From patchwork Tue Jul 9 19:00:04 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthias Kaehlcke X-Patchwork-Id: 11037417 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 166CA912 for ; Tue, 9 Jul 2019 19:00:30 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0859F2870D for ; Tue, 9 Jul 2019 19:00:30 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id F0B1D2872F; Tue, 9 Jul 2019 19:00:29 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8C3D62870D for ; Tue, 9 Jul 2019 19:00:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727250AbfGITAQ (ORCPT ); Tue, 9 Jul 2019 15:00:16 -0400 Received: from mail-pg1-f196.google.com ([209.85.215.196]:35276 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726491AbfGITAO (ORCPT ); Tue, 9 Jul 2019 15:00:14 -0400 Received: by mail-pg1-f196.google.com with SMTP id s27so9926001pgl.2 for ; Tue, 09 Jul 2019 12:00:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=m85WlLZHJVH8RETgsg0HqiVDllfx4XvsXRbdu3drMNc=; b=isQf2VDU03YGOtf8dFbZaoe7mOqoq6z2fbnfI76lyieAkq9c/O3MWRQWJsEu7o6Kv6 +sO3jC2+6lChlABv2PHw4N+6FJo/vPGNbtghULmIYVEdHFqpxVU20P941UYVUnUfnmw0 h+yt4jFHUsAjNf4RH7qkXTZR+LeFbJpXpHuk8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=m85WlLZHJVH8RETgsg0HqiVDllfx4XvsXRbdu3drMNc=; b=Ln98a5x+eP/xi4ffq7mwtdtNLnwkgNIS/QSXFNL1p9+dMA3I8VXjhOAvBjLga3cd1N 004rpn4pgbberMe9uHszIrqTVP+tyOwcf8cJtilREuxn6EcpJpEf13mCaNzY9RogR2cI cNAwIeiBqvSKdtBfQA4T4RnP24nF7tI1KJkviZYTqHsu5jlYrM1Ju5Og7X+ok/gcnbNS +9np1cT/fq67cOZ7IxwyF/KhEPAZGAcSyQrx0pgbqBPMm1KHP6G9T/NixF+0IXAvVoMy nt90L39N3r4FDue2Svv4kkSN+bqH963R+xy1U6ZXYUXT+LE9k26arP7JbZWyZ0PAYDFS K5+Q== X-Gm-Message-State: APjAAAX/lyWglNQZMA3Vkb2LIV2oZ2fhIcdQ5QSqjkXpScDfoU8T0Vhj cDQhDUFv5VyFOtdGIGvQATuFfw== X-Google-Smtp-Source: APXvYqxDiBZW0Xb64K9vuI4D4EUi9LKfdzKQ60nHEzq2OO07kpy0OeqgLete4I10Vsc93WIyQfVezg== X-Received: by 2002:a63:a1a:: with SMTP id 26mr31979652pgk.265.1562698814151; Tue, 09 Jul 2019 12:00:14 -0700 (PDT) Received: from localhost ([2620:15c:202:1:75a:3f6e:21d:9374]) by smtp.gmail.com with ESMTPSA id g62sm3356521pje.11.2019.07.09.12.00.13 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 09 Jul 2019 12:00:13 -0700 (PDT) From: Matthias Kaehlcke To: Thierry Reding , Lee Jones , Daniel Thompson , Jingoo Han , Bartlomiej Zolnierkiewicz Cc: linux-pwm@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, Enric Balletbo i Serra , Douglas Anderson , Brian Norris , Pavel Machek , Jacek Anaszewski , Matthias Kaehlcke Subject: [PATCH v3 1/4] MAINTAINERS: Add entry for stable backlight sysfs ABI documentation Date: Tue, 9 Jul 2019 12:00:04 -0700 Message-Id: <20190709190007.91260-2-mka@chromium.org> X-Mailer: git-send-email 2.22.0.410.gd8fdbe21b5-goog In-Reply-To: <20190709190007.91260-1-mka@chromium.org> References: <20190709190007.91260-1-mka@chromium.org> MIME-Version: 1.0 Sender: linux-fbdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Add an entry for the stable backlight sysfs ABI to the MAINTAINERS file. Signed-off-by: Matthias Kaehlcke Acked-by: Daniel Thompson --- Changes in v3: - none Changes in v2: - added Daniel's 'Acked-by' tag --- MAINTAINERS | 1 + 1 file changed, 1 insertion(+) diff --git a/MAINTAINERS b/MAINTAINERS index 57f496cff999..d51e74340870 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -2857,6 +2857,7 @@ F: drivers/video/backlight/ F: include/linux/backlight.h F: include/linux/pwm_backlight.h F: Documentation/devicetree/bindings/leds/backlight +F: Documentation/ABI/stable/sysfs-class-backlight BATMAN ADVANCED M: Marek Lindner From patchwork Tue Jul 9 19:00:05 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthias Kaehlcke X-Patchwork-Id: 11037405 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 11FA6912 for ; Tue, 9 Jul 2019 19:00:20 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 02C4628726 for ; Tue, 9 Jul 2019 19:00:20 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id EADEF28737; Tue, 9 Jul 2019 19:00:19 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5BB0228726 for ; Tue, 9 Jul 2019 19:00:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727710AbfGITAS (ORCPT ); Tue, 9 Jul 2019 15:00:18 -0400 Received: from mail-pg1-f195.google.com ([209.85.215.195]:42417 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727456AbfGITAQ (ORCPT ); Tue, 9 Jul 2019 15:00:16 -0400 Received: by mail-pg1-f195.google.com with SMTP id t132so9906035pgb.9 for ; Tue, 09 Jul 2019 12:00:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=T12A56st4U6xMjv9tNrkzq8tQL5jOdbBhnZMauX8Bws=; b=SI2rCAS72N9CLesCndW5GOG2uj6BrMPw1IuIl2eGt1duNnrycvb0HSTo7g2HFa1dw6 jre8ouKqMScn+GMJN2aW8u5WpdLg/vvwtRO68eGyrvh+hIhbuIR2XNab2JOlmMjR9svO NzG03XiTXHzv8UWz60/01C2e7bjXzIlH5mj70= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=T12A56st4U6xMjv9tNrkzq8tQL5jOdbBhnZMauX8Bws=; b=DVvp3ZbclbM7gJsLb7YQu3sBqihNqWeS6afK7UMxgK9u6Y+elDqxYJhxUWDcNP5Ysz cfTQPl7QxCDy/DwyDUn1WDUmpXMhfG6zXIRfPFCl6xngXnGeP9h1+JFwJI4OgvmkAVyr n7ay29Yf6iJc6KzkoOgbZuhrM2zP2yGj9EDwubrQRRKIsJN2FGhcxe4VcXSEN3QbFoLV 7bwV3bnfiKP5hIipmYlcSg8pvR5ufSfCxYS6iSBEIi/WpnicfXZtwj7pAVSFU3XhRWhq SjR/dGAn/fQrSr+J4ozXTy3y1oPj8ii3ImavreFk4kzJuRAHE+XOYsjDr+brcxU/4ijX hZNw== X-Gm-Message-State: APjAAAXxcYNwhkJ+CxRsBxQEJv+ojMe38RgaVbCK2/EXq3pbz9x/W211 u0gUkHvL4QDB7CXFzj/o/9jk5g== X-Google-Smtp-Source: APXvYqyEa4ryD7UuELRziTCBGlJ9o4biH2jBafr0m0ioDSkfIt9v3ZzlZ12RUj4fyPMeD5pAkrk6Hw== X-Received: by 2002:a63:7519:: with SMTP id q25mr439220pgc.13.1562698815766; Tue, 09 Jul 2019 12:00:15 -0700 (PDT) Received: from localhost ([2620:15c:202:1:75a:3f6e:21d:9374]) by smtp.gmail.com with ESMTPSA id b15sm20363265pfi.141.2019.07.09.12.00.14 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 09 Jul 2019 12:00:15 -0700 (PDT) From: Matthias Kaehlcke To: Thierry Reding , Lee Jones , Daniel Thompson , Jingoo Han , Bartlomiej Zolnierkiewicz Cc: linux-pwm@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, Enric Balletbo i Serra , Douglas Anderson , Brian Norris , Pavel Machek , Jacek Anaszewski , Matthias Kaehlcke Subject: [PATCH v3 2/4] backlight: Expose brightness curve type through sysfs Date: Tue, 9 Jul 2019 12:00:05 -0700 Message-Id: <20190709190007.91260-3-mka@chromium.org> X-Mailer: git-send-email 2.22.0.410.gd8fdbe21b5-goog In-Reply-To: <20190709190007.91260-1-mka@chromium.org> References: <20190709190007.91260-1-mka@chromium.org> MIME-Version: 1.0 Sender: linux-fbdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Backlight brightness curves can have different shapes. The two main types are linear and non-linear curves. The human eye doesn't perceive linearly increasing/decreasing brightness as linear (see also 88ba95bedb79 "backlight: pwm_bl: Compute brightness of LED linearly to human eye"), hence many backlights use non-linear (often logarithmic) brightness curves. The type of curve currently is opaque to userspace, so userspace often uses more or less reliable heuristics (like the number of brightness levels) to decide whether to treat a backlight device as linear or non-linear. Export the type of the brightness curve via the new sysfs attribute 'scale'. The value of the attribute can be 'linear', 'non-linear' or 'unknown'. For devices that don't provide information about the scale of their brightness curve the value of the 'scale' attribute is 'unknown'. Signed-off-by: Matthias Kaehlcke Reviewed-by: Daniel Thompson --- Feel free to suggest improvements in the documentation :) Changes in v3: - removed composite strings, only keep 'linear', 'non-linear' and 'unknown' - updated sysfs attribute documentation - updated commit message Changes in v2: - changed order of brightness scale enums, explicitly make 'unknown' zero - minor update of commit message - deleted excess blank line after 'backlight_scale_types' - s/curves/curve/ in sysfs doc --- .../ABI/testing/sysfs-class-backlight | 26 +++++++++++++++++++ MAINTAINERS | 1 + drivers/video/backlight/backlight.c | 19 ++++++++++++++ include/linux/backlight.h | 8 ++++++ 4 files changed, 54 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-class-backlight diff --git a/Documentation/ABI/testing/sysfs-class-backlight b/Documentation/ABI/testing/sysfs-class-backlight new file mode 100644 index 000000000000..3ab175a3f5cb --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-backlight @@ -0,0 +1,26 @@ +What: /sys/class/backlight//scale +Date: July 2019 +KernelVersion: 5.4 +Contact: Daniel Thompson +Description: + Description of the scale of the brightness curve. + + The human eye senses brightness approximately logarithmically, + hence linear changes in brightness are perceived as being + non-linear. To achieve a linear perception of brightness changes + controls like sliders need to apply a logarithmic mapping for + backlights with a linear brightness curve. + + Possible values of the attribute are: + + unknown + The scale of the brightness curve is unknown. + + linear + The brightness changes linearly with each step. Brightness + controls should apply a logarithmic mapping for a linear + perception. + + non-linear + The brightness changes non-linearly with each step. Brightness + controls should use a linear mapping for a linear perception. diff --git a/MAINTAINERS b/MAINTAINERS index d51e74340870..c46812510ba5 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -2858,6 +2858,7 @@ F: include/linux/backlight.h F: include/linux/pwm_backlight.h F: Documentation/devicetree/bindings/leds/backlight F: Documentation/ABI/stable/sysfs-class-backlight +F: Documentation/ABI/testing/sysfs-class-backlight BATMAN ADVANCED M: Marek Lindner diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c index 1ef8b6fd62ac..277abc76c83a 100644 --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -32,6 +32,12 @@ static const char *const backlight_types[] = { [BACKLIGHT_FIRMWARE] = "firmware", }; +static const char *const backlight_scale_types[] = { + [BACKLIGHT_SCALE_UNKNOWN] = "unknown", + [BACKLIGHT_SCALE_LINEAR] = "linear", + [BACKLIGHT_SCALE_NON_LINEAR] = "non-linear", +}; + #if defined(CONFIG_FB) || (defined(CONFIG_FB_MODULE) && \ defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE)) /* This callback gets called when something important happens inside a @@ -246,6 +252,18 @@ static ssize_t actual_brightness_show(struct device *dev, } static DEVICE_ATTR_RO(actual_brightness); +static ssize_t scale_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct backlight_device *bd = to_backlight_device(dev); + + if (WARN_ON(bd->props.scale > BACKLIGHT_SCALE_NON_LINEAR)) + return sprintf(buf, "unknown\n"); + + return sprintf(buf, "%s\n", backlight_scale_types[bd->props.scale]); +} +static DEVICE_ATTR_RO(scale); + static struct class *backlight_class; #ifdef CONFIG_PM_SLEEP @@ -292,6 +310,7 @@ static struct attribute *bl_device_attrs[] = { &dev_attr_brightness.attr, &dev_attr_actual_brightness.attr, &dev_attr_max_brightness.attr, + &dev_attr_scale.attr, &dev_attr_type.attr, NULL, }; diff --git a/include/linux/backlight.h b/include/linux/backlight.h index 0b5897446dca..c7d6b2e8c3b5 100644 --- a/include/linux/backlight.h +++ b/include/linux/backlight.h @@ -46,6 +46,12 @@ enum backlight_notification { BACKLIGHT_UNREGISTERED, }; +enum backlight_scale { + BACKLIGHT_SCALE_UNKNOWN = 0, + BACKLIGHT_SCALE_LINEAR, + BACKLIGHT_SCALE_NON_LINEAR, +}; + struct backlight_device; struct fb_info; @@ -80,6 +86,8 @@ struct backlight_properties { enum backlight_type type; /* Flags used to signal drivers of state changes */ unsigned int state; + /* Type of the brightness scale (linear, non-linear, ...) */ + enum backlight_scale scale; #define BL_CORE_SUSPENDED (1 << 0) /* backlight is suspended */ #define BL_CORE_FBBLANK (1 << 1) /* backlight is under an fb blank event */ From patchwork Tue Jul 9 19:00:06 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthias Kaehlcke X-Patchwork-Id: 11037415 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 2A3CE13A4 for ; Tue, 9 Jul 2019 19:00:28 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1A67B2870D for ; Tue, 9 Jul 2019 19:00:28 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 0EDBD2872F; 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Tue, 09 Jul 2019 12:00:17 -0700 (PDT) Received: from localhost ([2620:15c:202:1:75a:3f6e:21d:9374]) by smtp.gmail.com with ESMTPSA id o14sm2998437pjp.19.2019.07.09.12.00.16 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 09 Jul 2019 12:00:16 -0700 (PDT) From: Matthias Kaehlcke To: Thierry Reding , Lee Jones , Daniel Thompson , Jingoo Han , Bartlomiej Zolnierkiewicz Cc: linux-pwm@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, Enric Balletbo i Serra , Douglas Anderson , Brian Norris , Pavel Machek , Jacek Anaszewski , Matthias Kaehlcke Subject: [PATCH v3 3/4] backlight: pwm_bl: Set scale type for CIE 1931 curves Date: Tue, 9 Jul 2019 12:00:06 -0700 Message-Id: <20190709190007.91260-4-mka@chromium.org> X-Mailer: git-send-email 2.22.0.410.gd8fdbe21b5-goog In-Reply-To: <20190709190007.91260-1-mka@chromium.org> References: <20190709190007.91260-1-mka@chromium.org> MIME-Version: 1.0 Sender: linux-fbdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP For backlight curves calculated with the CIE 1931 algorithm set the brightness scale type to non-linear. This makes the scale type available to userspace via the 'scale' sysfs attribute. Signed-off-by: Matthias Kaehlcke Tested-by: Enric Balletbo i Serra Acked-by: Daniel Thompson --- Changes in v3: - mark scale as non-linear instead of using the CIE1931 type which has been removed - updated commit message Changes in v2: - added Enric's 'Tested-by' tag - added Daniel's 'Acked-by' tag --- drivers/video/backlight/pwm_bl.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index fb45f866b923..7c6dfc4a601d 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -553,6 +553,8 @@ static int pwm_backlight_probe(struct platform_device *pdev) goto err_alloc; } + memset(&props, 0, sizeof(struct backlight_properties)); + if (data->levels) { /* * For the DT case, only when brightness levels is defined @@ -591,6 +593,8 @@ static int pwm_backlight_probe(struct platform_device *pdev) pb->levels = data->levels; } + + props.scale = BACKLIGHT_SCALE_NON_LINEAR; } else { /* * That only happens for the non-DT case, where platform data @@ -601,7 +605,6 @@ static int pwm_backlight_probe(struct platform_device *pdev) pb->lth_brightness = data->lth_brightness * (state.period / pb->scale); - memset(&props, 0, sizeof(struct backlight_properties)); props.type = BACKLIGHT_RAW; props.max_brightness = data->max_brightness; bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb, From patchwork Tue Jul 9 19:00:07 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthias Kaehlcke X-Patchwork-Id: 11037413 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 05AAF912 for ; Tue, 9 Jul 2019 19:00:26 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id EB6412870D for ; Tue, 9 Jul 2019 19:00:25 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id DFD9C2872F; Tue, 9 Jul 2019 19:00:25 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 808A12870D for ; 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This makes the scale type available to userspace via the 'scale' sysfs attribute. To determine if a curve is linear it is compared to a interpolated linear curve between min and max brightness. The curve is considered linear if no value deviates more than +/-5% of ${brightness_range} from their interpolated value. Signed-off-by: Matthias Kaehlcke Acked-by: Daniel Thompson --- Changes in v3: - none Changes in v2: - use 128 (power of two) instead of 100 as factor for the slope - add comment about max quantization error - added Daniel's 'Acked-by' tag --- drivers/video/backlight/pwm_bl.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index 7c6dfc4a601d..fef98beb8b7e 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -404,6 +404,31 @@ int pwm_backlight_brightness_default(struct device *dev, } #endif +static bool pwm_backlight_is_linear(struct platform_pwm_backlight_data *data) +{ + unsigned int nlevels = data->max_brightness + 1; + unsigned int min_val = data->levels[0]; + unsigned int max_val = data->levels[nlevels - 1]; + /* + * Multiplying by 128 means that even in pathological cases such + * as (max_val - min_val) == nlevels the error at max_val is less + * than 1%. + */ + unsigned int slope = (128 * (max_val - min_val)) / nlevels; + unsigned int margin = (max_val - min_val) / 20; /* 5% */ + int i; + + for (i = 1; i < nlevels; i++) { + unsigned int linear_value = min_val + ((i * slope) / 128); + unsigned int delta = abs(linear_value - data->levels[i]); + + if (delta > margin) + return false; + } + + return true; +} + static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb) { struct device_node *node = pb->dev->of_node; @@ -567,6 +592,11 @@ static int pwm_backlight_probe(struct platform_device *pdev) pb->levels = data->levels; } + + if (pwm_backlight_is_linear(data)) + props.scale = BACKLIGHT_SCALE_LINEAR; + else + props.scale = BACKLIGHT_SCALE_NON_LINEAR; } else if (!data->max_brightness) { /* * If no brightness levels are provided and max_brightness is