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This driver creates a userspace leds driver similar to uinput. New LEDs are created by opening /dev/uleds and writing a uleds_user_dev struct. A new LED class device is registered with the name given in the struct. Reading will return a single byte that is the current brightness. The poll() syscall is also supported. It will be triggered whenever the brightness changes. Closing the file handle to /dev/uleds will remove the leds class device. Signed-off-by: David Lechner <david@lechnology.com> Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
37 lines
1.2 KiB
Plaintext
37 lines
1.2 KiB
Plaintext
Userspace LEDs
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==============
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The uleds driver supports userspace LEDs. This can be useful for testing
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triggers and can also be used to implement virtual LEDs.
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Usage
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=====
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When the driver is loaded, a character device is created at /dev/uleds. To
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create a new LED class device, open /dev/uleds and write a uleds_user_dev
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structure to it (found in kernel public header file linux/uleds.h).
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#define LED_MAX_NAME_SIZE 64
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struct uleds_user_dev {
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char name[LED_MAX_NAME_SIZE];
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};
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A new LED class device will be created with the name given. The name can be
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any valid sysfs device node name, but consider using the LED class naming
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convention of "devicename:color:function".
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The current brightness is found by reading a single byte from the character
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device. Values are unsigned: 0 to 255. Reading will block until the brightness
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changes. The device node can also be polled to notify when the brightness value
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changes.
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The LED class device will be removed when the open file handle to /dev/uleds
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is closed.
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Multiple LED class devices are created by opening additional file handles to
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/dev/uleds.
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See tools/leds/uledmon.c for an example userspace program.
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