From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751240AbdFCWRq (ORCPT ); Sat, 3 Jun 2017 18:17:46 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:38214 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751162AbdFCWRo (ORCPT ); Sat, 3 Jun 2017 18:17:44 -0400 Date: Sun, 4 Jun 2017 00:17:41 +0200 From: Pavel Machek To: Sakari Ailus Cc: Steve Longerbeam , robh+dt@kernel.org, mark.rutland@arm.com, shawnguo@kernel.org, kernel@pengutronix.de, fabio.estevam@nxp.com, linux@armlinux.org.uk, mchehab@kernel.org, hverkuil@xs4all.nl, nick@shmanahar.org, markus.heiser@darmarIT.de, p.zabel@pengutronix.de, laurent.pinchart+renesas@ideasonboard.com, bparrot@ti.com, geert@linux-m68k.org, arnd@arndb.de, sudipm.mukherjee@gmail.com, minghsiu.tsai@mediatek.com, tiffany.lin@mediatek.com, jean-christophe.trotin@st.com, horms+renesas@verge.net.au, niklas.soderlund+renesas@ragnatech.se, robert.jarzmik@free.fr, songjun.wu@microchip.com, andrew-ct.chen@mediatek.com, gregkh@linuxfoundation.org, shuah@kernel.org, sakari.ailus@linux.intel.com, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org, devel@driverdev.osuosl.org, Steve Longerbeam Subject: Re: [PATCH v7 16/34] [media] add Omnivision OV5640 sensor driver 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" Content-Disposition: inline In-Reply-To: <20170603215709.GU1019@valkosipuli.retiisi.org.uk> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@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--