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Date:   Thu, 13 Jul 2023 11:06:19 +0100
From:   Lee Jones <lee@kernel.org>
To:     Jean-Jacques Hiblot <jjhiblot@traphandler.com>
Cc:     pavel@ucw.cz, robh+dt@kernel.org,
        krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
        linux-leds@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v10 5/5] leds: Add a multicolor LED driver to group
 monochromatic LEDs
Message-ID: <20230713100619.GJ10768@google.com>
References: <20230624084217.3079205-1-jjhiblot@traphandler.com>
 <20230624084217.3079205-6-jjhiblot@traphandler.com>
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In-Reply-To: <20230624084217.3079205-6-jjhiblot@traphandler.com>
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On Sat, 24 Jun 2023, Jean-Jacques Hiblot wrote:

> Grouping multiple monochrome LEDs into a multicolor LED device has a few
> benefits over handling the group in user-space:
> - The state of the LEDs relative to each other is consistent. In other
>   words, if 2 threads competes to set the LED to green and red, the
>   end-result cannot be black or yellow.
> - The multicolor LED as a whole can be driven through the sysfs LED
>   interface.
> 
> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@traphandler.com>
> ---
>  drivers/leds/rgb/Kconfig                 |  12 ++
>  drivers/leds/rgb/Makefile                |   1 +
>  drivers/leds/rgb/leds-group-multicolor.c | 165 +++++++++++++++++++++++
>  3 files changed, 178 insertions(+)
>  create mode 100644 drivers/leds/rgb/leds-group-multicolor.c

Reviewed-by: Lee Jones <lee@kernel.org>

> diff --git a/drivers/leds/rgb/Kconfig b/drivers/leds/rgb/Kconfig
> index 360c8679c6e2..183bccc06cf3 100644
> --- a/drivers/leds/rgb/Kconfig
> +++ b/drivers/leds/rgb/Kconfig
> @@ -2,6 +2,18 @@
>  
>  if LEDS_CLASS_MULTICOLOR
>  
> +config LEDS_GROUP_MULTICOLOR
> +	tristate "LEDs group multi-color support"
> +	depends on OF || COMPILE_TEST
> +	help
> +	  This option enables support for monochrome LEDs that are grouped
> +	  into multicolor LEDs which is useful in the case where LEDs of
> +	  different colors are physically grouped in a single multi-color LED
> +	  and driven by a controller that doesn't have multi-color support.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called leds-group-multicolor.
> +
>  config LEDS_PWM_MULTICOLOR
>  	tristate "PWM driven multi-color LED Support"
>  	depends on PWM
> diff --git a/drivers/leds/rgb/Makefile b/drivers/leds/rgb/Makefile
> index 8c01daf63f61..c11cc56384e7 100644
> --- a/drivers/leds/rgb/Makefile
> +++ b/drivers/leds/rgb/Makefile
> @@ -1,5 +1,6 @@
>  # SPDX-License-Identifier: GPL-2.0
>  
> +obj-$(CONFIG_LEDS_GROUP_MULTICOLOR)	+= leds-group-multicolor.o
>  obj-$(CONFIG_LEDS_PWM_MULTICOLOR)	+= leds-pwm-multicolor.o
>  obj-$(CONFIG_LEDS_QCOM_LPG)		+= leds-qcom-lpg.o
>  obj-$(CONFIG_LEDS_MT6370_RGB)		+= leds-mt6370-rgb.o
> diff --git a/drivers/leds/rgb/leds-group-multicolor.c b/drivers/leds/rgb/leds-group-multicolor.c
> new file mode 100644
> index 000000000000..df3e41a6272b
> --- /dev/null
> +++ b/drivers/leds/rgb/leds-group-multicolor.c
> @@ -0,0 +1,165 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Multi-color LED built with monochromatic LED devices
> + *
> + * This driver groups several monochromatic LED devices in a single multicolor LED device.
> + *
> + * Compared to handling this grouping in user-space, the benefits are:
> + * - The state of the monochromatic LED relative to each other is always consistent.
> + * - The sysfs interface of the LEDs can be used for the group as a whole.
> + *
> + * Copyright 2023 Jean-Jacques Hiblot <jjhiblot@traphandler.com>
> + */
> +
> +#include <linux/err.h>
> +#include <linux/leds.h>
> +#include <linux/led-class-multicolor.h>
> +#include <linux/math.h>
> +#include <linux/module.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/platform_device.h>
> +#include <linux/property.h>
> +
> +struct leds_multicolor {
> +	struct led_classdev_mc mc_cdev;
> +	struct led_classdev **monochromatics;
> +};
> +
> +static int leds_gmc_set(struct led_classdev *cdev, enum led_brightness brightness)
> +{
> +	struct led_classdev_mc *mc_cdev = lcdev_to_mccdev(cdev);
> +	struct leds_multicolor *priv = container_of(mc_cdev, struct leds_multicolor, mc_cdev);
> +	const unsigned int group_max_brightness = mc_cdev->led_cdev.max_brightness;
> +	int i;
> +
> +	for (i = 0; i < mc_cdev->num_colors; i++) {
> +		struct led_classdev *mono = priv->monochromatics[i];
> +		const unsigned int mono_max_brightness = mono->max_brightness;
> +		unsigned int intensity = mc_cdev->subled_info[i].intensity;
> +		int mono_brightness;
> +
> +		/*
> +		 * Scale the brightness according to relative intensity of the
> +		 * color AND the max brightness of the monochromatic LED.
> +		 */
> +		mono_brightness = DIV_ROUND_CLOSEST(brightness * intensity * mono_max_brightness,
> +						    group_max_brightness * group_max_brightness);
> +
> +		led_set_brightness(mono, mono_brightness);
> +	}
> +
> +	return 0;
> +}
> +
> +static void restore_sysfs_write_access(void *data)
> +{
> +	struct led_classdev *led_cdev = data;
> +
> +	mutex_lock(&led_cdev->led_access);
> +	led_sysfs_enable(led_cdev);
> +	mutex_unlock(&led_cdev->led_access);
> +}
> +
> +static int leds_gmc_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct led_init_data init_data = {};
> +	struct led_classdev *cdev;
> +	struct mc_subled *subled;
> +	struct leds_multicolor *priv;
> +	unsigned int max_brightness = 0;
> +	int i, ret, count = 0;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	for (;;) {
> +		struct led_classdev *led_cdev;
> +
> +		led_cdev = devm_of_led_get_optional(dev, count);
> +		if (IS_ERR(led_cdev))
> +			return dev_err_probe(dev, PTR_ERR(led_cdev), "Unable to get LED #%d",
> +					     count);
> +		if (!led_cdev)
> +			break;
> +
> +		priv->monochromatics = devm_krealloc_array(dev, priv->monochromatics,
> +					count + 1, sizeof(*priv->monochromatics),
> +					GFP_KERNEL);
> +		if (!priv->monochromatics)
> +			return -ENOMEM;
> +
> +		priv->monochromatics[count] = led_cdev;
> +
> +		max_brightness = max(max_brightness, led_cdev->max_brightness);
> +
> +		count++;
> +	}
> +
> +	subled = devm_kcalloc(dev, count, sizeof(*subled), GFP_KERNEL);
> +	if (!subled)
> +		return -ENOMEM;
> +	priv->mc_cdev.subled_info = subled;
> +
> +	for (i = 0; i < count; i++) {
> +		struct led_classdev *led_cdev = priv->monochromatics[i];
> +
> +		subled[i].color_index = led_cdev->color;
> +
> +		/* Configure the LED intensity to its maximum */
> +		subled[i].intensity = max_brightness;
> +	}
> +
> +	/* Initialise the multicolor's LED class device */
> +	cdev = &priv->mc_cdev.led_cdev;
> +	cdev->flags = LED_CORE_SUSPENDRESUME;
> +	cdev->brightness_set_blocking = leds_gmc_set;
> +	cdev->max_brightness = max_brightness;
> +	cdev->color = LED_COLOR_ID_MULTI;
> +	priv->mc_cdev.num_colors = count;
> +
> +	init_data.fwnode = dev_fwnode(dev);
> +	ret = devm_led_classdev_multicolor_register_ext(dev, &priv->mc_cdev, &init_data);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "failed to register multicolor LED for %s.\n",
> +				     cdev->name);
> +
> +	ret = leds_gmc_set(cdev, cdev->brightness);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "failed to set LED value for %s.", cdev->name);
> +
> +	for (i = 0; i < count; i++) {
> +		struct led_classdev *led_cdev = priv->monochromatics[i];
> +
> +		/* Make monochromatic LED sysfs interface read-only */
> +		mutex_lock(&led_cdev->led_access);
> +		led_sysfs_disable(led_cdev);
> +		mutex_unlock(&led_cdev->led_access);
> +
> +		/* Restore sysfs access when the multicolor LED is released */
> +		devm_add_action_or_reset(dev, restore_sysfs_write_access, led_cdev);
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id of_leds_group_multicolor_match[] = {
> +	{ .compatible = "leds-group-multicolor" },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, of_leds_group_multicolor_match);
> +
> +static struct platform_driver leds_group_multicolor_driver = {
> +	.probe		= leds_gmc_probe,
> +	.driver		= {
> +		.name	= "leds_group_multicolor",
> +		.of_match_table = of_leds_group_multicolor_match,
> +	}
> +};
> +module_platform_driver(leds_group_multicolor_driver);
> +
> +MODULE_AUTHOR("Jean-Jacques Hiblot <jjhiblot@traphandler.com>");
> +MODULE_DESCRIPTION("LEDs group multicolor driver");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:leds-group-multicolor");
> -- 
> 2.34.1
> 

-- 
Lee Jones [李琼斯]