linux-kernel - Re: [PATCH v2 3/5] media: mt9p031: Implement [gs]

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Message-ID: <18667602-f5b6-afa3-0c99-558299c4efb9@phytec.de>
Date:   Mon, 5 Oct 2020 11:33:00 +0200
From:   Stefan Riedmüller <s.riedmueller@...tec.de>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Enrico Scholz <enrico.scholz@...ma-chemnitz.de>
Subject: Re: [PATCH v2 3/5] media: mt9p031: Implement [gs]_register debug
 calls

Hi Laurent,

On 02.10.20 02:06, Laurent Pinchart wrote:
> Hi Stefan,
> 
> On Thu, Oct 01, 2020 at 10:56:24AM +0200, Stefan Riedmüller wrote:
>> On 30.09.20 13:38, Laurent Pinchart wrote:
>>> On Wed, Sep 30, 2020 at 12:51:31PM +0200, Stefan Riedmueller wrote:
>>>> From: Enrico Scholz <enrico.scholz@...ma-chemnitz.de>
>>>>
>>>> Implement g_register and s_register v4l2_subdev_core_ops to access
>>>> camera register directly from userspace for debug purposes.
>>>
>>> As the name of the operations imply, this is meant for debug purpose
>>> only. They are however prone to be abused to configure the sensor from
>>> userspace in production, which isn't a direction we want to take.
>>> What's your use case for this ?  I'd rather drop this patch and see the
>>> driver extended with support for more controls if needed
>>
>> thanks for your feedback.
>>
>> I get your point. I myself solely use these operations for debugging
>> purposes but I'm aware that others like to abuse them.
>>
>> I thought I send it anyway since for me the DEBUG config is enough to
>> signalize that these operations are not to be used with a productive system.
>> But I'm OK with dropping this patch if you think it might send the wrong signal.
> 
> I'd rather avoid this patch due to the risk of abuse if it's OK with
> you.

Yes, that's fine. I will drop it in v3.

Regards,
Stefan

> 
>>>> Signed-off-by: Enrico Scholz <enrico.scholz@...ma-chemnitz.de>
>>>> Signed-off-by: Stefan Riedmueller <s.riedmueller@...tec.de>
>>>> ---
>>>> No changes in v2
>>>> ---
>>>>    drivers/media/i2c/mt9p031.c | 28 ++++++++++++++++++++++++++++
>>>>    1 file changed, 28 insertions(+)
>>>>
>>>> diff --git a/drivers/media/i2c/mt9p031.c b/drivers/media/i2c/mt9p031.c
>>>> index b4c042f418c1..de36025260a8 100644
>>>> --- a/drivers/media/i2c/mt9p031.c
>>>> +++ b/drivers/media/i2c/mt9p031.c
>>>> @@ -703,6 +703,30 @@ static int mt9p031_restore_blc(struct mt9p031 *mt9p031)
>>>>    	return 0;
>>>>    }
>>>>    
>>>> +#ifdef CONFIG_VIDEO_ADV_DEBUG
>>>> +static int mt9p031_g_register(struct v4l2_subdev *sd,
>>>> +			      struct v4l2_dbg_register *reg)
>>>> +{
>>>> +	struct i2c_client *client = v4l2_get_subdevdata(sd);
>>>> +	int ret;
>>>> +
>>>> +	ret = mt9p031_read(client, reg->reg);
>>>> +	if (ret < 0)
>>>> +		return ret;
>>>> +
>>>> +	reg->val = ret;
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +static int mt9p031_s_register(struct v4l2_subdev *sd,
>>>> +			      struct v4l2_dbg_register const *reg)
>>>> +{
>>>> +	struct i2c_client *client = v4l2_get_subdevdata(sd);
>>>> +
>>>> +	return mt9p031_write(client, reg->reg, reg->val);
>>>> +}
>>>> +#endif
>>>> +
>>>>    static int mt9p031_s_ctrl(struct v4l2_ctrl *ctrl)
>>>>    {
>>>>    	struct mt9p031 *mt9p031 =
>>>> @@ -1000,6 +1024,10 @@ static int mt9p031_close(struct v4l2_subdev *subdev, struct v4l2_subdev_fh *fh)
>>>>    
>>>>    static const struct v4l2_subdev_core_ops mt9p031_subdev_core_ops = {
>>>>    	.s_power        = mt9p031_set_power,
>>>> +#ifdef CONFIG_VIDEO_ADV_DEBUG
>>>> +	.s_register	= mt9p031_s_register,
>>>> +	.g_register	= mt9p031_g_register,
>>>> +#endif
>>>>    };
>>>>    
>>>>    static const struct v4l2_subdev_video_ops mt9p031_subdev_video_ops = {
>