linux-kernel - Re: [PATCH v5 01/13] media: v4l2-ioctl: Fix check_ext

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Date:   Wed, 17 Mar 2021 11:36:31 +0100
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     Ricardo Ribalda <ribalda@...omium.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        tfiga@...omium.org
Cc:     stable@...r.kernel.org
Subject: Re: [PATCH v5 01/13] media: v4l2-ioctl: Fix check_ext_ctrls

On 16/03/2021 18:59, Ricardo Ribalda wrote:
> Drivers that do not use the ctrl-framework use this function instead.
> 
> - Return error when handling of REQUEST_VAL.
> - Do not check for multiple classes when getting the DEF_VAL.
> 
> Fixes v4l2-compliance:
> Control ioctls (Input 0):
> 		fail: v4l2-test-controls.cpp(813): doioctl(node, VIDIOC_G_EXT_CTRLS, &ctrls)
> 	test VIDIOC_G/S/TRY_EXT_CTRLS: FAIL
> 
> Cc: stable@...r.kernel.org
> Fixes: 6fa6f831f095 ("media: v4l2-ctrls: add core request support")
> Suggested-by: Hans Verkuil <hverkuil-cisco@...all.nl>
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> ---
>  drivers/media/v4l2-core/v4l2-ioctl.c | 25 +++++++++++++++++--------
>  1 file changed, 17 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index 31d1342e61e8..9406e90ff805 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -917,15 +917,24 @@ static int check_ext_ctrls(struct v4l2_ext_controls *c, int allow_priv)

allow_priv really should be a bool.

>  	for (i = 0; i < c->count; i++)
>  		c->controls[i].reserved2[0] = 0;
>  
> -	/* V4L2_CID_PRIVATE_BASE cannot be used as control class
> -	   when using extended controls.
> -	   Only when passed in through VIDIOC_G_CTRL and VIDIOC_S_CTRL
> -	   is it allowed for backwards compatibility.
> -	 */
> -	if (!allow_priv && c->which == V4L2_CID_PRIVATE_BASE)
> -		return 0;
> -	if (!c->which)
> +	switch (c->which) {
> +	case V4L2_CID_PRIVATE_BASE:
> +		/*
> +		 * V4L2_CID_PRIVATE_BASE cannot be used as control class
> +		 * when using extended controls.
> +		 * Only when passed in through VIDIOC_G_CTRL and VIDIOC_S_CTRL
> +		 * is it allowed for backwards compatibility.
> +		*/
> +		if (!allow_priv)
> +			return 0;
> +		break;
> +	case V4L2_CTRL_WHICH_DEF_VAL:

I think it would be better if a second bool 'is_get' argument is added that is true
for g_ctrl and g_ext_ctrls: then you can do a 'return is_get;' here. That way drivers
do not need to take care of V4L2_CTRL_WHICH_DEF_VAL for set/try.

Regards,

	Hans

> +	case V4L2_CTRL_WHICH_CUR_VAL:
>  		return 1;
> +	case V4L2_CTRL_WHICH_REQUEST_VAL:
> +		return 0;
> +	}
> +
>  	/* Check that all controls are from the same control class. */
>  	for (i = 0; i < c->count; i++) {
>  		if (V4L2_CTRL_ID2WHICH(c->controls[i].id) != c->which) {
>