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

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Message-ID: <16e0daf1-1508-462e-8d3c-f5447a803961@ti.com>
Date: Tue, 2 Dec 2025 14:33:46 +0530
From: Rishikesh Donadkar <r-donadkar@...com>
To: Tomi Valkeinen <tomi.valkeinen@...asonboard.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 20/11/25 18:10, Tomi Valkeinen wrote:
>
> 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.


Hi Tomi,

> 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.


Thank you for pointing out, I will change the body of get_frame_desc() 
in this subdev driver set the stream field of the fd to the sink_stream 
of the corresponding route.


Rishikesh

>
> 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 = {