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SubjectRe: [PATCH v8 5/5] backlight: add led-backlight driver
Hi,

On Thu, Oct 03, 2019 at 10:28:12AM +0200, Jean-Jacques Hiblot wrote:
> From: Tomi Valkeinen <tomi.valkeinen@ti.com>
>
> This patch adds a led-backlight driver (led_bl), which is similar to
> pwm_bl except the driver uses a LED class driver to adjust the
> brightness in the HW. Multiple LEDs can be used for a single backlight.
>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
> Acked-by: Pavel Machek <pavel@ucw.cz>
> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
> ---

Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.com>

(with some suggestions below)

> drivers/video/backlight/Kconfig | 7 +
> drivers/video/backlight/Makefile | 1 +
> drivers/video/backlight/led_bl.c | 260 +++++++++++++++++++++++++++++++
> 3 files changed, 268 insertions(+)
> create mode 100644 drivers/video/backlight/led_bl.c
>
> diff --git a/drivers/video/backlight/Kconfig b/drivers/video/backlight/Kconfig
> index 8b081d61773e..585a1787618c 100644
> --- a/drivers/video/backlight/Kconfig
> +++ b/drivers/video/backlight/Kconfig
> @@ -458,6 +458,13 @@ config BACKLIGHT_RAVE_SP
> help
> Support for backlight control on RAVE SP device.
>
> +config BACKLIGHT_LED
> + tristate "Generic LED based Backlight Driver"
> + depends on LEDS_CLASS && OF
> + help
> + If you have a LCD backlight adjustable by LED class driver, say Y
> + to enable this driver.
> +
> endif # BACKLIGHT_CLASS_DEVICE
>
> endmenu
> diff --git a/drivers/video/backlight/Makefile b/drivers/video/backlight/Makefile
> index 63c507c07437..2a67642966a5 100644
> --- a/drivers/video/backlight/Makefile
> +++ b/drivers/video/backlight/Makefile
> @@ -57,3 +57,4 @@ obj-$(CONFIG_BACKLIGHT_TPS65217) += tps65217_bl.o
> obj-$(CONFIG_BACKLIGHT_WM831X) += wm831x_bl.o
> obj-$(CONFIG_BACKLIGHT_ARCXCNN) += arcxcnn_bl.o
> obj-$(CONFIG_BACKLIGHT_RAVE_SP) += rave-sp-backlight.o
> +obj-$(CONFIG_BACKLIGHT_LED) += led_bl.o
> diff --git a/drivers/video/backlight/led_bl.c b/drivers/video/backlight/led_bl.c
> new file mode 100644
> index 000000000000..3f66549997c8
> --- /dev/null
> +++ b/drivers/video/backlight/led_bl.c
> @@ -0,0 +1,260 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2015-2019 Texas Instruments Incorporated - http://www.ti.com/
> + * Author: Tomi Valkeinen <tomi.valkeinen@ti.com>
> + *
> + * Based on pwm_bl.c
> + */
> +
> +#include <linux/backlight.h>
> +#include <linux/leds.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +
> +struct led_bl_data {
> + struct device *dev;
> + struct backlight_device *bl_dev;
> + struct led_classdev **leds;
> + bool enabled;
> + int nb_leds;
> + unsigned int *levels;
> + unsigned int default_brightness;
> + unsigned int max_brightness;
> +};
> +
> +static void led_bl_set_brightness(struct led_bl_data *priv, int level)
> +{
> + int i;
> + int bkl_brightness;
> +
> + if (priv->levels)
> + bkl_brightness = priv->levels[level];
> + else
> + bkl_brightness = level;
> +
> + for (i = 0; i < priv->nb_leds; i++)
> + led_set_brightness(priv->leds[i], bkl_brightness);
> +
> + priv->enabled = true;
> +}
> +
> +static void led_bl_power_off(struct led_bl_data *priv)
> +{
> + int i;
> +
> + if (!priv->enabled)
> + return;
> +
> + for (i = 0; i < priv->nb_leds; i++)
> + led_set_brightness(priv->leds[i], LED_OFF);
> +
> + priv->enabled = false;
> +}
> +
> +static int led_bl_update_status(struct backlight_device *bl)
> +{
> + struct led_bl_data *priv = bl_get_data(bl);
> + int brightness = bl->props.brightness;
> +
> + if (bl->props.power != FB_BLANK_UNBLANK ||
> + bl->props.fb_blank != FB_BLANK_UNBLANK ||
> + bl->props.state & BL_CORE_FBBLANK)
> + brightness = 0;
> +
> + if (brightness > 0)
> + led_bl_set_brightness(priv, brightness);
> + else
> + led_bl_power_off(priv);
> +
> + return 0;
> +}
> +
> +static const struct backlight_ops led_bl_ops = {
> + .update_status = led_bl_update_status,
> +};
> +
> +static int led_bl_get_leds(struct device *dev,
> + struct led_bl_data *priv)
> +{
> + int i, nb_leds, ret;
> + struct device_node *node = dev->of_node;
> + struct led_classdev **leds;
> + unsigned int max_brightness;
> + unsigned int default_brightness;
> +
> + ret = of_count_phandle_with_args(node, "leds", NULL);
> + if (ret < 0) {
> + dev_err(dev, "Unable to get led count\n");
> + return -EINVAL;
> + }
> +
> + nb_leds = ret;
> + if (nb_leds < 1) {
> + dev_err(dev, "At least one LED must be specified!\n");
> + return -EINVAL;
> + }
> +
> + leds = devm_kzalloc(dev, sizeof(struct led_classdev *) * nb_leds,
> + GFP_KERNEL);
> + if (!leds)
> + return -ENOMEM;
> +
> + for (i = 0; i < nb_leds; i++) {
> + leds[i] = devm_of_led_get(dev, i);
> + if (IS_ERR(leds[i]))
> + return PTR_ERR(leds[i]);
> + }
> +
> + /* check that the LEDs all have the same brightness range */
> + max_brightness = leds[0]->max_brightness;
> + for (i = 1; i < nb_leds; i++) {
> + if (max_brightness != leds[i]->max_brightness) {
> + dev_err(dev, "LEDs must have identical ranges\n");
> + return -EINVAL;
> + }
> + }
> +
> + /* get the default brightness from the first LED from the list */
> + default_brightness = leds[0]->brightness;
> +
> + priv->nb_leds = nb_leds;
> + priv->leds = leds;
> + priv->max_brightness = max_brightness;
> + priv->default_brightness = default_brightness;
> +
> + return 0;
> +}
> +
> +static int led_bl_parse_levels(struct device *dev,
> + struct led_bl_data *priv)
> +{
> + struct device_node *node = dev->of_node;
> + int num_levels;
> + u32 value;
> + int ret;
> +
> + if (!node)
> + return -ENODEV;
> +
> + num_levels = of_property_count_u32_elems(node, "brightness-levels");
> + if (num_levels > 1) {
> + int i;
> + unsigned int db;
> + u32 *levels = NULL;
> +
> + levels = devm_kzalloc(dev, sizeof(u32) * num_levels,
> + GFP_KERNEL);
> + if (!levels)
> + return -ENOMEM;
> +
> + ret = of_property_read_u32_array(node, "brightness-levels",
> + levels,
> + num_levels);
> + if (ret < 0)
> + return ret;
> +
> + /*
> + * Try to map actual LED brightness to backlight brightness
> + * level
> + */
> + db = priv->default_brightness;
> + for (i = 0 ; i < num_levels; i++) {
> + if ((i && db > levels[i-1]) && db <= levels[i])
> + break;
> + }
> + priv->default_brightness = i;
> + priv->max_brightness = num_levels - 1;
> + priv->levels = levels;
> + } else if (num_levels >= 0)
> + dev_warn(dev, "Not enough levels defined\n");
> +
> + ret = of_property_read_u32(node, "default-brightness-level", &value);
> + if (!ret && value <= priv->max_brightness)
> + priv->default_brightness = value;
> + else if (!ret && value > priv->max_brightness)
> + dev_warn(dev, "Invalid default brightness. Ignoring it\n");
> +
> + return 0;
> +}
> +
> +static int led_bl_probe(struct platform_device *pdev)
> +{
> + struct backlight_properties props;
> + struct led_bl_data *priv;
> + int ret, i;
> +
> + priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> + if (!priv)
> + return -ENOMEM;
> +
> + platform_set_drvdata(pdev, priv);
> +
> + priv->dev = &pdev->dev;
> +
> + ret = led_bl_get_leds(&pdev->dev, priv);
> + if (ret)
> + return ret;
> +
> + ret = led_bl_parse_levels(&pdev->dev, priv);
> + if (ret < 0) {
> + dev_err(&pdev->dev, "Failed to parse DT data\n");
> + return ret;
> + }
> +
> + memset(&props, 0, sizeof(struct backlight_properties));
> + props.type = BACKLIGHT_RAW;
> + props.max_brightness = priv->max_brightness;
> + props.brightness = priv->default_brightness;
> + props.power = (priv->default_brightness > 0) ? FB_BLANK_POWERDOWN :
> + FB_BLANK_UNBLANK;
> + priv->bl_dev = backlight_device_register(dev_name(&pdev->dev),
> + &pdev->dev, priv, &led_bl_ops, &props);
> + if (IS_ERR(priv->bl_dev)) {
> + dev_err(&pdev->dev, "Failed to register backlight\n");
> + return PTR_ERR(priv->bl_dev);
> + }
> +
> + for (i = 0; i < priv->nb_leds; i++)
> + led_sysfs_disable(priv->leds[i]);

I suggest to restructure:

1. call led_sysfs_disable

2. use devm_add_action_or_reset() to register the
led_sysfs_enable loop

3. use devm_backlight_device_register() to register BL

4. drop the remove function

> +
> + backlight_update_status(priv->bl_dev);
> +
> + return 0;
> +}
> +
> +static int led_bl_remove(struct platform_device *pdev)
> +{
> + struct led_bl_data *priv = platform_get_drvdata(pdev);
> + struct backlight_device *bl = priv->bl_dev;
> + int i;
> +
> + backlight_device_unregister(bl);
> +
> + led_bl_power_off(priv);
> + for (i = 0; i < priv->nb_leds; i++)
> + led_sysfs_enable(priv->leds[i]);
> +
> + return 0;
> +}
> +
> +static const struct of_device_id led_bl_of_match[] = {
> + { .compatible = "led-backlight" },
> + { }
> +};
> +
> +MODULE_DEVICE_TABLE(of, led_bl_of_match);
> +
> +static struct platform_driver led_bl_driver = {
> + .driver = {
> + .name = "led-backlight",
> + .of_match_table = of_match_ptr(led_bl_of_match),

You should drop of_match_ptr(). Since the driver depends on OF,
it will always simply return led_bl_of_match.

(Also after removing the OF dependency from the driver it would
either require led_bl_of_match to be marked __maybe_unused or
moving it into a #if CONFIG_OF area to avoid warnings.)

-- Sebastian

> + },
> + .probe = led_bl_probe,
> + .remove = led_bl_remove,
> +};
> +
> +module_platform_driver(led_bl_driver);
> +
> +MODULE_DESCRIPTION("LED based Backlight Driver");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:led-backlight");
> --
> 2.17.1
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
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