linux-kernel - Re: [PATCH 01/10] media: ioctl: Simulate v4l2_queryctrl with v4l2_query_ext

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Message-ID: <4bd4796f-858a-48f7-9b32-ef6991ebe194@xs4all.nl>
Date: Mon, 9 Dec 2024 20:34:46 +0100
From: Hans Verkuil <hverkuil@...all.nl>
To: Ricardo Ribalda <ribalda@...omium.org>,
 Mauro Carvalho Chehab <mchehab@...nel.org>, Mike Isely <isely@...ox.com>,
 Laurent Pinchart <laurent.pinchart@...asonboard.com>,
 Hans de Goede <hdegoede@...hat.com>,
 Sakari Ailus <sakari.ailus@...ux.intel.com>,
 Andy Shevchenko <andy@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-staging@...ts.linux.dev
Subject: Re: [PATCH 01/10] media: ioctl: Simulate v4l2_queryctrl with
 v4l2_query_ext_ctrl

On 09/12/2024 20:25, Ricardo Ribalda wrote:
> v4l2_queryctrl is a subset of v4l2_query_ext_ctrl. If the driver does
> not implement v4l2_queryctrl we can implement it with
> v4l2_query_ext_ctrl.
> 
> Suggested-by: Hans de Goede <hdegoede@...hat.com>
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> ---
>  drivers/media/v4l2-core/v4l2-dev.c   |  3 ++-
>  drivers/media/v4l2-core/v4l2-ioctl.c | 22 +++++++++++++++++++++-
>  2 files changed, 23 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
> index 5bcaeeba4d09..252308a67fa8 100644
> --- a/drivers/media/v4l2-core/v4l2-dev.c
> +++ b/drivers/media/v4l2-core/v4l2-dev.c
> @@ -572,7 +572,8 @@ static void determine_valid_ioctls(struct video_device *vdev)
>  	   and that can't be tested here. If the bit for these control ioctls
>  	   is set, then the ioctl is valid. But if it is 0, then it can still
>  	   be valid if the filehandle passed the control handler. */
> -	if (vdev->ctrl_handler || ops->vidioc_queryctrl)
> +	if (vdev->ctrl_handler || ops->vidioc_queryctrl ||
> +	    ops->vidioc_query_ext_ctrl)
>  		__set_bit(_IOC_NR(VIDIOC_QUERYCTRL), valid_ioctls);
>  	if (vdev->ctrl_handler || ops->vidioc_query_ext_ctrl)
>  		__set_bit(_IOC_NR(VIDIOC_QUERY_EXT_CTRL), valid_ioctls);
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index 0304daa8471d..a5562f2f1fc9 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -2284,9 +2284,11 @@ static int v4l_queryctrl(const struct v4l2_ioctl_ops *ops,
>  				struct file *file, void *fh, void *arg)
>  {
>  	struct video_device *vfd = video_devdata(file);
> +	struct v4l2_query_ext_ctrl qec;
>  	struct v4l2_queryctrl *p = arg;
>  	struct v4l2_fh *vfh =
>  		test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags) ? fh : NULL;
> +	int ret;
>  
>  	if (vfh && vfh->ctrl_handler)
>  		return v4l2_queryctrl(vfh->ctrl_handler, p);
> @@ -2294,7 +2296,25 @@ static int v4l_queryctrl(const struct v4l2_ioctl_ops *ops,
>  		return v4l2_queryctrl(vfd->ctrl_handler, p);
>  	if (ops->vidioc_queryctrl)
>  		return ops->vidioc_queryctrl(file, fh, p);
> -	return -ENOTTY;
> +	if (!ops->vidioc_query_ext_ctrl)
> +		return -ENOTTY;
> +
> +	/* Simulate query_ext_ctr using query_ctrl. */
> +	qec.id = p->id;
> +	ret = ops->vidioc_query_ext_ctrl(file, fh, &qec);
> +	if (ret)
> +		return ret;
> +
> +	p->id = qec.id;
> +	p->type = qec.type;
> +	strscpy(p->name, qec.name, sizeof(p->name));
> +	p->minimum = qec.minimum;
> +	p->maximum = qec.maximum;
> +	p->step = qec.step;
> +	p->default_value = qec.default_value;
> +	p->flags = qec.flags;

That's not quite correct. See v4l2_queryctrl() in v4l2-ctrls-api.c
on how to do this: for types that VIDIOC_QUERYCTRL doesn't support,
some of these fields must be set to 0.

In fact, once vidioc_queryctrl has been removed, then you can also
remove v4l2_queryctrl() and just rely on this code. Unless I missed
something.

Regards,

	Hans

> +
> +	return 0;
>  }
>  
>  static int v4l_query_ext_ctrl(const struct v4l2_ioctl_ops *ops,
>