Re: [PATCH] v4l2-core: Print control name in VIDIOC_S/G_(EXT)_CTRL(S)

From: Helen Koike <helen.koike@collabora.com>
To: Ezequiel Garcia <ezequiel@collabora.com>, linux-media@vger.kernel.org
Cc: Hans Verkuil <hverkuil@xs4all.nl>, kernel@collabora.com
Subject: Re: [PATCH] v4l2-core: Print control name in VIDIOC_S/G_(EXT)_CTRL(S)
Date: Thu, 11 Jun 2020 09:35:14 -0300	[thread overview]
Message-ID: <c47394e6-4f47-f212-1996-1960663ecfb6@collabora.com> (raw)
In-Reply-To: <20200609121514.9414-1-ezequiel@collabora.com>

On 6/9/20 9:15 AM, Ezequiel Garcia wrote:
> While debugging, it's currently really hard to identify controls
> by their ID. Print the control name making the print more helpful.
> 
> With this change, the print changes from:
> 
> video1: VIDIOC_S_EXT_CTRLS: which=0xf010000, count=5, error_idx=4, request_fd=45, id/size=0x990ce8/1048, id/size=0x990ce9/12, id/size=0x990cea/480, id/size=0x990ceb/896, id/size=0x990cec/400
> 
> to:
> 
> video1: VIDIOC_S_EXT_CTRLS: which=0xf010000, count=5, error_idx=4, request_fd=42, name=H264 Sequence Parameter Set, id/size=0x990ce8/1048, name=H264 Picture Parameter Set, id/size=0x990ce9/12, name=H264 Scaling Matrix, id/size=0x990cea/480, name=H264 Slice Parameters, id/size=0x990ceb/896, name=H264 Decode Parameters, id/size=0x990cec/400
> 
> For instance, this is specially helpful when the ioctl fails. Consider
> the following example:
> 
> v4l2-ctrls: prepare_ext_ctrls: video1: pointer control id 0x990cec size too small, 400 bytes but 784 bytes needed
> v4l2-ctrls: try_set_ext_ctrls: video1: video1: try_set_ext_ctrls_common failed (-14)
> video1: VIDIOC_S_EXT_CTRLS: error -14: which=0xf010000, count=5, error_idx=5, request_fd=39, name=H264 Sequence Parameter Set, id/size=0x990ce8/1048, name=H264 Picture Parameter Set, id/size=0x990ce9/12, name=H264 Scaling Matrix, id/size=0x990cea/480, name=H264 Slice Parameters, id/size=0x990ceb/896, name=H264 Decode Parameters, id/size=0x990cec/400
> 
> Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>

Thanks Ezequiel,

I'll include this in the next RFC.

Regards,
Helen

> ---
>  drivers/media/v4l2-core/v4l2-ioctl.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index 2322f08a98be..4264ac44c48b 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -582,8 +582,10 @@ static void v4l_print_querymenu(const void *arg, bool write_only)
>  static void v4l_print_control(const void *arg, bool write_only)
>  {
>  	const struct v4l2_control *p = arg;
> +	const char *name = v4l2_ctrl_get_name(p->id);
>  
> -	pr_cont("id=0x%x, value=%d\n", p->id, p->value);
> +	pr_cont("name=%s, id=0x%x, value=%d\n",
> +		name ? name : "unknown", p->id, p->value);
>  }
>  
>  static void v4l_print_ext_controls(const void *arg, bool write_only)
> @@ -594,12 +596,16 @@ static void v4l_print_ext_controls(const void *arg, bool write_only)
>  	pr_cont("which=0x%x, count=%d, error_idx=%d, request_fd=%d",
>  			p->which, p->count, p->error_idx, p->request_fd);
>  	for (i = 0; i < p->count; i++) {
> +		unsigned int id = p->controls[i].id;
> +		const char *name = v4l2_ctrl_get_name(id);
> +
> +		name = name ? name : "unknown";
>  		if (!p->controls[i].size)
> -			pr_cont(", id/val=0x%x/0x%x",
> -				p->controls[i].id, p->controls[i].value);
> +			pr_cont(", name=%s, id/val=0x%x/0x%x",
> +				name, id, p->controls[i].value);
>  		else
> -			pr_cont(", id/size=0x%x/%u",
> -				p->controls[i].id, p->controls[i].size);
> +			pr_cont(", name=%s, id/size=0x%x/%u",
> +				name, id, p->controls[i].size);
>  	}
>  	pr_cont("\n");
>  }
> 