Re: [PATCH v7 16/34] [media] add Omnivision OV5640 sensor driver

[Sakari Ailus]

On Sat, Jun 03, 2017 at 09:46:36PM -0700, Steve Longerbeam wrote:
> 
> 
> On 06/03/2017 02:57 PM, Sakari Ailus wrote:
> >On Sat, Jun 03, 2017 at 09:51:39PM +0200, Pavel Machek wrote:
> >>Hi!
> >>
> >>>>>>+	/* Auto/manual exposure */
> >>>>>>+	ctrls->auto_exp = v4l2_ctrl_new_std_menu(hdl, ops,
> >>>>>>+						 V4L2_CID_EXPOSURE_AUTO,
> >>>>>>+						 V4L2_EXPOSURE_MANUAL, 0,
> >>>>>>+						 V4L2_EXPOSURE_AUTO);
> >>>>>>+	ctrls->exposure = v4l2_ctrl_new_std(hdl, ops,
> >>>>>>+					    V4L2_CID_EXPOSURE_ABSOLUTE,
> >>>>>>+					    0, 65535, 1, 0);
> >>>>>
> >>>>>Is exposure_absolute supposed to be in microseconds...?
> >>>>
> >>>>Yes.
> >>>
> >>>According to the docs V4L2_CID_EXPOSURE_ABSOLUTE is in 100 usec units.
> >>>
> >>>  OTOH V4L2_CID_EXPOSURE has no defined unit, so it's a better fit IMO.
> >>>>Way more drivers appear to be using EXPOSURE than EXPOSURE_ABSOLUTE, too.
> >>>
> >>>Done, switched to V4L2_CID_EXPOSURE. It's true, this control is not
> >>>taking 100 usec units, so unit-less is better.
> >>
> >>Thanks. If you know the units, it would be of course better to use
> >>right units...
> >
> >Steve: what's the unit in this case? Is it lines or something else?
> 
> Yes, the register interface for exposure takes lines*16.
> 
> Maybe converting from seconds to lines is as simple as
> framerate * height * seconds. But I'm not sure about that.

The smiapp and a few other drivers are using lines. One option could be to
use lines as the unit and have step as 16.

Then the hblank + vblank controls will be needed, too, to enable the user to
at least figure out the conversion to Si units.

-- 
Sakari Ailus
e-mail: sakari.ailus@xxxxxx	XMPP: sailus@xxxxxxxxxxxxxx