linux-kernel - Re: [PATCH v2 10/18] media: cadence: csi2rx: Populate subdev devnode

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Message-ID: <e36baf77-6de8-595d-b440-92bcfcdd8467@ideasonboard.com>
Date:   Fri, 28 May 2021 10:35:11 +0300
From:   Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To:     Pratyush Yadav <p.yadav@...com>
Cc:     Maxime Ripard <mripard@...nel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Vinod Koul <vkoul@...nel.org>,
        Peter Ujfalusi <peter.ujfalusi@...il.com>,
        Steve Longerbeam <slongerbeam@...il.com>,
        Benoit Parrot <bparrot@...com>, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-phy@...ts.infradead.org, dmaengine@...r.kernel.org,
        Vignesh Raghavendra <vigneshr@...com>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Subject: Re: [PATCH v2 10/18] media: cadence: csi2rx: Populate subdev devnode

On 28/05/2021 10:24, Pratyush Yadav wrote:
> On 28/05/21 10:16AM, Tomi Valkeinen wrote:
>> On 26/05/2021 18:23, Pratyush Yadav wrote:
>>> The devnode can be used by media-ctl and other userspace tools to
>>> perform configurations on the subdev. Without it, media-ctl returns
>>> ENOENT when setting format on the sensor subdev.
>>>
>>> Signed-off-by: Pratyush Yadav <p.yadav@...com>
>>> ---
>>>
>>> (no changes since v1)
>>>
>>>    drivers/media/platform/cadence/cdns-csi2rx.c | 1 +
>>>    1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/media/platform/cadence/cdns-csi2rx.c b/drivers/media/platform/cadence/cdns-csi2rx.c
>>> index 1df21f462f3c..49bed63d5faa 100644
>>> --- a/drivers/media/platform/cadence/cdns-csi2rx.c
>>> +++ b/drivers/media/platform/cadence/cdns-csi2rx.c
>>> @@ -613,6 +613,7 @@ static int csi2rx_probe(struct platform_device *pdev)
>>>    	csi2rx->pads[CSI2RX_PAD_SINK].flags = MEDIA_PAD_FL_SINK;
>>>    	for (i = CSI2RX_PAD_SOURCE_STREAM0; i < CSI2RX_PAD_MAX; i++)
>>>    		csi2rx->pads[i].flags = MEDIA_PAD_FL_SOURCE;
>>> +	csi2rx->subdev.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
>>>    	ret = media_entity_pads_init(&csi2rx->subdev.entity, CSI2RX_PAD_MAX,
>>>    				     csi2rx->pads);
>>>
>>
>> I don't understand this one. There's nothing to configure in cdns-csi2rx
>> from userspace, as far as I can see, so why is the dev node needed? And why
>> would the lack of csi2rx dev node cause sensor subdev config to fail?
> 
> Sensor config does not fail. But when I run media-ctl to set the format
> on /dev/media0, I get an error message that comes because the devnode
> for the bridge does not exist. I was not 100% sure about this patch but
> I figured if media-ctl expects it then it should be exposed.
> 
> I don't mind dropping this patch. Just want to make sure what the right
> thing to do here is. Should every element of the pipeline have a devnode
> or not?

Tbh, I don't know. But I don't see why they should have. Also, my test 
works fine if I remove the devnode here.

What media-ctl parameters did you use which fails?

  Tomi