Re: [PATCH v17 8/8] media: verisilicon: Support deleting buffers on capture queue

[Benjamin Gaignard]

Le 24/01/2024 à 16:44, Hans Verkuil a écrit :
> On 24/01/2024 16:35, Benjamin Gaignard wrote:
> > Le 24/01/2024 à 13:52, Hans Verkuil a écrit :
> > > On 19/01/2024 10:49, Benjamin Gaignard wrote:
> > > > Allow to delete buffers on capture queue because it the one which
> > > > own the decoded buffers. After a dynamic resolution change lot of
> > > > them could remain allocated but won't be used anymore so deleting
> > > > them save memory.
> > > > Do not add this feature on output queue because the buffers are
> > > > smaller, fewer and always recycled even after a dynamic resolution
> > > > change.
> > > >
> > > > Signed-off-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxxxxx>
> > > > ---
> > > >    drivers/media/platform/verisilicon/hantro_drv.c  | 1 +
> > > >    drivers/media/platform/verisilicon/hantro_v4l2.c | 1 +
> > > >    2 files changed, 2 insertions(+)
> > > >
> > > > diff --git a/drivers/media/platform/verisilicon/hantro_drv.c b/drivers/media/platform/verisilicon/hantro_drv.c
> > > > index db3df6cc4513..f6b0a676a740 100644
> > > > --- a/drivers/media/platform/verisilicon/hantro_drv.c
> > > > +++ b/drivers/media/platform/verisilicon/hantro_drv.c
> > > > @@ -248,6 +248,7 @@ queue_init(void *priv, struct vb2_queue *src_vq, struct vb2_queue *dst_vq)
> > > >        dst_vq->timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_COPY;
> > > >        dst_vq->lock = &ctx->dev->vpu_mutex;
> > > >        dst_vq->dev = ctx->dev->v4l2_dev.dev;
> > > > +    src_vq->supports_delete_bufs = true;
> > > As I mentioned, I remain unconvinced by this. It is just making the API inconsistent
> > > since if you support delete_bufs, then why support it for one queue only and not both?
> > Because the both queues don't handle the same type of data.
> > For example for a stateless decoder, for me, it makes sense to allow delete decoded frames
> > if they won't be used anymore but that won't makes sense for bitstream buffers.
> But is there any reason why you wouldn't support this feature? We support VIDIOC_CREATE_BUFS
> as well, even though most drivers do not need it, but it is cheap to add.
>
> Deleting buffers is a generic feature, and I don't see why you wouldn't just offer it
> for both queues.

You want me to remove supports_delete_bufs and V4L2_BUF_CAP_SUPPORTS_DELETE_BUFS ?
This way we can remove buffers from the both queues.
Sound good for you ?

Regards,
Benjamin

> Regards,
>
> 	Hans
>
> > > >          return vb2_queue_init(dst_vq);
> > > >    }
> > > > diff --git a/drivers/media/platform/verisilicon/hantro_v4l2.c b/drivers/media/platform/verisilicon/hantro_v4l2.c
> > > > index 941fa23c211a..34eab90e8a42 100644
> > > > --- a/drivers/media/platform/verisilicon/hantro_v4l2.c
> > > > +++ b/drivers/media/platform/verisilicon/hantro_v4l2.c
> > > > @@ -756,6 +756,7 @@ const struct v4l2_ioctl_ops hantro_ioctl_ops = {
> > > >        .vidioc_dqbuf = v4l2_m2m_ioctl_dqbuf,
> > > >        .vidioc_prepare_buf = v4l2_m2m_ioctl_prepare_buf,
> > > >        .vidioc_create_bufs = v4l2_m2m_ioctl_create_bufs,
> > > > +    .vidioc_delete_bufs = v4l2_m2m_ioctl_delete_bufs,
> > > >        .vidioc_expbuf = v4l2_m2m_ioctl_expbuf,
> > > >          .vidioc_subscribe_event = v4l2_ctrl_subscribe_event,
> > > In my view setting vidioc_delete_bufs should enable this feature, and if
> > > for some strange reason only one queue support it, then make a wrapper
> > > callback that returns an error when used with the wrong queue.
> > >
> > > Also note that patch 6/8 never checks for q->supports_delete_bufs in
> > > vb2_core_delete_bufs(), which is wrong!
> > I will fix that in next version.
> > Regards,
> > Benjamin
> >
> > > Regards,
> > >
> > >      Hans