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 <[email protected]>
> ---
> 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.
> };
>
> static int gpio_backlight_update_status(struct backlight_device *bl)
> {
> struct gpio_backlight *gbl = bl_get_data(bl);
> + unsigned int i;
> + int br = backlight_get_brightness(bl);
>
> - gpiod_set_value_cansleep(gbl->gpiod, backlight_get_brightness(bl));
> + for (i = 0; i < gbl->num_gpios; i++)
> + gpiod_set_value_cansleep(gbl->gpiods[i], br);
>
> return 0;
> }
> @@ -52,6 +56,7 @@ static int gpio_backlight_probe(struct platform_device
> *pdev)
> struct backlight_device *bl;
> struct gpio_backlight *gbl;
> int ret, init_brightness, def_value;
> + unsigned int i;
>
> gbl = devm_kzalloc(dev, sizeof(*gbl), GFP_KERNEL);
> if (gbl == NULL)
> @@ -62,10 +67,22 @@ static int gpio_backlight_probe(struct platform_device
> *pdev)
>
> def_value = device_property_read_bool(dev, "default-on");
>
> - 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");
> + gbl->num_gpios = gpiod_count(dev, NULL);
> + if (gbl->num_gpios == 0)
> + return dev_err_probe(dev, -EINVAL,
> + "The gpios parameter is missing or invalid\n");
> + gbl->gpiods = devm_kcalloc(dev, gbl->num_gpios, sizeof(*gbl->gpiods),
> + GFP_KERNEL);
> + if (!gbl->gpiods)
> + return -ENOMEM;
This is definitely easier if you simply use devm_get_array().
> +
> + for (i = 0; i < gbl->num_gpios; i++) {
> + gbl->gpiods[i] =
> + devm_gpiod_get_index(dev, NULL, i, GPIOD_ASIS);
> + if (IS_ERR(gbl->gpiods[i]))
> + return dev_err_probe(dev, PTR_ERR(gbl->gpiods[i]),
> + "Failed to get GPIO at index %u\n", i);
> + }
>
> memset(&props, 0, sizeof(props));
> props.type = BACKLIGHT_RAW;
> @@ -78,22 +95,34 @@ 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 if (gpiod_get_value_cansleep(gbl->gpiod) == 0)
> - bl->props.power = BACKLIGHT_POWER_OFF;
> - else
> - bl->props.power = BACKLIGHT_POWER_ON;
> + : BACKLIGHT_POWER_OFF;
> + } else {
> + bool all_high = true;
> +
> + for (i = 0; i < gbl->num_gpios; i++) {
> + if (gpiod_get_value_cansleep(gbl->gpiods[i]) != 0) {
Why is there a != here?
> + all_high = false;
> + break;
> + }
> + }
> +
> + bl->props.power =
> + all_high ? BACKLIGHT_POWER_ON : BACKLIGHT_POWER_OFF;
> + }
>
> 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;
> +
> + for (i = 0; i < gbl->num_gpios; i++) {
> + ret = gpiod_direction_output(gbl->gpiods[i], init_brightness);
> + if (ret)
> + return dev_err_probe(dev, ret,
> + "failed to set gpio %u direction\n",
> + i);
> }
>
> platform_set_drvdata(pdev, bl);
Daniel.
