>>> their distro packages with random new stuff.
    >>>>
    >>>> This is a compliance test, which is continuously developed in tandem with
    >>>> new kernel versions. If you are working with an upstream kernel, then you
    >>>> should also use the corresponding v4l2-compliance test. What's the point
    >>>> of using an old one?
    >>>>
    >>>> I will not support driver developers that use an old version of the
    >>>> compliance test, that's a waste of my time.
    >>>
    >>> The reason that people may _not_ wish to constantly update v4l-utils
    >>> is that it changes the libraries installed on their systems.
    >>>
    >>> So, the solution to that is not to complain about developers not using
    >>> the latest version, but instead to de-couple it from the rest of the
    >>> package, and provide it as a separate, stand-alone package that doesn't
    >>> come with all the extra baggage.
    >>>
    >>> Now, there's two possible answers to that:
    >>>
    >>> 1. it depends on the libv4l2 version. If that's so, then you are
    >>> insisting that people constantly move to the latest libv4l2 because
    >>> of API changes, and those API changes may upset applications they're
    >>> using. So this isn't really on.
    >>>
    >>> 2. it doesn't depend on libv4l2 version, in which case there's no reason
    >>> for it to be packaged with v4l-utils.
    >>
    >> Run configure with --disable-v4l2-compliance-libv4l.
    >>
    >> This avoids linking with libv4l and allows you to build it stand-alone.
    >>
    >> Perhaps I should invert this option since in most cases you don't want to
    >> run v4l2-compliance with libv4l (it's off by default unless you pass the
    >> -w option to v4l2-compliance).
    >>
    >>>
    >>> The reality is that v4l2-compliance links with libv4l2, so I'm not sure
    >>> which it is. What I am sure of is that I don't want to upgrade libv4l2
    >>> on an ad-hoc basis, potentially causing issues with applications.
    >>>
    >>>>>> To test actual streaming you need to provide the -s option.
    >>>>>>
    >>>>>> Note: v4l2-compliance has been developed for 'regular' video devices,
    >>>>>> not MC devices. It may or may not work with the -s option.
    >>>>>
    >>>>> Right, and it exists to verify that the establised v4l2 API is correctly
    >>>>> implemented. If the v4l2 API is being offered to user applications,
    >>>>> then it must be conformant, otherwise it's not offering the v4l2 API.
    >>>>> (That's very much a definition statement in itself.)
    >>>>>
    >>>>> So, are we really going to say MC devices do not offer the v4l2 API to
    >>>>> userspace, but something that might work? We've already seen today
    >>>>> one user say that they're not going to use mainline because of the
    >>>>> crud surrounding MC.
    >>>>>
    >>>>
    >>>> Actually, my understanding was that he was stuck on the old kernel code.
    >>>
    >>> Err, sorry, I really don't follow. Who is "he"?
    >>
    >> "one user say that they're not going to use mainline because of the
    >> crud surrounding MC."
    >>
    >>>
    >>> _I_ was the one who reported the EXPBUF problem. Your comment makes no
    >>> sense.
    >>>
    >>>> In the case of v4l2-compliance, I never had the time to make it work with
    >>>> MC devices. Same for that matter of certain memory to memory devices.
    >>>>
    >>>> Just like MC devices these too behave differently. They are partially
    >>>> supported in v4l2-compliance, but not fully.
    >>>
    >>> It seems you saying that the API provided by /dev/video* for a MC device
    >>> breaks the v4l2-compliance tests?
    >>
    >> There may be tests in the compliance suite that do not apply for MC devices
    >> and for which I never check. The compliance suite was never written with MC
    >> devices in mind, and it certainly hasn't been tested much with such devices.
    >>
    >> It's only very recent that I even got hardware that has MC support...
    >>
    >> From what I can tell from the feedback I got it seems to be OKish, but I
    >> just can't guarantee that the compliance utility is correct for such devices.
    >>
    >> In particular I doubt the streaming tests (-s, -f, etc.) will work. The -s
    >> test *might* work if the pipeline is configured correctly before running
    >> v4l2-compliance. I can't imagine that the -f option would work at all since
    >> I would expect pipeline validation errors.
    >
    > I successfully use v4l2-compliance with the -s option to test the
    > Renesas R-Car Gen3 driver which uses MC, I first have to setup the
    > pipeline using media-ctl. I have had much use of the tool and it have
    > helped me catch many errors in the rcar-vin driver both on Gen2 (no MC
    > involved) and Gen3. And yes the -f option is only usable on Gen2 where
    > MC is not used.

    Ah, good to hear that -s works with MC. I was not sure about that.
    Thanks for the feedback!

    Regards,

    Hans

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