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Message-ID: <20230713100619.GJ10768@google.com>
Date: Thu, 13 Jul 2023 11:06:19 +0100
From: Lee Jones <lee@...nel.org>
To: Jean-Jacques Hiblot <jjhiblot@...phandler.com>
Cc: pavel@....cz, robh+dt@...nel.org,
krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 5/5] leds: Add a multicolor LED driver to group
monochromatic LEDs
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@...phandler.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@...nel.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@...phandler.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@...phandler.com>");
> +MODULE_DESCRIPTION("LEDs group multicolor driver");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:leds-group-multicolor");
> --
> 2.34.1
>
--
Lee Jones [李琼斯]
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