From b8c5099b0027f013dad115b8d00f36f12cb13bb4 Mon Sep 17 00:00:00 2001 From: Hans de Goede Date: Sun, 29 Jan 2017 14:42:52 +0100 Subject: [PATCH] leds: class: Add new optional brightness_hw_changed attribute Some LEDs may have their brightness level changed autonomously (outside of kernel control) by hardware / firmware. This commit adds support for an optional brightness_hw_changed attribute to signal such changes to userspace (if a driver can detect them): What: /sys/class/leds//brightness_hw_changed Date: January 2017 KernelVersion: 4.11 Description: Last hardware set brightness level for this LED. Some LEDs may be changed autonomously by hardware/firmware. Only LEDs where this happens and the driver can detect this, will have this file. This file supports poll() to detect when the hardware changes the brightness. Reading this file will return the last brightness level set by the hardware, this may be different from the current brightness. Drivers which want to support this, simply add LED_BRIGHT_HW_CHANGED to their flags field and call led_classdev_notify_brightness_hw_changed() with the hardware set brightness when they detect a hardware / firmware triggered brightness change. Signed-off-by: Hans de Goede Acked-by: Pavel Machek Signed-off-by: Jacek Anaszewski --- Documentation/ABI/testing/sysfs-class-led | 17 +++++ Documentation/leds/leds-class.txt | 15 +++++ drivers/leds/Kconfig | 9 +++ drivers/leds/led-class.c | 76 +++++++++++++++++++++++ include/linux/leds.h | 15 +++++ 5 files changed, 132 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-class-led b/Documentation/ABI/testing/sysfs-class-led index 491cdeedc195..5f67f7ab277b 100644 --- a/Documentation/ABI/testing/sysfs-class-led +++ b/Documentation/ABI/testing/sysfs-class-led @@ -23,6 +23,23 @@ Description: If the LED does not support different brightness levels, this should be 1. +What: /sys/class/leds//brightness_hw_changed +Date: January 2017 +KernelVersion: 4.11 +Description: + Last hardware set brightness level for this LED. Some LEDs + may be changed autonomously by hardware/firmware. Only LEDs + where this happens and the driver can detect this, will have + this file. + + This file supports poll() to detect when the hardware changes + the brightness. + + Reading this file will return the last brightness level set + by the hardware, this may be different from the current + brightness. Reading this file when no hw brightness change + event has happened will return an ENODATA error. + What: /sys/class/leds//trigger Date: March 2006 KernelVersion: 2.6.17 diff --git a/Documentation/leds/leds-class.txt b/Documentation/leds/leds-class.txt index f1f7ec9f5cc5..836cb16d6f09 100644 --- a/Documentation/leds/leds-class.txt +++ b/Documentation/leds/leds-class.txt @@ -65,6 +65,21 @@ LED subsystem core exposes following API for setting brightness: blinking, returns -EBUSY if software blink fallback is enabled. +LED registration API +==================== + +A driver wanting to register a LED classdev for use by other drivers / +userspace needs to allocate and fill a led_classdev struct and then call +[devm_]led_classdev_register. If the non devm version is used the driver +must call led_classdev_unregister from its remove function before +free-ing the led_classdev struct. + +If the driver can detect hardware initiated brightness changes and thus +wants to have a brightness_hw_changed attribute then the LED_BRIGHT_HW_CHANGED +flag must be set in flags before registering. Calling +led_classdev_notify_brightness_hw_changed on a classdev not registered with +the LED_BRIGHT_HW_CHANGED flag is a bug and will trigger a WARN_ON. + Hardware accelerated blink of LEDs ================================== diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig index c621cbbb5768..275f467956ee 100644 --- a/drivers/leds/Kconfig +++ b/drivers/leds/Kconfig @@ -29,6 +29,15 @@ config LEDS_CLASS_FLASH for the flash related features of a LED device. It can be built as a module. +config LEDS_BRIGHTNESS_HW_CHANGED + bool "LED Class brightness_hw_changed attribute support" + depends on LEDS_CLASS + help + This option enables support for the brightness_hw_changed attribute + for led sysfs class devices under /sys/class/leds. + + See Documentation/ABI/testing/sysfs-class-led for details. + comment "LED drivers" config LEDS_88PM860X diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c index 326ee6e925a2..f2b0a80a62b4 100644 --- a/drivers/leds/led-class.c +++ b/drivers/leds/led-class.c @@ -103,6 +103,68 @@ static const struct attribute_group *led_groups[] = { NULL, }; +#ifdef CONFIG_LEDS_BRIGHTNESS_HW_CHANGED +static ssize_t brightness_hw_changed_show(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct led_classdev *led_cdev = dev_get_drvdata(dev); + + if (led_cdev->brightness_hw_changed == -1) + return -ENODATA; + + return sprintf(buf, "%u\n", led_cdev->brightness_hw_changed); +} + +static DEVICE_ATTR_RO(brightness_hw_changed); + +static int led_add_brightness_hw_changed(struct led_classdev *led_cdev) +{ + struct device *dev = led_cdev->dev; + int ret; + + ret = device_create_file(dev, &dev_attr_brightness_hw_changed); + if (ret) { + dev_err(dev, "Error creating brightness_hw_changed\n"); + return ret; + } + + led_cdev->brightness_hw_changed_kn = + sysfs_get_dirent(dev->kobj.sd, "brightness_hw_changed"); + if (!led_cdev->brightness_hw_changed_kn) { + dev_err(dev, "Error getting brightness_hw_changed kn\n"); + device_remove_file(dev, &dev_attr_brightness_hw_changed); + return -ENXIO; + } + + return 0; +} + +static void led_remove_brightness_hw_changed(struct led_classdev *led_cdev) +{ + sysfs_put(led_cdev->brightness_hw_changed_kn); + device_remove_file(led_cdev->dev, &dev_attr_brightness_hw_changed); +} + +void led_classdev_notify_brightness_hw_changed(struct led_classdev *led_cdev, + enum led_brightness brightness) +{ + if (WARN_ON(!led_cdev->brightness_hw_changed_kn)) + return; + + led_cdev->brightness_hw_changed = brightness; + sysfs_notify_dirent(led_cdev->brightness_hw_changed_kn); +} +EXPORT_SYMBOL_GPL(led_classdev_notify_brightness_hw_changed); +#else +static int led_add_brightness_hw_changed(struct led_classdev *led_cdev) +{ + return 0; +} +static void led_remove_brightness_hw_changed(struct led_classdev *led_cdev) +{ +} +#endif + /** * led_classdev_suspend - suspend an led_classdev. * @led_cdev: the led_classdev to suspend. @@ -204,9 +266,20 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev) dev_warn(parent, "Led %s renamed to %s due to name collision", led_cdev->name, dev_name(led_cdev->dev)); + if (led_cdev->flags & LED_BRIGHT_HW_CHANGED) { + ret = led_add_brightness_hw_changed(led_cdev); + if (ret) { + device_unregister(led_cdev->dev); + return ret; + } + } + led_cdev->work_flags = 0; #ifdef CONFIG_LEDS_TRIGGERS init_rwsem(&led_cdev->trigger_lock); +#endif +#ifdef CONFIG_LEDS_BRIGHTNESS_HW_CHANGED + led_cdev->brightness_hw_changed = -1; #endif mutex_init(&led_cdev->led_access); /* add to the list of leds */ @@ -256,6 +329,9 @@ void led_classdev_unregister(struct led_classdev *led_cdev) flush_work(&led_cdev->set_brightness_work); + if (led_cdev->flags & LED_BRIGHT_HW_CHANGED) + led_remove_brightness_hw_changed(led_cdev); + device_unregister(led_cdev->dev); down_write(&leds_list_lock); diff --git a/include/linux/leds.h b/include/linux/leds.h index 569cb531094c..c7711539888b 100644 --- a/include/linux/leds.h +++ b/include/linux/leds.h @@ -13,6 +13,7 @@ #define __LINUX_LEDS_H_INCLUDED #include +#include #include #include #include @@ -46,6 +47,7 @@ struct led_classdev { #define LED_DEV_CAP_FLASH (1 << 18) #define LED_HW_PLUGGABLE (1 << 19) #define LED_PANIC_INDICATOR (1 << 20) +#define LED_BRIGHT_HW_CHANGED (1 << 21) /* set_brightness_work / blink_timer flags, atomic, private. */ unsigned long work_flags; @@ -110,6 +112,11 @@ struct led_classdev { bool activated; #endif +#ifdef CONFIG_LEDS_BRIGHTNESS_HW_CHANGED + int brightness_hw_changed; + struct kernfs_node *brightness_hw_changed_kn; +#endif + /* Ensures consistent access to the LED Flash Class device */ struct mutex led_access; }; @@ -422,4 +429,12 @@ static inline void ledtrig_cpu(enum cpu_led_event evt) } #endif +#ifdef CONFIG_LEDS_BRIGHTNESS_HW_CHANGED +extern void led_classdev_notify_brightness_hw_changed( + struct led_classdev *led_cdev, enum led_brightness brightness); +#else +static inline void led_classdev_notify_brightness_hw_changed( + struct led_classdev *led_cdev, enum led_brightness brightness) { } +#endif + #endif /* __LINUX_LEDS_H_INCLUDED */ -- 2.20.1