linux-kernel - Re: [PATCH] media: verisilicon: Explicitly disable all encoder ioctls for decoders

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Message-ID: <aK8uRrlbMWZsA88Q@shepard>
Date: Wed, 27 Aug 2025 18:11:50 +0200
From: Paul Kocialkowski <paulk@...-base.io>
To: Nicolas Dufresne <nicolas.dufresne@...labora.com>
Cc: linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Benjamin Gaignard <benjamin.gaignard@...labora.com>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Mauro Carvalho Chehab <mchehab@...nel.org>
Subject: Re: [PATCH] media: verisilicon: Explicitly disable all encoder
 ioctls for decoders

Hi Nicolas,

On Wed 27 Aug 25, 10:30, Nicolas Dufresne wrote:
> Hi Paul,
> 
> Le mardi 26 août 2025 à 21:04 +0200, Paul Kocialkowski a écrit :
> > Call the dedicated v4l2_disable_ioctl helper instead of manually
> > checking whether the current context is an encoder for the selection
> > ioctls.
> > 
> > Signed-off-by: Paul Kocialkowski <paulk@...-base.io>
> > ---
> >  drivers/media/platform/verisilicon/hantro_drv.c  | 2 ++
> >  drivers/media/platform/verisilicon/hantro_v4l2.c | 6 ++----
> >  2 files changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/media/platform/verisilicon/hantro_drv.c
> > b/drivers/media/platform/verisilicon/hantro_drv.c
> > index 4cc9d00fd293..6fb28a6293e7 100644
> > --- a/drivers/media/platform/verisilicon/hantro_drv.c
> > +++ b/drivers/media/platform/verisilicon/hantro_drv.c
> > @@ -916,6 +916,8 @@ static int hantro_add_func(struct hantro_dev *vpu,
> > unsigned int funcid)
> >  		vpu->decoder = func;
> >  		v4l2_disable_ioctl(vfd, VIDIOC_TRY_ENCODER_CMD);
> >  		v4l2_disable_ioctl(vfd, VIDIOC_ENCODER_CMD);
> > +		v4l2_disable_ioctl(vfd, VIDIOC_G_SELECTION);
> > +		v4l2_disable_ioctl(vfd, VIDIOC_S_SELECTION);
> 
> Disabling this IOCTL for JPEG is fine, but for VP8, H.264, HEVC, VP9 and AV1, it
> is pretty much mandatory. Otherwise your stream will advertise the padded
> dimentions and there would be no way to tell it that what is the cropping window
> for bitstream generation purpose.

Maybe the lack of context around the patch doesn't make it clear, but this is
to disable the ioctls for decoders (not encoders), which don't need to use the
selection API. This keeps the ioctls enabled and available for all encoders.

> Considering you are looking forward adding H.264 encoding, do you really want
> to apply this fix ?

I am well aware that this is required to setup the crop in the coded bitstream
and I am definitely using it in my encoding work :)

Cheers,

Paul

> 
> Nicolas
> 
> >  	}
> >  
> >  	video_set_drvdata(vfd, vpu);
> > diff --git a/drivers/media/platform/verisilicon/hantro_v4l2.c
> > b/drivers/media/platform/verisilicon/hantro_v4l2.c
> > index 6bcd892e7bb4..fcf3bd9bcda2 100644
> > --- a/drivers/media/platform/verisilicon/hantro_v4l2.c
> > +++ b/drivers/media/platform/verisilicon/hantro_v4l2.c
> > @@ -663,8 +663,7 @@ static int vidioc_g_selection(struct file *file, void
> > *priv,
> >  	struct hantro_ctx *ctx = file_to_ctx(file);
> >  
> >  	/* Crop only supported on source. */
> > -	if (!ctx->is_encoder ||
> > -	    sel->type != V4L2_BUF_TYPE_VIDEO_OUTPUT)
> > +	if (sel->type != V4L2_BUF_TYPE_VIDEO_OUTPUT)
> >  		return -EINVAL;
> >  
> >  	switch (sel->target) {
> > @@ -696,8 +695,7 @@ static int vidioc_s_selection(struct file *file, void
> > *priv,
> >  	struct vb2_queue *vq;
> >  
> >  	/* Crop only supported on source. */
> > -	if (!ctx->is_encoder ||
> > -	    sel->type != V4L2_BUF_TYPE_VIDEO_OUTPUT)
> > +	if (sel->type != V4L2_BUF_TYPE_VIDEO_OUTPUT)
> >  		return -EINVAL;
> >  
> >  	/* Change not allowed if the queue is streaming. */



-- 
Paul Kocialkowski,

Independent contractor - sys-base - https://www.sys-base.io/
Free software developer - https://www.paulk.fr/

Expert in multimedia, graphics and embedded hardware support with Linux.

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