path: root/Documentation/leds
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authorLinus Torvalds <>2015-07-01 19:09:11 -0700
committerLinus Torvalds <>2015-07-01 19:09:11 -0700
commit13d45f79a2af84de9083310db58b309a61065208 (patch)
tree06968d83ed6e5e23e1f729cf6f096f9a79f14f72 /Documentation/leds
parent05fde26a943a9c55d8b498d97bb49d3d207e5069 (diff)
parentb67893206fc0a0e8af87130e67f3d8ae553fc87c (diff)
Merge branch 'for-next' of git://
Pull LED subsystem updates from Bryan Wu: "In this cycle, we finished to merge patches for LED Flash class driver. Other than that we have some bug fixes and new drivers for LED controllers" * 'for-next' of git:// (33 commits) leds:lp55xx: fix firmware loading error leds: fix max77693-led build errors leds: fix aat1290 build errors leds: aat1290: pass flags parameter to devm_gpiod_get leds: ktd2692: pass flags parameter to devm_gpiod_get drivers/leds: don't use module_init in non-modular leds-cobalt-raq.c leds: aat1290: add support for V4L2 Flash sub-device DT: aat1290: Document handling external strobe sources leds: max77693: add support for V4L2 Flash sub-device media: Add registration helpers for V4L2 flash sub-devices v4l: async: Add a pointer to of_node to struct v4l2_subdev, match it Documentation: leds: Add description of v4l2-flash sub-device leds: add BCM6358 LED driver leds: add DT binding for BCM6358 LED controller leds: fix brightness changing when software blinking is active Documentation: leds-lp5523: describe master fader attributes leds: lp5523: add master_fader support leds: leds-gpio: Allow compile test if !GPIOLIB leds: leds-gpio: Add missing #include <linux/of.h> gpiolib: Add missing dummies for the unified device properties interface ...
Diffstat (limited to 'Documentation/leds')
2 files changed, 81 insertions, 0 deletions
diff --git a/Documentation/leds/leds-class-flash.txt b/Documentation/leds/leds-class-flash.txt
index 19bb67355424..8da3c6f4b60b 100644
--- a/Documentation/leds/leds-class-flash.txt
+++ b/Documentation/leds/leds-class-flash.txt
@@ -20,3 +20,54 @@ Following sysfs attributes are exposed for controlling flash LED devices:
- max_flash_timeout
- flash_strobe
- flash_fault
+V4L2 flash wrapper for flash LEDs
+A LED subsystem driver can be controlled also from the level of VideoForLinux2
+subsystem. In order to enable this CONFIG_V4L2_FLASH_LED_CLASS symbol has to
+be defined in the kernel config.
+The driver must call the v4l2_flash_init function to get registered in the
+V4L2 subsystem. The function takes six arguments:
+- dev : flash device, e.g. an I2C device
+- of_node : of_node of the LED, may be NULL if the same as device's
+- fled_cdev : LED flash class device to wrap
+- iled_cdev : LED flash class device representing indicator LED associated with
+ fled_cdev, may be NULL
+- ops : V4L2 specific ops
+ * external_strobe_set - defines the source of the flash LED strobe -
+ V4L2_CID_FLASH_STROBE control or external source, typically
+ a sensor, which makes it possible to synchronise the flash
+ strobe start with exposure start,
+ * intensity_to_led_brightness and led_brightness_to_intensity - perform
+ enum led_brightness <-> V4L2 intensity conversion in a device
+ specific manner - they can be used for devices with non-linear
+ LED current scale.
+- config : configuration for V4L2 Flash sub-device
+ * dev_name - the name of the media entity, unique in the system,
+ * flash_faults - bitmask of flash faults that the LED flash class
+ device can report; corresponding LED_FAULT* bit definitions are
+ available in <linux/led-class-flash.h>,
+ * torch_intensity - constraints for the LED in TORCH mode
+ in microamperes,
+ * indicator_intensity - constraints for the indicator LED
+ in microamperes,
+ * has_external_strobe - determines whether the flash strobe source
+ can be switched to external,
+On remove the v4l2_flash_release function has to be called, which takes one
+argument - struct v4l2_flash pointer returned previously by v4l2_flash_init.
+This function can be safely called with NULL or error pointer argument.
+Please refer to drivers/leds/leds-max77693.c for an exemplary usage of the
+v4l2 flash wrapper.
+Once the V4L2 sub-device is registered by the driver which created the Media
+controller device, the sub-device node acts just as a node of a native V4L2
+flash API device would. The calls are simply routed to the LED flash API.
+Opening the V4L2 flash sub-device makes the LED subsystem sysfs interface
+unavailable. The interface is re-enabled after the V4L2 flash sub-device
+is closed.
diff --git a/Documentation/leds/leds-lp5523.txt b/Documentation/leds/leds-lp5523.txt
index 5b3e91d4ac59..0dbbd279c9b9 100644
--- a/Documentation/leds/leds-lp5523.txt
+++ b/Documentation/leds/leds-lp5523.txt
@@ -49,6 +49,36 @@ There are two ways to run LED patterns.
2) Firmware interface - LP55xx common interface
For the details, please refer to 'firmware' section in leds-lp55xx.txt
+LP5523 has three master faders. If a channel is mapped to one of
+the master faders, its output is dimmed based on the value of the master
+For example,
+ echo "123000123" > master_fader_leds
+creates the following channel-fader mappings:
+ channel 0,6 to master_fader1
+ channel 1,7 to master_fader2
+ channel 2,8 to master_fader3
+Then, to have 25% of the original output on channel 0,6:
+ echo 64 > master_fader1
+To have 0% of the original output (i.e. no output) channel 1,7:
+ echo 0 > master_fader2
+To have 100% of the original output (i.e. no dimming) on channel 2,8:
+ echo 255 > master_fader3
+To clear all master fader controls:
+ echo "000000000" > master_fader_leds
Selftest uses always the current from the platform data.
Each channel contains led current settings.