From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f54.google.com (mail-wm1-f54.google.com [209.85.128.54]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3A7A53A7F69 for ; Tue, 20 Jan 2026 09:38:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.54 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768901928; cv=none; b=GTLew8bZ/fRwilNq60B1R0r2oBvaUVvojbpq4la0B56dhKaAitnUOHVuobX+DfE+4L3Tx325au2LJvbNHV9ILA5xXDw812NIdxarc5eeeHizXPgGszarG4rMy2g0qnS+CaayvxSyOtNnoLiigCpXDuKTxhmg8U0IyvptyCuDEXY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768901928; c=relaxed/simple; bh=fe4X9cUXePaawaT4qNrxQlN770EBdOFRImJxWrnEhUM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=QhS6w4du7J+Ee+iHFl6Um696R7/pKw8fcQEc15JhU6aDqcwscojfbZzgY3DHUju3OWSvwtbHv9F5/voPD3DFv5o2+1o13GErBLD63FJTD85d2csJz+7eBxi4mGQltlRvDJ2AWfS7eaJQbnsex6tStAE5KGzRtonb5I9+WX6QGlA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=riscstar.com; spf=pass smtp.mailfrom=riscstar.com; dkim=pass (2048-bit key) header.d=riscstar-com.20230601.gappssmtp.com header.i=@riscstar-com.20230601.gappssmtp.com header.b=GhRrHXHH; arc=none smtp.client-ip=209.85.128.54 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=riscstar.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=riscstar.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=riscstar-com.20230601.gappssmtp.com header.i=@riscstar-com.20230601.gappssmtp.com header.b="GhRrHXHH" Received: by mail-wm1-f54.google.com with SMTP id 5b1f17b1804b1-47edffe5540so44484605e9.0 for ; Tue, 20 Jan 2026 01:38:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=riscstar-com.20230601.gappssmtp.com; s=20230601; t=1768901922; x=1769506722; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=JPcPIZUGx04qHWK759PItSENS0mcgGK/1dry0pxcZSU=; b=GhRrHXHHA9XaNb+N7dT+VVb9laC5CpSkVTTKe+PupT/lRLgQ83mBZXWKCkmhAyi2UY CVCzzN67E8BjO7b6BiUpNDt9VF2SlDZlRjP29WGrb83debl1URarYxs1KzgmggvUOlnx 8B6dHxQaV2NvYHurlqmcxVTujXImSXzUUoFFVIXzFE4zENdEKN/D0N4+tQ+jPyWtChp1 4yb6XglKY4WsOcsujYTZXpK24Abwi37HLyLDVodkjtuzKGf//4fnEbsnuwW0uHW3K910 KZ0sxV3yX5yJBUewQhBrB9njahWB7LEHtHVuv3s12+axHmCIxTK7EMcp6/cRS/j80r4A 4r9A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1768901922; x=1769506722; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=JPcPIZUGx04qHWK759PItSENS0mcgGK/1dry0pxcZSU=; b=WDZK+RwApxZk7UhBJj99E47aQ6NqSHHJPU7q6rsWRyoIDD0POlSvRgDxSwlgtBh/Vm aH7K8JzaUInJxlV6ksuQa9CCcSMjm2HKlEd8CUimLaucqXgkABKt3f/1FwxSHgNUgZ5p GAd6CP3NmueJH5TWfJgMUmRQg4PoT3Ox5JapMbslEnnws8GQRbu2TQVIflwp/c0CEArL Uzla3Cm729n5itocHtOM099Ot8URqwtmQors6T9IIOMo7B+SPCvbFN1CERTMyXa8q9kN TFwkxEeTLhB2g0f9cS1dqcqt16nG+kkNNneYn+q01L/Z+xLiYrIDkZkPZzFsGre4ROe3 GoBQ== X-Forwarded-Encrypted: i=1; AJvYcCVNj2Wp2cHMwQnR/oa7tMOW+0BtTnhDtlLwtX1UE9gMePfDg+1D99s44fBghEmrG9iFiwjTwqkTFi8M@vger.kernel.org X-Gm-Message-State: AOJu0YyyxO8IrZhiaeut+AuBBoo6qe6u4ge8bvKtePAZxZtUfdOzOdOD hex17ACHIrGWJEQHPlGqq8ofRAbw8aOvLkDLTCuBO738fUDNx5Gva9AKJIlmREjCWvE= X-Gm-Gg: AY/fxX4LKLaaePA1KlU8OQc91uMeNdEVO52kifnc320NDecmHKsNZ05nY4sAwAQyU43 nd3q/oRZBfZWhq97fApKJhx9buwcA+LG2eatdOkJk/XOyaAR6Xe+GNSpWe4eNLqTE8jn1pMF+jH GnBf40DYT66mkpTltB36HpcOdujnpF1GlASxhpmYpEeMqp6gUf5Bd0hzj8TmQzhsVfbvnMb3PFZ 5XBpxN24i4uiDVKmLKwxX5VFA1ShPurzUyawnbxSPxXLMttEffENvr04M7/7ybgYbs/buCsqn2B 0CR+1GzGTX4KX2MSgxqhkx9KSPEvNK50vO+t4eyhQ8ENAkmGuWOB0/BwNjAN+oCg2rPmbOiIAcw IEmbY/6kqiS2xfe5CT2qqptI5zaDEpejRjW2ac91xQ4qGiyu+Xqk0dNLuFSk7EaY9+Sc6iT8fUk yJ58c1PkPQK1Llas1nxx1GV2LPScQyVMvvu6yCVGlKUXx5Eg3/MsxC6ITgv9yc0Ov2Tb7kSbWlt 18NF+rfcspaJW1i9rqi/Cc7i6imS+CxC10w0z45Xif8YZUUGKMBLF0CRazgCuIVkLZsRRSO X-Received: by 2002:a05:600c:1d14:b0:47d:4fbe:e6cc with SMTP id 5b1f17b1804b1-4803e7a39damr16391835e9.13.1768901922024; Tue, 20 Jan 2026 01:38:42 -0800 (PST) Received: from aspen.lan (aztw-34-b2-v4wan-166919-cust780.vm26.cable.virginm.net. [82.37.195.13]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47f4b267661sm298932175e9.13.2026.01.20.01.38.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Jan 2026 01:38:41 -0800 (PST) Date: Tue, 20 Jan 2026 09:38:39 +0000 From: Daniel Thompson To: tessolveupstream@gmail.com Cc: lee@kernel.org, danielt@kernel.org, jingoohan1@gmail.com, deller@gmx.de, pavel@kernel.org, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-leds@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v1 2/2] backlight: gpio: add support for multiple GPIOs for backlight control Message-ID: References: <20260105085120.230862-1-tessolveupstream@gmail.com> <20260105085120.230862-3-tessolveupstream@gmail.com> <1fedb7d7-3a30-4f0f-961f-09613f2a95d0@gmail.com> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Jan 20, 2026 at 10:22:02AM +0530, tessolveupstream@gmail.com wrote: > > > On 14-01-2026 21:33, Daniel Thompson wrote: > > On Tue, Jan 13, 2026 at 12:47:26PM +0530, tessolveupstream@gmail.com wrote: > >> > >> > >> On 05-01-2026 15:39, Daniel Thompson wrote: > >>> On Mon, Jan 05, 2026 at 02:21:20PM +0530, Sudarshan Shetty wrote: > >>>> Extend the gpio-backlight driver to handle multiple GPIOs instead of a > >>>> single one. This allows panels that require driving several enable pins > >>>> to be controlled by the backlight framework. > >>>> > >>>> Signed-off-by: Sudarshan Shetty > >>>> --- > >>>> drivers/video/backlight/gpio_backlight.c | 61 +++++++++++++++++------- > >>>> 1 file changed, 45 insertions(+), 16 deletions(-) > >>>> > >>>> diff --git a/drivers/video/backlight/gpio_backlight.c b/drivers/video/backlight/gpio_backlight.c > >>>> index 728a546904b0..037e1c111e48 100644 > >>>> --- a/drivers/video/backlight/gpio_backlight.c > >>>> +++ b/drivers/video/backlight/gpio_backlight.c > >>>> @@ -17,14 +17,18 @@ > >>>> > >>>> struct gpio_backlight { > >>>> struct device *dev; > >>>> - struct gpio_desc *gpiod; > >>>> + struct gpio_desc **gpiods; > >>>> + unsigned int num_gpios; > >>> > >>> Why not use struct gpio_descs for this? > >>> > >>> Once you do that, then most of the gbl->num_gpios loops can be replaced with > >>> calls to the array based accessors. > >>> > >> > >> Based on your feedback, I have updated the implementation to use > >> struct gpio_descs and array-based accessors, as recommended like > >> below: > >> > >> git diff drivers/video/backlight/gpio_backlight.c > >> diff --git a/drivers/video/backlight/gpio_backlight.c b/drivers/video/backlight/gpio_backlight.c > >> index 037e1c111e48..e99d7a9dc670 100644 > >> --- a/drivers/video/backlight/gpio_backlight.c > >> +++ b/drivers/video/backlight/gpio_backlight.c > >> @@ -14,22 +14,37 @@ > >> #include > >> #include > >> #include > >> +#include > >> > >> struct gpio_backlight { > >> struct device *dev; > >> - struct gpio_desc **gpiods; > >> + struct gpio_descs *gpiods; > >> unsigned int num_gpios; > >> }; > >> > >> static int gpio_backlight_update_status(struct backlight_device *bl) > >> { > >> struct gpio_backlight *gbl = bl_get_data(bl); > >> - unsigned int i; > >> + unsigned int n = gbl->num_gpios; > >> int br = backlight_get_brightness(bl); > >> + unsigned long *value_bitmap; > >> + int words = BITS_TO_LONGS(n); > >> + > >> + value_bitmap = kcalloc(words, sizeof(unsigned long), GFP_KERNEL); > > > > Not sure you need a kcalloc() here. If you want to support more than 32 > > GPIOs then you can pre-allocate space with a devm_kcalloc() in the probe > > method rather than reallocate every time it is used. > > > > To be honest I don't really mind putting a hard limit on the maximum > > gpl->num_gpios (so you can just use a local variable) and having no > > allocation at all. > > > > Thanks for the suggestion. I addressed the kcalloc() concern by > moving the bitmap allocation to probe using devm_kcalloc() as > below: > > diff --git a/drivers/video/backlight/gpio_backlight.c b/drivers/video/backlight/gpio_backlight.c > index 0eb42d8bf1d9..7af5dc4f0315 100644 > --- a/drivers/video/backlight/gpio_backlight.c > +++ b/drivers/video/backlight/gpio_backlight.c > @@ -19,32 +19,25 @@ > struct gpio_backlight { > struct device *dev; > struct gpio_descs *gpiods; > - unsigned int num_gpios; > + unsigned long *bitmap; > }; > > static int gpio_backlight_update_status(struct backlight_device *bl) > { > struct gpio_backlight *gbl = bl_get_data(bl); > - unsigned int n = gbl->num_gpios; > + unsigned int n = gbl->gpiods->ndescs; > int br = backlight_get_brightness(bl); > - unsigned long *value_bitmap; > - int words = BITS_TO_LONGS(n); > - > - value_bitmap = kcalloc(words, sizeof(unsigned long), GFP_KERNEL); > - if (!value_bitmap) > - return -ENOMEM; > > if (br) > - bitmap_fill(value_bitmap, n); > + bitmap_fill(gbl->bitmap, n); > else > - bitmap_zero(value_bitmap, n); > + bitmap_zero(gbl->bitmap, n); > > - gpiod_set_array_value_cansleep(gbl->gpiods->ndescs, > + gpiod_set_array_value_cansleep(n, > gbl->gpiods->desc, > gbl->gpiods->info, > - value_bitmap); > + gbl->bitmap); > > - kfree(value_bitmap); > return 0; > } > > @@ -67,22 +60,25 @@ static int gpio_backlight_probe(struct platform_device *pdev) > struct device *dev = &pdev->dev; > struct gpio_backlight_platform_data *pdata = dev_get_platdata(dev); > struct device_node *of_node = dev->of_node; > - struct backlight_properties props; > + struct backlight_properties props = { }; > struct backlight_device *bl; > struct gpio_backlight *gbl; > - int ret, init_brightness, def_value; > - unsigned int i; > + bool def_value; > + enum gpiod_flags flags; > + unsigned int n; > + int words; > > - gbl = devm_kzalloc(dev, sizeof(*gbl), GFP_KERNEL); > - if (gbl == NULL) > + gbl = devm_kcalloc(dev, 1, sizeof(*gbl), GFP_KERNEL); > + if (!gbl) > return -ENOMEM; > > if (pdata) > gbl->dev = pdata->dev; > > def_value = device_property_read_bool(dev, "default-on"); > - > - gbl->gpiods = devm_gpiod_get_array(dev, NULL, GPIOD_ASIS); > + flags = def_value ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW; > + > + gbl->gpiods = devm_gpiod_get_array(dev, NULL, flags); > if (IS_ERR(gbl->gpiods)) { > if (PTR_ERR(gbl->gpiods) == -ENODEV) > return dev_err_probe(dev, -EINVAL, > @@ -90,12 +86,17 @@ static int gpio_backlight_probe(struct platform_device *pdev) > return PTR_ERR(gbl->gpiods); > } > > - gbl->num_gpios = gbl->gpiods->ndescs; > - if (gbl->num_gpios == 0) > + n = gbl->gpiods->ndescs; > + if (!n) > return dev_err_probe(dev, -EINVAL, > - "The gpios parameter is missing or invalid\n"); > + "No GPIOs provided\n"); > + > + words = BITS_TO_LONGS(n); > + gbl->bitmap = devm_kcalloc(dev, words, sizeof(unsigned long), > + GFP_KERNEL); > + if (!gbl->bitmap) > + return -ENOMEM; > > - memset(&props, 0, sizeof(props)); > props.type = BACKLIGHT_RAW; > props.max_brightness = 1; > bl = devm_backlight_device_register(dev, dev_name(dev), dev, gbl, > @@ -106,50 +107,19 @@ static int gpio_backlight_probe(struct platform_device *pdev) > } > > /* Set the initial power state */ > - if (!of_node || !of_node->phandle) { > + if (!of_node || !of_node->phandle) > /* Not booted with device tree or no phandle link to the node */ > bl->props.power = def_value ? BACKLIGHT_POWER_ON > : BACKLIGHT_POWER_OFF; > - } else { > - bool all_high = true; > - unsigned long *value_bitmap; > - int words = BITS_TO_LONGS(gbl->num_gpios); > - > - value_bitmap = kcalloc(words, sizeof(unsigned long), > - GFP_KERNEL); > - if (!value_bitmap) > - return -ENOMEM; > - > - ret = gpiod_get_array_value_cansleep(gbl->gpiods->ndescs, > - gbl->gpiods->desc, > - gbl->gpiods->info, > - value_bitmap); > - if (ret) { > - kfree(value_bitmap); > - return dev_err_probe(dev, ret, > - "failed to read initial gpio values\n"); > - } > - > - all_high = bitmap_full(value_bitmap, gbl->num_gpios); > - > - kfree(value_bitmap); > - bl->props.power = > - all_high ? BACKLIGHT_POWER_ON : BACKLIGHT_POWER_OFF; > - } > - > - bl->props.brightness = 1; > - > - init_brightness = backlight_get_brightness(bl); > + else if (gpiod_get_value_cansleep(gbl->gpiods->desc[0]) == 0) > + bl->props.power = BACKLIGHT_POWER_OFF; > + else > + bl->props.power = BACKLIGHT_POWER_ON; > > - for (i = 0; i < gbl->num_gpios; i++) { > - ret = gpiod_direction_output(gbl->gpiods->desc[i], > - init_brightness); > - if (ret) > - return dev_err_probe(dev, ret, > - "failed to set gpio %u direction\n", > - i); > - } > + bl->props.brightness = def_value ? 1 : 0; > > + gpio_backlight_update_status(bl); > + > platform_set_drvdata(pdev, bl); > return 0; > } > > Kindly confirm whether this approach aligns with your > expectations. As mentioned yesterday, I'd rather just review a v2 patch than this kind of meta-patch. Please send a v2 patch instead. Daniel.