From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrzej Hajda Subject: [RFC 0/2] V4L2 API for exposing flash subdevs as LED class device Date: Mon, 06 May 2013 11:33:46 +0200 Message-ID: <1367832828-30771-1-git-send-email-a.hajda@samsung.com> Return-path: Sender: linux-media-owner@vger.kernel.org To: linux-media@vger.kernel.org, linux-leds@vger.kernel.org, devicetree-discuss@lists.ozlabs.org Cc: Laurent Pinchart , Sylwester Nawrocki , Sakari Ailus , Kyungmin Park , hj210.choi@samsung.com, sw0312.kim@samsung.com, Bryan Wu , Richard Purdie , Andrzej Hajda List-Id: devicetree@vger.kernel.org This RFC proposes generic API for exposing flash subdevices via LED framework. Rationale Currently there are two frameworks which are used for exposing LED flash to user space: - V4L2 flash controls, - LED framework(with custom sysfs attributes). The list below shows flash drivers in mainline kernel with initial commit date and typical chip application (according to producer): LED API: lm3642: 2012-09-12, Cameras lm355x: 2012-09-05, Cameras max8997: 2011-12-14, Cameras (?) lp3944: 2009-06-19, Cameras, Lights, Indicators, Toys pca955x: 2008-07-16, Cameras, Indicators (?) V4L2 API: as3645a: 2011-05-05, Cameras adp1653: 2011-05-05, Cameras V4L2 provides richest functionality, but there is often demand from application developers to provide already established LED API. We would like to have an unified user interface for flash devices. Some of devices already have the LED API driver exposing limited set of a Flash IC functionality. In order to support all required features the LED API would have to be extended or the V4L2 API would need to be used. However when switching from a LED to a V4L2 Flash driver existing LED API interface would need to be retained. Proposed solution This patch adds V4L2 helper functions to register existing V4L2 flash subdev as LED class device. After registration via v4l2_leddev_register appropriate entry in /sys/class/leds/ is created. During registration all V4L2 flash controls are enumerated and corresponding attributes are added. I have attached also patch with new max77693-led driver using v4l2_leddev. This patch requires presence of the patch "max77693: added device tree support": https://patchwork.kernel.org/patch/2414351/ . Additional features - simple API to access all V4L2 flash controls via sysfs, - V4L2 subdevice should not be registered by V4L2 device to use it, - LED triggers API can be used to control the device, - LED device is optional - it will be created only if V4L2_LEDDEV configuration option is enabled and the subdev driver calls v4l2_leddev_register. Doubts This RFC is a result of a uncertainty which API developers should expose by their flash drivers. It is a try to gluing together both APIs. I am not sure if it is the best solution, but I hope there will be some discussion and hopefully some decisions will be taken which way we should follow. Regards Andrzej Hajda Andrzej Hajda (2): v4l2-leddev: added LED class support for V4L2 flash subdevices media: added max77693-led driver drivers/media/i2c/max77693-led.c | 650 +++++++++++++++++++++++++++++++++ drivers/media/v4l2-core/Kconfig | 7 + drivers/media/v4l2-core/Makefile | 1 + drivers/media/v4l2-core/v4l2-leddev.c | 269 ++++++++++++++ include/media/v4l2-leddev.h | 49 +++ 5 files changed, 976 insertions(+) create mode 100644 drivers/media/i2c/max77693-led.c create mode 100644 drivers/media/v4l2-core/v4l2-leddev.c create mode 100644 include/media/v4l2-leddev.h -- 1.7.10.4