linux-kernel - Re: [PATCH v1 2/3] media:st-mipid02: MIPID02 CSI-2 to PARALLEL bridge driver

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Date:   Tue, 26 Mar 2019 12:07:36 +0000
From:   Mickael GUENE <mickael.guene@...com>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
CC:     Sakari Ailus <sakari.ailus@....fi>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Matt Ranostay <matt.ranostay@...sulko.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ben Kao <ben.kao@...el.com>,
        Todor Tomov <todor.tomov@...aro.org>,
        Rui Miguel Silva <rui.silva@...aro.org>,
        "Akinobu Mita" <akinobu.mita@...il.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        "Jason Chen" <jasonx.z.chen@...el.com>,
        Jacopo Mondi <jacopo+renesas@...ndi.org>,
        Tianshu Qiu <tian.shu.qiu@...el.com>,
        Bingbu Cao <bingbu.cao@...el.com>
Subject: Re: [PATCH v1 2/3] media:st-mipid02: MIPID02 CSI-2 to PARALLEL bridge
 driver

Hello Sakari,

On 3/26/19 12:37, Sakari Ailus wrote:
> On Mon, Mar 25, 2019 at 12:14:05PM +0000, Mickael GUENE wrote:
>> Hi Sakari,
>>
>> On 3/25/19 12:17, Sakari Ailus wrote:
>>> Hi Mickael,
>>>
>>> On Mon, Mar 18, 2019 at 09:57:44AM +0000, Mickael GUENE wrote:
>>>> Hi Sakari,
>>>>
>>>> Thanks for your review. Find my comments below.
>>>>
>>>> On 3/16/19 23:14, Sakari Ailus wrote:
>>> ...
>>>>>> +static struct v4l2_subdev *mipid02_find_sensor(struct mipid02_dev *bridge)
>>>>>> +{
>>>>>> +	struct media_device *mdev = bridge->sd.v4l2_dev->mdev;
>>>>>> +	struct media_entity *entity;
>>>>>> +
>>>>>> +	if (!mdev)
>>>>>> +		return NULL;
>>>>>> +
>>>>>> +	media_device_for_each_entity(entity, mdev)
>>>>>> +		if (entity->function == MEDIA_ENT_F_CAM_SENSOR)
>>>>>> +			return media_entity_to_v4l2_subdev(entity);
>>>>>
>>>>> Hmm. Could you instead use the link state to determine which of the
>>>>> receivers is active? You'll need one more pad, and then you'd had 1:1
>>>>> mapping between ports and pads.
>>>>>
>>>>  Goal here is not to detect which of the receivers is active but to find
>>>> sensor in case there are others sub-dev in chain (for example a 
>>>> serializer/deserializer as found in cars).
>>>
>>> You shouldn't make assumptions on the rest of the pipeline beyond the
>>> device that's directly connected. You might not even have a camera there.
>>>
>>  I have also seen your answer to '[PATCH v2 2/2] media:st-mipid02: MIPID02 CSI-2 to PARALLEL bridge driver'
>> concerning support of set_fmt, get_fmt and link_validate.
>>  My initial idea was to avoid to avoid to implement them and to avoid media ctrl configuration. According
>> to your remark is seems a bad idea. Right ?
> 
> Yes, you'll need them. This is how the media controller pipeline works: a
> driver for a given device is generally only aware of its direct links and
> generally only communicate with drivers for devices directly connected to
> them.
> 
>>  In that case I have to also implement enum_mbus_code ?
> 
> Yes, please.
> 
Ok I will add it in v4
>>  I will drop this code and use connected device only to get link speed.
> 
> Ack.
>