Revision 0255004d2a8eb1575e1b9f9fabe0715a7a44288c authored by Alexander Potapenko on 13 April 2023, 12:20:33 UTC, committed by Alexander Potapenko on 17 April 2023, 07:52:33 UTC
To prevent errors when vmap_pages_range_noflush() or __vmap_pages_range_noflush() silently fail (see the link below for an example), annotate them with __must_check so that the callers do not unconditionally assume the mapping succeeded. Reported-by: Dipanjan Das <mail.dipanjan.das@gmail.com> Link: https://lore.kernel.org/linux-mm/CANX2M5ZRrRA64k0hOif02TjmY9kbbO2aCBPyq79es34RXZ=cAw@mail.gmail.com/ Signed-off-by: Alexander Potapenko <glider@google.com>
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ledtrig-oneshot.rst
====================
One-shot LED Trigger
====================
This is a LED trigger useful for signaling the user of an event where there are
no clear trap points to put standard led-on and led-off settings. Using this
trigger, the application needs only to signal the trigger when an event has
happened, than the trigger turns the LED on and than keeps it off for a
specified amount of time.
This trigger is meant to be usable both for sporadic and dense events. In the
first case, the trigger produces a clear single controlled blink for each
event, while in the latter it keeps blinking at constant rate, as to signal
that the events are arriving continuously.
A one-shot LED only stays in a constant state when there are no events. An
additional "invert" property specifies if the LED has to stay off (normal) or
on (inverted) when not rearmed.
The trigger can be activated from user space on led class devices as shown
below::
echo oneshot > trigger
This adds sysfs attributes to the LED that are documented in:
Documentation/ABI/testing/sysfs-class-led-trigger-oneshot
Example use-case: network devices, initialization::
echo oneshot > trigger # set trigger for this led
echo 33 > delay_on # blink at 1 / (33 + 33) Hz on continuous traffic
echo 33 > delay_off
interface goes up::
echo 1 > invert # set led as normally-on, turn the led on
packet received/transmitted::
echo 1 > shot # led starts blinking, ignored if already blinking
interface goes down::
echo 0 > invert # set led as normally-off, turn the led off
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