From patchwork Mon Jun 1 06:52:04 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sam Ravnborg X-Patchwork-Id: 11581497 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5CB0B913 for ; Mon, 1 Jun 2020 06:52:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3C4E12077D for ; Mon, 1 Jun 2020 06:52:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="sy/pCIaU" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726860AbgFAGwk (ORCPT ); Mon, 1 Jun 2020 02:52:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44908 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726142AbgFAGwk (ORCPT ); Mon, 1 Jun 2020 02:52:40 -0400 Received: from mail-lj1-x243.google.com (mail-lj1-x243.google.com [IPv6:2a00:1450:4864:20::243]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E31B8C061A0E; Sun, 31 May 2020 23:52:39 -0700 (PDT) Received: by mail-lj1-x243.google.com with SMTP id q2so6724166ljm.10; Sun, 31 May 2020 23:52:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=eLPbrmDW/Xo7kllaN/jCjZjnSWOdy/pm0/gQ/6XVf4A=; b=sy/pCIaUj13T9e3LXdfQwILdRtEsOihqjqCmAlpi+ZAG38uyQTE6UdXc+uASFgFnUp aa0b/ut2gLuNbsSGBSTZi95lJrPlNBQgWJp3VGCmnztKoD/29bqHjc28reTrc9m8ke2t x0wSf/RDekXJuDSRufwrLqpnsuvzvOSziNd7Z/UXDIOVyN4MlnPPwWLvNwvNy971BQGT YoyY9Jd7+mJ2WCIFTd/krWbAxDSrT7PVKvPK8BSy6y672fB/d3bLS9wKC483H4+ZTXwh wAY9ThG1Ar/QQVF/dzX1gNBJo4peBDoXZJ9WwsWsZFBOHSQxhHXc+YiU9DkfR+RHs1c/ LDsA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:from:to:cc:subject:date:message-id :in-reply-to:references:mime-version:content-transfer-encoding; bh=eLPbrmDW/Xo7kllaN/jCjZjnSWOdy/pm0/gQ/6XVf4A=; b=tjiK5BiVwElJ0XJOzooAmxytTG0OrHThvSRmx5U7zfwLdDR507NaMi7FkLJAqIXKFq RZXOs4Mg2ifEmfsqyHKEIqP00xCvFwAoZuAV7QpeaTVWvCIn1O+DC/Iv6qWpluB3N7ma GLryqHVepenwdPC0T2ag+DOCq9bcN2bdiMi1JkbLO+yROIysjxhnFT0DHwkgmrALsent ePfjtsiJdNin01ZNAivZGnYDSCykZdDUp4FxplMtje4ci2OZyidf2dir1ucSEijU8V+m bvxSAZTUONuEnPRHsy1UzsfsKg+jwkyZcrJN/5qDqtCq/+iGiwkwJFzNHIytkwZqeLJC k1DA== X-Gm-Message-State: AOAM530nUG3uWBT9+zS7PBLu/WDYkvF6889a+ozPNsHKVowzCrelnSbn wNXo31nPyKeC3Pbo5BDna0M= X-Google-Smtp-Source: ABdhPJx3iN7XIZ42IHrIlaq3HbS6VzZr9rEiDubQTN25H+BVg8cLbISr3mtT4bLA/BTkd8q1dsTEYg== X-Received: by 2002:a2e:9105:: with SMTP id m5mr10594493ljg.408.1590994358348; Sun, 31 May 2020 23:52:38 -0700 (PDT) Received: from saturn.lan ([2a00:fd00:805f:db00:281d:a604:434c:a58d]) by smtp.gmail.com with ESMTPSA id e13sm2540462ljl.117.2020.05.31.23.52.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 31 May 2020 23:52:37 -0700 (PDT) From: Sam Ravnborg To: dri-devel@lists.freedesktop.org, Jingoo Han , Lee Jones , Daniel Thompson Cc: Andy Gross , Bartlomiej Zolnierkiewicz , Bjorn Andersson , Daniel Vetter , David Airlie , Emil Velikov , Jonathan Corbet , linux-arm-msm@vger.kernel.org, linux-pwm@vger.kernel.org, Maarten Lankhorst , Maxime Ripard , Michael Hennerich , patches@opensource.cirrus.com, Support Opensource , Thierry Reding , Thomas Zimmermann , Uwe Kleine-Konig , Peter Ujfalusi , Tomi Valkeinen , Sam Ravnborg Subject: [PATCH v3 10/13] backlight: add overview and update existing doc Date: Mon, 1 Jun 2020 08:52:04 +0200 Message-Id: <20200601065207.492614-11-sam@ravnborg.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200601065207.492614-1-sam@ravnborg.org> References: <20200601065207.492614-1-sam@ravnborg.org> MIME-Version: 1.0 Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org Add overview chapter to backlight.c. Update existing kernel-doc to follow a more consistent style and drop kernel-doc for deprecated functions. v2: - Sevaral editorial corrections that makes reading much easier (Daniel) - Spelling fixes (Daniel) - updated intro chapter with a little more info Signed-off-by: Sam Ravnborg Cc: Lee Jones Cc: Daniel Thompson Cc: Jingoo Han --- drivers/video/backlight/backlight.c | 131 +++++++++++++++++++--------- 1 file changed, 90 insertions(+), 41 deletions(-) diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c index 17f04cff50ab..06bcddd76a7e 100644 --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -22,6 +22,46 @@ #include #endif +/** + * DOC: overview + * + * The backlight core supports implementing backlight drivers. + * + * A backlight driver registers a driver using + * devm_backlight_device_register(). The properties of the backlight + * driver such as type and max_brightness must be specified. + * When the core detect changes in for example brightness or power state + * the update_status() operation is called. The backlight driver shall + * implement this operation and use it to adjust backlight. + * + * Several sysfs attributes are provided by the backlight core:: + * + * - brightness R/W, set the requested brightness level + * - actual_brighness RO, the brightness level used by the HW + * - max_brightness RO, the maximum brightness level supported + * + * See Documentation/ABI/stable/sysfs-class-backlight for the full list. + * + * The backlight can be adjusted using the sysfs interface, and + * the backlight driver may also support adjusting backlight using + * a hot-key or some other platfrom or firmware specific way. + * + * The driver shall implement the get_brightness() operation if + * the HW do not support all the levels that can be specified in + * brightness, thus providing user-space access to the actual level + * via the actual_brightness attribute. + * When the backlight changes this is reported to user-space using + * an uevent connected to the actual_brightness attribute. + * When brightness is set by platform specific means, for example + * a hot-key to adjust backlight, the driver must notify the backlight + * core that brightness has changed using backlight_force_update(). + * + * The backlight driver core receives notifications from fbdev and + * if the event is FB_EVENT_BLANK and if the value of blank, from the + * FBIOBLANK ioclt, results in a change in the backlight state the + * update_status() operation is called. + */ + static struct list_head backlight_dev_list; static struct mutex backlight_dev_list_mutex; static struct blocking_notifier_head backlight_notifier; @@ -40,9 +80,17 @@ static const char *const backlight_scale_types[] = { #if defined(CONFIG_FB) || (defined(CONFIG_FB_MODULE) && \ defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE)) -/* This callback gets called when something important happens inside a - * framebuffer driver. We're looking if that important event is blanking, - * and if it is and necessary, we're switching backlight power as well ... +/* + * fb_notifier_callback + * + * This callback gets called when something important happens inside a + * framebuffer driver. The backlight core only cares about FB_BLANK_UNBLANK + * which is reported to the driver using backlight_update_status() + * as a state change. + * + * There may be several fbdev's connected to the backlight device, + * in which case they are kept track of. A state change is only reported + * if there is a change in backlight for the specified fbdev. */ static int fb_notifier_callback(struct notifier_block *self, unsigned long event, void *data) @@ -318,12 +366,15 @@ static struct attribute *bl_device_attrs[] = { ATTRIBUTE_GROUPS(bl_device); /** - * backlight_force_update - tell the backlight subsystem that hardware state - * has changed + * backlight_force_update - force an update due to a hardware change * @bd: the backlight device to update + * @reason: the method used for the backlight update * * Updates the internal state of the backlight in response to a hardware event, - * and generate a uevent to notify userspace + * and generates an uevent to notify userspace. A backlight driver shall call + * backlight_force_update() when the backlight is changed using, for example, + * a hot-key. The updated brightness is read using get_brightness() and the + * brightness value is reported using an uevent. */ void backlight_force_update(struct backlight_device *bd, enum backlight_update_reason reason) @@ -336,19 +387,7 @@ void backlight_force_update(struct backlight_device *bd, } EXPORT_SYMBOL(backlight_force_update); -/** - * backlight_device_register - create and register a new object of - * backlight_device class. - * @name: the name of the new object(must be the same as the name of the - * respective framebuffer device). - * @parent: a pointer to the parent device - * @devdata: an optional pointer to be stored for private driver use. The - * methods may retrieve it by using bl_get_data(bd). - * @ops: the backlight operations structure. - * - * Creates and registers new backlight device. Returns either an - * ERR_PTR() or a pointer to the newly allocated device. - */ +/* deprecated - use devm_backlight_device_register() */ struct backlight_device *backlight_device_register(const char *name, struct device *parent, void *devdata, const struct backlight_ops *ops, const struct backlight_properties *props) @@ -415,6 +454,15 @@ struct backlight_device *backlight_device_register(const char *name, } EXPORT_SYMBOL(backlight_device_register); +/** backlight_device_get_by_type - find first backlight device of a type + * @type: the type of backlight device + * + * Look up the first backlight device of the specified type + * + * RETURNS: + * + * Pointer to backlight device if any was found. Otherwise NULL. + */ struct backlight_device *backlight_device_get_by_type(enum backlight_type type) { bool found = false; @@ -433,12 +481,7 @@ struct backlight_device *backlight_device_get_by_type(enum backlight_type type) } EXPORT_SYMBOL(backlight_device_get_by_type); -/** - * backlight_device_unregister - unregisters a backlight device object. - * @bd: the backlight device object to be unregistered and freed. - * - * Unregisters a previously registered via backlight_device_register object. - */ +/* deprecated - use devm_backlight_device_unregister() */ void backlight_device_unregister(struct backlight_device *bd) { if (!bd) @@ -486,10 +529,12 @@ static int devm_backlight_device_match(struct device *dev, void *res, * backlight_register_notifier - get notified of backlight (un)registration * @nb: notifier block with the notifier to call on backlight (un)registration * - * @return 0 on success, otherwise a negative error code - * * Register a notifier to get notified when backlight devices get registered * or unregistered. + * + * RETURNS: + * + * 0 on success, otherwise a negative error code */ int backlight_register_notifier(struct notifier_block *nb) { @@ -501,10 +546,12 @@ EXPORT_SYMBOL(backlight_register_notifier); * backlight_unregister_notifier - unregister a backlight notifier * @nb: notifier block to unregister * - * @return 0 on success, otherwise a negative error code - * * Register a notifier to get notified when backlight devices get registered * or unregistered. + * + * RETURNS: + * + * 0 on success, otherwise a negative error code */ int backlight_unregister_notifier(struct notifier_block *nb) { @@ -513,20 +560,22 @@ int backlight_unregister_notifier(struct notifier_block *nb) EXPORT_SYMBOL(backlight_unregister_notifier); /** - * devm_backlight_device_register - resource managed backlight_device_register() + * devm_backlight_device_register - register a new backlight device * @dev: the device to register * @name: the name of the device - * @parent: a pointer to the parent device + * @parent: a pointer to the parent device (often the same as @dev) * @devdata: an optional pointer to be stored for private driver use * @ops: the backlight operations structure * @props: the backlight properties * - * @return a struct backlight on success, or an ERR_PTR on error + * Creates and registers new backlight device. When a backlight device + * is registered the configuration must be specified in the @props + * parameter. See description of &backlight_properties. * - * Managed backlight_device_register(). The backlight_device returned - * from this function are automatically freed on driver detach. - * See backlight_device_register() for more information. - */ + * RETURNS: + * + * struct backlight on success, or an ERR_PTR on error +*/ struct backlight_device *devm_backlight_device_register(struct device *dev, const char *name, struct device *parent, void *devdata, const struct backlight_ops *ops, @@ -553,13 +602,13 @@ struct backlight_device *devm_backlight_device_register(struct device *dev, EXPORT_SYMBOL(devm_backlight_device_register); /** - * devm_backlight_device_unregister - resource managed backlight_device_unregister() + * devm_backlight_device_unregister - unregister backlight device * @dev: the device to unregister * @bd: the backlight device to unregister * - * Deallocated a backlight allocated with devm_backlight_device_register(). + * Deallocates a backlight allocated with devm_backlight_device_register(). * Normally this function will not need to be called and the resource management - * code will ensure that the resource is freed. + * code will ensure that the resources are freed. */ void devm_backlight_device_unregister(struct device *dev, struct backlight_device *bd) @@ -650,8 +699,8 @@ static void devm_backlight_release(void *data) } /** - * devm_of_find_backlight - Resource-managed of_find_backlight() - * @dev: Device + * devm_of_find_backlight - find backlight for a device + * @dev: the device * * Device managed version of of_find_backlight(). * The reference on the backlight device is automatically