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SubjectRe: [PATCH v2 for 5.4 1/4] media: hantro: Fix s_fmt for dynamic resolution changes
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Hi Hans,

On Sat, 2019-11-09 at 13:25 +0100, Hans Verkuil wrote:
> On 11/8/19 11:19 AM, Boris Brezillon wrote:
> > On Mon, 7 Oct 2019 14:45:02 -0300
> > Ezequiel Garcia <ezequiel@collabora.com> wrote:
> >
> > > Commit 953aaa1492c53 ("media: rockchip/vpu: Prepare things to support decoders")
> > > changed the conditions under S_FMT was allowed for OUTPUT
> > > CAPTURE buffers.
> > >
> > > However, and according to the mem-to-mem stateless decoder specification,
> > > in order to support dynamic resolution changes, S_FMT should be allowed
> > > even if OUTPUT buffers have been allocated.
> > >
> > > Relax decoder S_FMT restrictions on OUTPUT buffers, allowing a resolution
> > > modification, provided the pixel format stays the same.
> > >
> > > Tested on RK3288 platforms using ChromiumOS Video Decode/Encode Accelerator Unittests.
> > >
> > > Fixes: 953aaa1492c53 ("media: rockchip/vpu: Prepare things to support decoders")
> > > Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
> > > --
> > > v2:
> > > * Call try_fmt_out before using the format,
> > > pointed out by Philipp.
> > >
> > > drivers/staging/media/hantro/hantro_v4l2.c | 28 +++++++++++++++-------
> > > 1 file changed, 19 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/drivers/staging/media/hantro/hantro_v4l2.c b/drivers/staging/media/hantro/hantro_v4l2.c
> > > index 3dae52abb96c..586d243cc3cc 100644
> > > --- a/drivers/staging/media/hantro/hantro_v4l2.c
> > > +++ b/drivers/staging/media/hantro/hantro_v4l2.c
> > > @@ -367,19 +367,26 @@ vidioc_s_fmt_out_mplane(struct file *file, void *priv, struct v4l2_format *f)
> > > {
> > > struct v4l2_pix_format_mplane *pix_mp = &f->fmt.pix_mp;
> > > struct hantro_ctx *ctx = fh_to_ctx(priv);
> > > + struct vb2_queue *vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx, f->type);
> > > const struct hantro_fmt *formats;
> > > unsigned int num_fmts;
> > > - struct vb2_queue *vq;
> > > int ret;
> > >
> > > - /* Change not allowed if queue is busy. */
> > > - vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx, f->type);
> > > - if (vb2_is_busy(vq))
> > > - return -EBUSY;
> > > + ret = vidioc_try_fmt_out_mplane(file, priv, f);
> > > + if (ret)
> > > + return ret;
> > >
> > > if (!hantro_is_encoder_ctx(ctx)) {
> > > struct vb2_queue *peer_vq;
> > >
> > > + /*
> > > + * In other to support dynamic resolution change,
> >
> > ^ order
> >
> > > + * the decoder admits a resolution change, as long
> > > + * as the pixelformat remains. Can't be done if streaming.
> > > + */
> > > + if (vb2_is_streaming(vq) || (vb2_is_busy(vq) &&
> > > + pix_mp->pixelformat != ctx->src_fmt.pixelformat))
> > > + return -EBUSY;
> >
> > Sorry to chime in only now, but I'm currently looking at the VP9 spec
> > and it seems the resolution is allowed to change dynamically [1] (I
> > guess the same applies to VP8). IIU the spec correctly, coded frames
> > using the new resolution can reference decoded frames using the old
> > one (can be higher or lower res BTW). If we force a streamoff to change
> > the resolution (as seems to be the case here), we'll lose those ref
> > frames (see the hantro_return_bufs() in stop streaming), right?
> > Hans, Tomasz, any idea how this dynamic resolution change could/should
> > be supported?
>
> As Tomasz also mentioned, supporting this is much more work, and probably
> requires new streaming ioctls.
>
> In the meantime I think this patch is fine (with the typo fixed, I can do
> that), so is it OK if I merge this?
>

Yes, please.

I originally posted this as a v5.4 fix, so it would be nice
if we can mark this as stable material.

Thanks,
Ezequiel

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