Re: [PATCH v2 3/5] media: mt9p031: Implement [gs]_register debug calls

[Stefan Riedmüller]

Hi Laurent,

On 30.09.20 13:38, Laurent Pinchart wrote:
> Hi Stefan,
>
> Thank you for the patch.
>
> On Wed, Sep 30, 2020 at 12:51:31PM +0200, Stefan Riedmueller wrote:
> > From: Enrico Scholz <enrico.scholz@xxxxxxxxxxxxxxxxx>
> >
> > 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.

Regards,
Stefan

> > Signed-off-by: Enrico Scholz <enrico.scholz@xxxxxxxxxxxxxxxxx>
> > Signed-off-by: Stefan Riedmueller <s.riedmueller@xxxxxxxxx>
> > ---
> > 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 = {