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SubjectRe: [EXT] Re: [PATCH 0/5] Add V4L2 driver for i.MX8 JPEG Encoder/Decoder
Hi Hans,

On Mi, 2019-11-06 at 17:52 +0100, Hans Verkuil wrote:
>       test Scaling: OK
> The presence of a scaler is suspicious: is the encoder indeed
> capable of scaling? I suspect this is a bug.

No, it's not capable of scaling. You suspect a bug in the driver or the

> Codec ioctls:
> >       test VIDIOC_(TRY_)ENCODER_CMD: OK
> The presence of this...
> >
> >       test VIDIOC_G_ENC_INDEX: OK (Not Supported)
> >       test VIDIOC_(TRY_)DECODER_CMD: OK
> ...and this is also strange for a JPEG codec. These ioctls are
> typically only
> needed for MPEG/H264/etc. codecs, and not for a simple JPEG codec.
> The same issues are found for the JPEG decoder.

I implemented the CMD_STOP for both encoder & decoder, because it was
requested by our developer for gstreamer plugin for this codec.
The context in which this was requested was for playing MJPEG videos (a
concatenation of JPEG frames).

> Streaming ioctls:
> >       test read/write: OK (Not Supported)
> >       test blocking wait: OK
> >               fail: v4l2-test-buffers.cpp(254): g_field() ==
> The driver shall never return FIELD_ANY. This needs to be FIELD_NONE.

Is there a "good example" of a v4l m2m driver that passes these
streaming tests? That would save some time on my side.
For the FIELD_ANY issue, I got inspired from your commit:
ab7afaf3 media: vim2m: add buf_out_validate callback
But there's a lot more to go...

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