From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: [PATCH v7 16/34] [media] add Omnivision OV5640 sensor driver Date: Sun, 4 Jun 2017 00:17:41 +0200 Message-ID: <20170603221741.GA2379@amd> References: <1495672189-29164-1-git-send-email-steve_longerbeam@mentor.com> <1495672189-29164-17-git-send-email-steve_longerbeam@mentor.com> <20170531195821.GA16962@amd> <20170601082659.GJ1019@valkosipuli.retiisi.org.uk> <755909bf-d1de-e0f3-1569-0d4b16e26817@gmail.com> <20170603195139.GA3062@amd> <20170603215709.GU1019@valkosipuli.retiisi.org.uk> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="YiEDa0DAkWCtVeE4" Return-path: Content-Disposition: inline In-Reply-To: <20170603215709.GU1019-S+BSfZ9RZZmRSg0ZkenSGLdO1Tsj/99ntUK59QYPAWc@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Sakari Ailus Cc: Steve Longerbeam , robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, mark.rutland-5wv7dgnIgG8@public.gmane.org, shawnguo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, kernel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org, fabio.estevam-3arQi8VN3Tc@public.gmane.org, linux-I+IVW8TIWO2tmTQ+vhA3Yw@public.gmane.org, mchehab-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, hverkuil-qWit8jRvyhVmR6Xm/wNWPw@public.gmane.org, nick-gcszYUEDH4VrovVCs/uTlw@public.gmane.org, markus.heiser-O6JHGLzbNUwb1SvskN2V4Q@public.gmane.org, p.zabel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org, laurent.pinchart+renesas-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org, bparrot-l0cyMroinI0@public.gmane.org, geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org, arnd-r2nGTMty4D4@public.gmane.org, sudipm.mukherjee-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, minghsiu.tsai-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org, tiffany.lin-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org, jean-christophe.trotin-qxv4g6HH51o@public.gmane.org, horms+renesas-/R6kz+dDXgpPR4JQBCEnsQ@public.gmane.org, niklas.soderlund+renesas-1zkq55x86MTxsAP9Fp7wbw@public.gmane.org, robert.jarzmik-GANU6spQydw@public.gmane.org, songjun.wu-UWL1GkI3JZL3oGB3hsPCZA@public.gmane.org, andrew-ct.chen-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org, gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org, shuah-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, sakari.ailus-VuQAYsv1563Yd54FQh9/CA@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel@l List-Id: devicetree@vger.kernel.org --YiEDa0DAkWCtVeE4 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi! > > > According to the docs V4L2_CID_EXPOSURE_ABSOLUTE is in 100 usec units. > > >=20 > > > 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. > > >=20 > > > Done, switched to V4L2_CID_EXPOSURE. It's true, this control is not > > > taking 100 usec units, so unit-less is better. > >=20 > > Thanks. If you know the units, it would be of course better to use > > right units... >=20 > Steve: what's the unit in this case? Is it lines or something else? >=20 > Pavel: we do need to make sure the user space will be able to know the un= it, > too. It's rather a case with a number of controls: the unit is known but > there's no API to convey it to the user. >=20 > The exposure is a bit special, too: granularity matters a lot on small > values. On most other controls it does not. Yeah. Basically problem with exposure is that the control is logarithmic; by using linear scale we got too much resolution at long times and too little resolution at short times. (Plus, 100 usec ... n900 can do times _way_ shorter than that.) Anyway, even u32 gives us enough range, but I so the linear/log confusion does not matter. But it would be nicer if values were in 10 usec or usec, not 100 usec...=20 Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --YiEDa0DAkWCtVeE4 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlkzNYUACgkQMOfwapXb+vIJtgCgq9LRaStKASXkFpz4aAJY5FVo +8QAnjUE8FZwa10zrYMwuHW9oe3Q58oe =7TFq -----END PGP SIGNATURE----- --YiEDa0DAkWCtVeE4-- -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html