linux-kernel - Re: [PATCH v8 10/18] media: cadence: csi2rx: add get_frame

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Message-ID: <ecae251f-3f2e-4f80-8423-09d0e8679416@ideasonboard.com>
Date: Thu, 20 Nov 2025 14:40:29 +0200
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Rishikesh Donadkar <r-donadkar@...com>, jai.luthra@...ux.dev,
 laurent.pinchart@...asonboard.com, mripard@...nel.org
Cc: y-abhilashchandra@...com, devarsht@...com, s-jain1@...com,
 vigneshr@...com, mchehab@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
 p.zabel@...gutronix.de, conor+dt@...nel.org, sakari.ailus@...ux.intel.com,
 hverkuil-cisco@...all.nl, jai.luthra@...asonboard.com,
 changhuang.liang@...rfivetech.com, jack.zhu@...rfivetech.com,
 sjoerd@...labora.com, dan.carpenter@...aro.org, hverkuil+cisco@...nel.org,
 linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
 devicetree@...r.kernel.org
Subject: Re: [PATCH v8 10/18] media: cadence: csi2rx: add get_frame_desc
 wrapper



On 12/11/2025 13:54, Rishikesh Donadkar wrote:
> From: Pratyush Yadav <p.yadav@...com>
> 
> J721E wrapper CSI2RX driver needs to get the frame descriptor from the
> source to find out info about virtual channel. This driver itself does
> not touch the routing or virtual channels in any way. So simply pass the
> descriptor through from the source.

Unfortunately I think that doesn't work.

E.g. we have a fpdllink deser and the cdns csi2rx.

Deser's routing table (pad/stream):

0/0 -> 4/15
0/1 -> 4/33

So we have two streams coming into the deser's pad 0, with stream IDs 0
and 1. They are routed by the user to output pad 4, with stream IDs 15
and 33.

cdns csi2rx routing table:

0/15 -> 1/0
0/33 -> 1/1

So cdns csi2rx routes the streams through, as stream IDs 0 and 1 on the
output side.

With this patch, if the j2 csi2rx asks frame desc from cdns csi2rx, it
gets a frame desc with two streams, stream IDs 15 and 33.

I made this series for the issue above, but it hasn't been merged:

https://lore.kernel.org/all/20250324-frame-desc-passthrough-v4-0-dbe2412297cc%40ideasonboard.com/

 Tomi

> Signed-off-by: Pratyush Yadav <p.yadav@...com>
> Signed-off-by: Jai Luthra <j-luthra@...com>
> Reviewed-by: Jacopo Mondi <jacopo.mondi@...asonboard.com>
> Reviewed-by: Changhuang Liang <changhuang.liang@...rfivetech.com>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Reviewed-by: Yemike Abhilash Chandra <y-abhilashchandra@...com>
> Reviewed-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
> Signed-off-by: Rishikesh Donadkar <r-donadkar@...com>
> ---
>  drivers/media/platform/cadence/cdns-csi2rx.c | 24 ++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/drivers/media/platform/cadence/cdns-csi2rx.c b/drivers/media/platform/cadence/cdns-csi2rx.c
> index 34da81893308b..3688077fa8347 100644
> --- a/drivers/media/platform/cadence/cdns-csi2rx.c
> +++ b/drivers/media/platform/cadence/cdns-csi2rx.c
> @@ -229,6 +229,21 @@ static const struct csi2rx_fmt *csi2rx_get_fmt_by_code(u32 code)
>  	return NULL;
>  }
>  
> +static int csi2rx_get_frame_desc_from_source(struct csi2rx_priv *csi2rx,
> +					     struct v4l2_mbus_frame_desc *fd)
> +{
> +	struct media_pad *remote_pad;
> +
> +	remote_pad = media_entity_remote_source_pad_unique(&csi2rx->subdev.entity);
> +	if (!remote_pad) {
> +		dev_err(csi2rx->dev, "No remote pad found for sink\n");
> +		return -ENODEV;
> +	}
> +
> +	return v4l2_subdev_call(csi2rx->source_subdev, pad, get_frame_desc,
> +				remote_pad->index, fd);
> +}
> +
>  static inline
>  struct csi2rx_priv *v4l2_subdev_to_csi2rx(struct v4l2_subdev *subdev)
>  {
> @@ -611,12 +626,21 @@ int cdns_csi2rx_negotiate_ppc(struct v4l2_subdev *subdev, unsigned int pad,
>  }
>  EXPORT_SYMBOL_FOR_MODULES(cdns_csi2rx_negotiate_ppc, "j721e-csi2rx");
>  
> +static int csi2rx_get_frame_desc(struct v4l2_subdev *subdev, unsigned int pad,
> +				 struct v4l2_mbus_frame_desc *fd)
> +{
> +	struct csi2rx_priv *csi2rx = v4l2_subdev_to_csi2rx(subdev);
> +
> +	return csi2rx_get_frame_desc_from_source(csi2rx, fd);
> +}
> +
>  static const struct v4l2_subdev_pad_ops csi2rx_pad_ops = {
>  	.enum_mbus_code	= csi2rx_enum_mbus_code,
>  	.get_fmt	= v4l2_subdev_get_fmt,
>  	.set_fmt	= csi2rx_set_fmt,
>  	.enable_streams         = csi2rx_enable_streams,
>  	.disable_streams        = csi2rx_disable_streams,
> +	.get_frame_desc	= csi2rx_get_frame_desc,
>  };
>  
>  static const struct v4l2_subdev_core_ops csi2rx_core_ops = {