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1f70cb4045
Documentation of sysfs interface should be in ABI in the first place. This moves relevant part of documentation and mentions where to look for it. Fix trivial typos whilst we are at it. Signed-off-by: Rafał Miłecki <rafal@milecki.pl> Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
44 lines
1.5 KiB
Plaintext
44 lines
1.5 KiB
Plaintext
One-shot LED Trigger
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====================
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This is a LED trigger useful for signaling the user of an event where there are
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no clear trap points to put standard led-on and led-off settings. Using this
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trigger, the application needs only to signal the trigger when an event has
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happened, than the trigger turns the LED on and than keeps it off for a
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specified amount of time.
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This trigger is meant to be usable both for sporadic and dense events. In the
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first case, the trigger produces a clear single controlled blink for each
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event, while in the latter it keeps blinking at constant rate, as to signal
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that the events are arriving continuously.
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A one-shot LED only stays in a constant state when there are no events. An
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additional "invert" property specifies if the LED has to stay off (normal) or
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on (inverted) when not rearmed.
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The trigger can be activated from user space on led class devices as shown
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below:
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echo oneshot > trigger
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This adds sysfs attributes to the LED that are documented in:
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Documentation/ABI/testing/sysfs-class-led-trigger-oneshot
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Example use-case: network devices, initialization:
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echo oneshot > trigger # set trigger for this led
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echo 33 > delay_on # blink at 1 / (33 + 33) Hz on continuous traffic
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echo 33 > delay_off
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interface goes up:
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echo 1 > invert # set led as normally-on, turn the led on
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packet received/transmitted:
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echo 1 > shot # led starts blinking, ignored if already blinking
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interface goes down
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echo 0 > invert # set led as normally-off, turn the led off
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