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[82.37.195.13]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4806cdd79c7sm54470645e9.2.2026.01.28.02.57.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Jan 2026 02:57:59 -0800 (PST) Date: Wed, 28 Jan 2026 10:57:55 +0000 From: Daniel Thompson To: Sudarshan Shetty 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 v2 2/2] backlight: gpio: add support for multiple GPIOs for backlight control Message-ID: References: <20260120125036.2203995-1-tessolveupstream@gmail.com> <20260120125036.2203995-3-tessolveupstream@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@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: <20260120125036.2203995-3-tessolveupstream@gmail.com> On Tue, Jan 20, 2026 at 06:20:36PM +0530, Sudarshan Shetty wrote: > The gpio-backlight driver currently supports only a single GPIO to > enable or disable a backlight device. Some panels require multiple > enable GPIOs to be asserted together. > > Extend the driver to support an array of GPIOs for a single backlight > instance. All configured GPIOs are toggled together based on the > backlight state. > > Existing single-GPIO Device Tree users remain unaffected. > > Signed-off-by: Sudarshan Shetty > --- > drivers/video/backlight/gpio_backlight.c | 66 ++++++++++++++++-------- > 1 file changed, 45 insertions(+), 21 deletions(-) > > diff --git a/drivers/video/backlight/gpio_backlight.c b/drivers/video/backlight/gpio_backlight.c > index 728a546904b0..11d21de82cf5 100644 > --- a/drivers/video/backlight/gpio_backlight.c > +++ b/drivers/video/backlight/gpio_backlight.c > @@ -14,17 +14,29 @@ > #include > #include > #include > +#include > > struct gpio_backlight { > struct device *dev; > - struct gpio_desc *gpiod; > + struct gpio_descs *gpiods; > + 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->gpiods->ndescs; > + int br = backlight_get_brightness(bl); > > - gpiod_set_value_cansleep(gbl->gpiod, backlight_get_brightness(bl)); > + if (br) > + bitmap_fill(gbl->bitmap, n); > + else > + bitmap_zero(gbl->bitmap, n); > + > + gpiod_set_array_value_cansleep(n, > + gbl->gpiods->desc, > + gbl->gpiods->info, > + gbl->bitmap); > > return 0; > } > @@ -48,26 +60,43 @@ 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 = { }; This change is unrelated to the patch description. Do not "hide" changes like this. It you want to replace the memset() it's better to send a separate patch. > struct backlight_device *bl; > struct gpio_backlight *gbl; > - int ret, init_brightness, def_value; > + 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) Again, this change is unrelated to the patch description. Do not include changes that are not described in the patch description. > return -ENOMEM; > > if (pdata) > gbl->dev = pdata->dev; > > def_value = device_property_read_bool(dev, "default-on"); > + flags = def_value ? GPIOD_OUT_HIGH : GPIOD_OUT_LOW; > + > + gbl->gpiods = devm_gpiod_get_array(dev, NULL, flags); How is it safe to transition from GPIOD_ASIS to GPIOD_OUT_LOW here? Forcing the backlight off if the default-on property is not present will prevent the backlight state being properly inherited from the bootloader. > + if (IS_ERR(gbl->gpiods)) { > + if (PTR_ERR(gbl->gpiods) == -ENODEV) > + return dev_err_probe(dev, -EINVAL, > + "The gpios parameter is missing or invalid\n"); > + return PTR_ERR(gbl->gpiods); > + } > > - gbl->gpiod = devm_gpiod_get(dev, NULL, GPIOD_ASIS); > - if (IS_ERR(gbl->gpiod)) > - return dev_err_probe(dev, PTR_ERR(gbl->gpiod), > - "The gpios parameter is missing or invalid\n"); > + n = gbl->gpiods->ndescs; > + if (!n) > + return dev_err_probe(dev, -EINVAL, > + "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, > @@ -81,21 +110,16 @@ static int gpio_backlight_probe(struct platform_device *pdev) > 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 if (gpiod_get_value_cansleep(gbl->gpiod) == 0) > + : BACKLIGHT_POWER_OFF; > + else if (gpiod_get_value_cansleep(gbl->gpiods->desc[0]) == 0) This logic is broken. This code path needs to be taken is *any* GPIO is low (and, as mentioned, the initial GPIO state must be GPIOD_ASIS). > bl->props.power = BACKLIGHT_POWER_OFF; > else > bl->props.power = BACKLIGHT_POWER_ON; > > - bl->props.brightness = 1; > - > - init_brightness = backlight_get_brightness(bl); > - ret = gpiod_direction_output(gbl->gpiod, init_brightness); > - if (ret) { > - dev_err(dev, "failed to set initial brightness\n"); > - return ret; > - } > + bl->props.brightness = def_value ? 1 : 0; > > + gpio_backlight_update_status(bl); > + > platform_set_drvdata(pdev, bl); > return 0; > } Daniel.