linux-kernel - Re: [RFC PATCH 3/3] media: ti: j721e-csi2rx: Add support for VIDIOC_LOG

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Message-ID: <nvyplkcl74rpe7zl2vprfztaivlmwvrsrwyrqw7lbvbeij5ubt@4dehnb7j6ona>
Date: Thu, 13 Feb 2025 18:56:45 +0530
From: Jai Luthra <jai.luthra@...ux.dev>
To: Yemike Abhilash Chandra <y-abhilashchandra@...com>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
	devicetree@...r.kernel.org, mripard@...nel.org, mchehab@...nel.org, robh@...nel.org, 
	krzk+dt@...nel.org, conor+dt@...nel.org, devarsht@...com, vaishnav.a@...com, 
	r-donadkar@...com, u-kumar1@...com
Subject: Re: [RFC PATCH 3/3] media: ti: j721e-csi2rx: Add support for
 VIDIOC_LOG_STATUS

Hi Abhilash,

On Wed, Feb 12, 2025 at 06:42:44PM +0530, Yemike Abhilash Chandra wrote:
> The VIDIOC_LOG_STATUS ioctl outputs the current status of a device to the
> kernel log. When this ioctl is called on a video device, the current
> implementation queries the log status for all connected subdevices in the
> media pipeline.
> 

What is the benefit of doing this for a video node? The user can directly 
check the status on the cdns-csi2rx subdev for CSI errors.

As far as I understand, the video node corresponds to a particular stream, but 
the cdns-csi2rx source pad is shared for all video nodes, so it will report 
the total errors seen for all video nodes in multi-camera scenarios.

This approach will also give you v4l2 control handler status from a few 
sensors (like OV5640) that implement the ioctl using 
v4l2_ctrl_subdev_log_status(), which is probably just noise for the case where 
a user wants to check for stream errors.

> Signed-off-by: Yemike Abhilash Chandra <y-abhilashchandra@...com>
> ---
>  drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
> index 6412a00be8ea..946704458fee 100644
> --- a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
> +++ b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
> @@ -377,6 +377,15 @@ static int ti_csi2rx_enum_framesizes(struct file *file, void *fh,
>  	return 0;
>  }
>  
> +static int ti_csi2rx_log_status(struct file *file, void *fh)
> +{
> +	struct ti_csi2rx_dev *csi = video_drvdata(file);
> +
> +	v4l2_device_call_all(&csi->v4l2_dev, 0, core, log_status);
> +
> +	return 0;
> +}
> +
>  static const struct v4l2_ioctl_ops csi_ioctl_ops = {
>  	.vidioc_querycap      = ti_csi2rx_querycap,
>  	.vidioc_enum_fmt_vid_cap = ti_csi2rx_enum_fmt_vid_cap,
> @@ -393,6 +402,7 @@ static const struct v4l2_ioctl_ops csi_ioctl_ops = {
>  	.vidioc_expbuf        = vb2_ioctl_expbuf,
>  	.vidioc_streamon      = vb2_ioctl_streamon,
>  	.vidioc_streamoff     = vb2_ioctl_streamoff,
> +	.vidioc_log_status	= ti_csi2rx_log_status,
>  };
>  
>  static const struct v4l2_file_operations csi_fops = {
> -- 
> 2.34.1
> 

Thanks,
Jai

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