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authorKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2012-09-12 11:14:33 -0400
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2012-09-12 11:14:33 -0400
commit25a765b7f05cb8460fa01b54568894b20e184862 (patch)
tree0b56db57b4d9f912393ab303c269e0fe6cdf8635 /Documentation/leds/ledtrig-oneshot.txt
parent9d2be9287107695708e6aae5105a8a518a6cb4d0 (diff)
parent64282278989d5b0398dcb3ba7904cb00c621dc35 (diff)
Merge branch 'x86/platform' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into stable/for-linus-3.7
* 'x86/platform' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (9690 commits) x86: Document x86_init.paging.pagetable_init() x86: xen: Cleanup and remove x86_init.paging.pagetable_setup_done() x86: Move paging_init() call to x86_init.paging.pagetable_init() x86: Rename pagetable_setup_start() to pagetable_init() x86: Remove base argument from x86_init.paging.pagetable_setup_start Linux 3.6-rc5 HID: tpkbd: work even if the new Lenovo Keyboard driver is not configured Remove user-triggerable BUG from mpol_to_str xen/pciback: Fix proper FLR steps. uml: fix compile error in deliver_alarm() dj: memory scribble in logi_dj Fix order of arguments to compat_put_time[spec|val] xen: Use correct masking in xen_swiotlb_alloc_coherent. xen: fix logical error in tlb flushing xen/p2m: Fix one-off error in checking the P2M tree directory. powerpc: Don't use __put_user() in patch_instruction powerpc: Make sure IPI handlers see data written by IPI senders powerpc: Restore correct DSCR in context switch powerpc: Fix DSCR inheritance in copy_thread() powerpc: Keep thread.dscr and thread.dscr_inherit in sync ...
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+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 the following sysfs attributes to the LED:
+
+ delay_on - specifies for how many milliseconds the LED has to stay at
+ LED_FULL brightness after it has been armed.
+ Default to 100 ms.
+
+ delay_off - specifies for how many milliseconds the LED has to stay at
+ LED_OFF brightness after it has been armed.
+ Default to 100 ms.
+
+ invert - reverse the blink logic. If set to 0 (default) blink on for delay_on
+ ms, then blink off for delay_off ms, leaving the LED normally off. If
+ set to 1, blink off for delay_off ms, then blink on for delay_on ms,
+ leaving the LED normally on.
+ Setting this value also immediately change the LED state.
+
+ shot - write any non-empty string to signal an events, this starts a blink
+ sequence if not already running.
+
+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