Re: [PATCH v14 35/56] media: cedrus: Stop direct calls to queue num_buffers field

Paul Kocialkowski
2023-11-09T16:29:59Z

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Hi,

On Thu 09 Nov 23, 16:54, Benjamin Gaignard wrote:
>
> Le 09/11/2023 à 16:48, Andrzej Pietrasiewicz a écrit :
> > Hi Paul,
> >
> > W dniu 9.11.2023 o 15:14, Paul Kocialkowski pisze:
> > > Hi Andrzej,
> > >
> > > On Thu 09 Nov 23, 12:27, Andrzej Pietrasiewicz wrote:
> > > > Hi Paul,
> > > >
> > > > W dniu 31.10.2023 o 17:30, Benjamin Gaignard pisze:
> > > > > Use vb2_get_num_buffers() to avoid using queue num_buffers
> > > > > field directly.
> > > > > This allows us to change how the number of buffers is computed in the
> > > > > future.
> > > > >
> > > > > Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
> > > > > Acked-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
> > > >
> > > > Given you've alaredy A-b, would you be ok with adding this sentence:
> > > >
> > > > "While at it, check the return value of vb2_get_buffer()."
> > > >
> > > > to the commit message body?
> > >
> > > Not only do I agree, but because this is done in a function
> > > returning void,
> > > you could even:
> > >
> > > if (WARN_ON(!vb))
> > >     continue;
> > >
> > > so that it doesn't go completely unnoticed.
> > >
> > > What do you think?
> > >
> >
> > I'd ask Benjamin.
> >
> > But my take on the direction of changes is that ultimately
> > there will be "holes" in the array of allocated buffers (hence the
> > bitmap to track which slots are used and which are not). In other words,
> > getting a NULL sometimes will be an expected situation, and a WARN() will
> > not be appropriate for an expected situation.
> >
> > @Benjamin?
>
> That should never happens unless you add delete buffers capability to the driver
> and in this case it is normal to have holes.
> Other drivers do not use WARN_ON() so I will not do it for this one.

Yeah I also don't expect that buffers can just disappear on us before
introducing the delete buffers capability.

But okay it's fine with me to not use WARN_ON.

Cheers,

Paul

> Regards,
> Benjamin
>
> >
> > Regards,
> >
> > Andrzej
> >
> > > Cheers,
> > >
> > > Paul
> > >
> > > > @Benjamin:
> > > >
> > > > With this change, you can add my
> > > >
> > > > Reviewed-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> > > >
> > > > > CC: Maxime Ripard <mripard@kernel.org>
> > > > > ---
> > > > >    drivers/staging/media/sunxi/cedrus/cedrus_h264.c | 9 +++++++--
> > > > >    drivers/staging/media/sunxi/cedrus/cedrus_h265.c | 9 +++++++--
> > > > >    2 files changed, 14 insertions(+), 4 deletions(-)
> > > > >
> > > > > diff --git
> > > > > a/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> > > > > b/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> > > > > index dfb401df138a..3e2843ef6cce 100644
> > > > > --- a/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> > > > > +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h264.c
> > > > > @@ -653,8 +653,13 @@ static void cedrus_h264_stop(struct
> > > > > cedrus_ctx *ctx)
> > > > >        vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx,
> > > > > V4L2_BUF_TYPE_VIDEO_CAPTURE);
> > > > > -    for (i = 0; i < vq->num_buffers; i++) {
> > > > > -        buf = vb2_to_cedrus_buffer(vb2_get_buffer(vq, i));
> > > > > +    for (i = 0; i < vb2_get_num_buffers(vq); i++) {
> > > > > +        struct vb2_buffer *vb = vb2_get_buffer(vq, i);
> > > > > +
> > > > > +        if (!vb)
> > > > > +            continue;
> > > > > +
> > > > > +        buf = vb2_to_cedrus_buffer(vb);
> > > > >            if (buf->codec.h264.mv_col_buf_size > 0) {
> > > > >                dma_free_attrs(dev->dev,
> > > > > diff --git
> > > > > a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> > > > > b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> > > > > index fc9297232456..52e94c8f2f01 100644
> > > > > --- a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> > > > > +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
> > > > > @@ -869,8 +869,13 @@ static void cedrus_h265_stop(struct
> > > > > cedrus_ctx *ctx)
> > > > >        vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx,
> > > > > V4L2_BUF_TYPE_VIDEO_CAPTURE);
> > > > > -    for (i = 0; i < vq->num_buffers; i++) {
> > > > > -        buf = vb2_to_cedrus_buffer(vb2_get_buffer(vq, i));
> > > > > +    for (i = 0; i < vb2_get_num_buffers(vq); i++) {
> > > > > +        struct vb2_buffer *vb = vb2_get_buffer(vq, i);
> > > > > +
> > > > > +        if (!vb)
> > > > > +            continue;
> > > > > +
> > > > > +        buf = vb2_to_cedrus_buffer(vb);
> > > > >            if (buf->codec.h265.mv_col_buf_size > 0) {
> > > > >                dma_free_attrs(dev->dev,
> > > >
> > >
> > >
> > > _______________________________________________
> > > Kernel mailing list -- kernel@mailman.collabora.com
> > > To unsubscribe send an email to kernel-leave@mailman.collabora.com
> >

--
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com

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