Re: [PATCH v3 2/2] media:st-mipid02: MIPID02 CSI-2 to PARALLEL bridge driver

From: Mickael GUENE
Date: Tue Mar 26 2019 - 10:13:32 EST


Sakari,

On 3/26/19 14:54, Sakari Ailus wrote:
> Hi Mickael,
>
> On Tue, Mar 26, 2019 at 12:57:03PM +0000, Mickael GUENE wrote:
> ...
>>>> +static int mipid02_set_fmt(struct v4l2_subdev *sd,
>>>> + struct v4l2_subdev_pad_config *cfg,
>>>> + struct v4l2_subdev_format *format)
>>>> +{
>>>> + struct v4l2_mbus_framefmt *mbus_fmt = &format->format;
>>>> + struct mipid02_dev *bridge = to_mipid02_dev(sd);
>>>> + struct i2c_client *client = bridge->i2c_client;
>>>> + struct v4l2_mbus_framefmt *fmt;
>>>> + int ret;
>>>> +
>>>> + dev_dbg(&client->dev, "%s for %d", __func__, format->pad);
>>>> +
>>>> + if (format->pad >= MIPID02_PAD_NB)
>>>> + return -EINVAL;
>>>> + /* second CSI-2 pad not yet supported */
>>>> + if (format->pad == 1)
>>>> + return -EINVAL;
>>>> +
>>>> + mutex_lock(&bridge->lock);
>>>> +
>>>> + if (bridge->streaming) {
>>>> + ret = -EBUSY;
>>>> + goto error;
>>>> + }
>>>> +
>>>> + if (format->which == V4L2_SUBDEV_FORMAT_TRY)
>>>> + fmt = v4l2_subdev_get_try_format(sd, cfg, format->pad);
>>>> + else
>>>> + fmt = &bridge->fmt;
>>>> +
>>>> + *fmt = *mbus_fmt;
>>>
>>> What are the limits of the hardware regarding the size of the image? Aren't
>>> there any?
>>>
>> There are no limits for image size.
>>> The format on the sink pad needs to be propagated to the source pad as
>>> well. I presume there's nothing to set on the sink pad for this device, is
>>> there?
>> User only need to set format code so the driver can configure hardware.
>> In the mipid02 we have always the same format for sink and source. So I
>> only store one configuration during set_fmt when called from either pad0
>> (sink) or pad2 (source). Is it the correct way to implement it ? or
>> should I only accept set_fmt on pad0 ?
>> For get_fmt I return stored configuration for pad0 and pad2.
>
> Only 76 or so characters per line, please.
>
> For pad 0 (sink) the format must be settable freely (as you don't have any
> hardware restrictions) and on the pad 2 (source) the driver converts the
> format set on the pad 0 according to the hardware functionality. This is
> what the link validation from the source pad onwards is based on.
>
So for a set_fmt on pad 2 I return current configuration ? (as
in my case I have the same configuration for pad 0 and pad2)
And I only update format when set_fmt is called for pad 0 ?

Thanks for your help

Rgs
Mickael