linux-kernel - Re: [PATCH v3 10/15] media: rcar-csi2: Add .get_frame

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Message-ID: <e529d001-cfac-4f52-a505-0878897e9330@ideasonboard.com>
Date: Tue, 16 Dec 2025 15:22:36 +0200
From: Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>
To: Niklas Söderlund <niklas.soderlund@...natech.se>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>,
 Sakari Ailus <sakari.ailus@...ux.intel.com>, linux-media@...r.kernel.org,
 linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
 Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
 Laurent Pinchart <laurent.pinchart@...asonboard.com>,
 Jacopo Mondi <jacopo.mondi@...asonboard.com>
Subject: Re: [PATCH v3 10/15] media: rcar-csi2: Add .get_frame_desc op

Hi,

On 16/12/2025 15:18, Tomi Valkeinen wrote:
> Hi,
> 
> On 06/06/2025 15:14, Niklas Söderlund wrote:
>> Hi Tomi,
>>
>> Thanks for your work.
>>
>> On 2025-05-30 16:50:39 +0300, Tomi Valkeinen wrote:
>>> Add v4l2_subdev_pad_ops.get_frame_desc() implementation.
>>>
>>> We also implement a fallback for the case where the upstream subdevice
>>> does not implement .get_frame_desc. It assumes a single stream with VC =
>>> 0 and DT based on the configured stream mbus format.
>>>
>>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>
>>> ---
>>>  drivers/media/platform/renesas/rcar-csi2.c | 56 ++++++++++++++++++++++++++++++
>>>  1 file changed, 56 insertions(+)
>>>
>>> diff --git a/drivers/media/platform/renesas/rcar-csi2.c b/drivers/media/platform/renesas/rcar-csi2.c
>>> index 20bd44274bd2..65c7f3040696 100644
>>> --- a/drivers/media/platform/renesas/rcar-csi2.c
>>> +++ b/drivers/media/platform/renesas/rcar-csi2.c
>>> @@ -1676,12 +1676,68 @@ static int rcsi2_set_pad_format(struct v4l2_subdev *sd,
>>>  	return 0;
>>>  }
>>>  
>>> +static int rcsi2_get_frame_desc_fallback(struct v4l2_subdev *sd,
>>> +					 unsigned int pad,
>>> +					 struct v4l2_mbus_frame_desc *fd)
>>> +{
>>> +	const struct rcar_csi2_format *format;
>>> +	struct v4l2_subdev_state *state;
>>> +	struct v4l2_mbus_framefmt *fmt;
>>> +	int ret = 0;
>>> +
>>> +	state = v4l2_subdev_lock_and_get_active_state(sd);
>>> +
>>> +	fmt = v4l2_subdev_state_get_format(state, RCAR_CSI2_SINK, 0);
>>> +	if (!fmt) {
>>> +		ret = -EINVAL;
>>> +		goto out;
>>> +	}
>>> +
>>> +	format = rcsi2_code_to_fmt(fmt->code);
>>> +	if (!format) {
>>> +		ret = -EINVAL;
>>> +		goto out;
>>> +	}
>>> +
>>> +	fd->num_entries = 1;
>>> +	fd->type = V4L2_MBUS_FRAME_DESC_TYPE_CSI2;
>>> +	fd->entry[0].stream = 0;
>>> +	fd->entry[0].pixelcode = fmt->code;
>>> +	fd->entry[0].bus.csi2.vc = 0;
>>> +	fd->entry[0].bus.csi2.dt = format->datatype;
>>> +
>>> +out:
>>> +	v4l2_subdev_unlock_state(state);
>>> +
>>> +	return ret;
>>> +}
>>> +
>>> +static int rcsi2_get_frame_desc(struct v4l2_subdev *sd, unsigned int pad,
>>> +				struct v4l2_mbus_frame_desc *fd)
>>> +{
>>> +	struct rcar_csi2 *priv = sd_to_csi2(sd);
>>> +	int ret;
>>> +
>>> +	if (WARN_ON(!priv->info->use_isp))
>>> +		return -ENOTTY;
>>
>> This looks odd, why can't we support the frame descriptor and streams on 
>> Gen3 that do not use the ISP Channel Selector?
> 
> Yes, this is not right. There was another similar case. I think they are
> remnants of a gen4-only series.

Ah, never mind, now I see. On Gen3 the VINs are connected to the CSI-2.
There's no one that would call get_frame_desc on csi2.

Also, we use v4l2_subdev_get_frame_desc_passthrough() which requires a
1-sink-1-source subdevice, i.e. CSI-2 on Gen4, but not on Gen3.

 Tomi

>>
>>> +
>>> +	if (WARN_ON(pad != RCAR_CSI2_SOURCE_VC0))
>>> +		return -EINVAL;
>>> +
>>> +	ret = v4l2_subdev_get_frame_desc_passthrough(sd, pad, fd);
>>> +	if (ret == -ENOIOCTLCMD)
>>> +		ret = rcsi2_get_frame_desc_fallback(sd, pad, fd);
>>> +	return ret;
>>> +}
>>> +
>>>  static const struct v4l2_subdev_pad_ops rcar_csi2_pad_ops = {
>>>  	.enable_streams = rcsi2_enable_streams,
>>>  	.disable_streams = rcsi2_disable_streams,
>>>  
>>>  	.set_fmt = rcsi2_set_pad_format,
>>>  	.get_fmt = v4l2_subdev_get_fmt,
>>> +
>>> +	.get_frame_desc = rcsi2_get_frame_desc,
>>>  };
>>>  
>>>  static const struct v4l2_subdev_ops rcar_csi2_subdev_ops = {
>>>
>>> -- 
>>> 2.43.0
>>>
>>
>