linux-kernel - Re: [PATCH] media: i2c: imx274: implement enum_mbus

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Message-ID: <f7a04ae1-de4f-2e76-1baa-7bafb970dc10@lucaceresoli.net>
Date:   Thu, 18 Nov 2021 18:39:09 +0100
From:   Luca Ceresoli <luca@...aceresoli.net>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     Eugen Hristev <eugen.hristev@...rochip.com>,
        leonl@...pardimaging.com, linux-media@...r.kernel.org,
        skomatineni@...dia.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: i2c: imx274: implement enum_mbus_code

Hi,

On 18/11/21 18:26, Sakari Ailus wrote:
> Hi Luca,
> 
> On Thu, Nov 18, 2021 at 06:11:35PM +0100, Luca Ceresoli wrote:
>> Hi Eugen,
>>
>> On 18/11/21 16:40, Eugen Hristev wrote:
>>> Current driver supports only SRGGB 10 bit RAW bayer format.
>>> Add the enum_mbus_code implementation to report this format supported.
>>>
>>>  # v4l2-ctl -d /dev/v4l-subdev3 --list-subdev-mbus-codes
>>> ioctl: VIDIOC_SUBDEV_ENUM_MBUS_CODE (pad=0)
>>>         0x300f: MEDIA_BUS_FMT_SRGGB10_1X10
>>>  #
>>>
>>> Signed-off-by: Eugen Hristev <eugen.hristev@...rochip.com>
>>
>> Generally OK, but I have a few minor comments.
>>
>>> ---
>>>  drivers/media/i2c/imx274.c | 14 ++++++++++++++
>>>  1 file changed, 14 insertions(+)
>>>
>>> diff --git a/drivers/media/i2c/imx274.c b/drivers/media/i2c/imx274.c
>>> index 2e804e3b70c4..25a4ef8f6187 100644
>>> --- a/drivers/media/i2c/imx274.c
>>> +++ b/drivers/media/i2c/imx274.c
>>> @@ -1909,7 +1909,21 @@ static int imx274_set_frame_interval(struct stimx274 *priv,
>>>  	return err;
>>>  }
>>>  
>>> +static int imx274_enum_mbus_code(struct v4l2_subdev *sd,
>>> +				 struct v4l2_subdev_state *sd_state,
>>> +				 struct v4l2_subdev_mbus_code_enum *code)
>>> +{
>>> +	if (code->index > 0)
>>> +		return -EINVAL;
>>
>> Many driver do check code->pad too, so you might want to do
>>
>> 	if (code->pad > 0 || code->index > 0)
>> 		return -EINVAL;
> 
> The caller will have checked the pad exists, and there's a single one on
> the subdev I suppose.

Thanks for your explanation. That's very reasonable indeed.

Now, why do many drivers do that? Old checks that later turned useless
and nobody ever removed?

-- 
Luca