Hi!

quoted

quoted

+	/* 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. 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.

Ideally we should have only one control for exposure.

No. N-o. No no no. NO! No. N-o. NONONO. No. NooooooooooOOO!!!!!!!!!!!!!

Sorry, no.

Userspace needs to know exposure times. It is not so important for a
webcam, but it is mandatory for digital camera. As it gets darker,
autogain wants to scale exposure to cca 1/100 sec, then it wants to
scale gain up to maximum, and only then it wants to continue scaling
exposure. (Threshold will be shorter in "sports" mode, perhaps
1/300sec?)

Plus, we want user to be able to manually set exposure parameters.

So... _this_ driver probably should use V4L2_CID_EXPOSURE. (If the
units are not known). But in general we'd prefer drivers using
V4L2_CID_EXPOSURE_ABSOLUTE. Your car has speedometer calibrated in
km/h or mph, not in "% of max", right?

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html