Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751157AbdFDEqn (ORCPT ); Sun, 4 Jun 2017 00:46:43 -0400 Received: from mail-pf0-f196.google.com ([209.85.192.196]:33464 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750812AbdFDEql (ORCPT ); Sun, 4 Jun 2017 00:46:41 -0400 Subject: Re: [PATCH v7 16/34] [media] add Omnivision OV5640 sensor driver To: Sakari Ailus , Pavel Machek Cc: 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 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> From: Steve Longerbeam Message-ID: Date: Sat, 3 Jun 2017 21:46:36 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: <20170603215709.GU1019@valkosipuli.retiisi.org.uk> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1583 Lines: 47 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. Steve > > Pavel: we do need to make sure the user space will be able to know the unit, > 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. > > The exposure is a bit special, too: granularity matters a lot on small > values. On most other controls it does not. >