1 =====================
2 LED Transient Trigger
3 =====================
4
5 The leds timer trigger does not currently have
6 a one shot timer. The current support allows f
7 specifying how long a state to be on, and the
8 to be off. The delay_on value specifies the ti
9 in on state, followed by a delay_off value tha
10 should stay in off state. The on and off cycle
11 gets deactivated. There is no provision for on
12 features that require an on or off state to be
13 the original state forever.
14
15 Without one shot timer interface, user space c
16 set a timer to hold a state, however when user
17 goes away without deactivating the timer, the
18 state permanently.
19
20 Transient trigger addresses the need for one s
21 transient trigger can be enabled and disabled
22 triggers.
23
24 When an led class device driver registers itse
25 triggers it supports and a default trigger. Du
26 routine for the default trigger gets called. D
27 class device, the LED state does not change.
28
29 When the driver unregisters, deactivation rout
30 trigger will be called, and LED state is chang
31
32 Driver suspend changes the LED state to LED_OF
33 the state. Please note that there is no explic
34 suspend and resume actions and the currently e
35 changes are suspended while the driver is in s
36 that are active at the time driver gets suspen
37 being able to actually change the LED state. O
38 start functioning again.
39
40 LED state changes are controlled using brightn
41 class device property. When brightness is set
42 echo 0 > brightness, it will result in deactiv
43
44 Transient trigger uses standard register and u
45 trigger registration, for each led class devic
46 as its default trigger, trigger activation rou
47 registration, the LED state does not change, u
48 active, in which case LED state changes to LED
49
50 During trigger unregistration, LED state gets
51
52 Transient trigger activation routine doesn't c
53 creates its properties and does its initializa
54 deactivation routine, will cancel any timer th
55 up and removes the properties it created. It w
56 non-transient state. When driver gets suspende
57 state, the LED state changes to LED_OFF.
58
59 Transient trigger can be enabled and disabled
60 devices, that support this trigger as shown be
61
62 echo transient > trigger
63 echo none > trigger
64
65 NOTE:
66 Add a new property trigger state to co
67
68 This trigger exports three properties, activat
69 transient trigger is activated these propertie
70
71 - duration allows setting timer value in msecs
72 - activate allows activating and deactivating
73 duration as needed. The initial and default
74 duration to be set after trigger activation.
75 - state allows user to specify a transient sta
76 duration.
77
78 activate
79 - one shot timer activate mechan
80 1 when activated, 0 when deact
81 default value is zero when tra
82 to allow duration to be set.
83
84 activate state indicates a tim
85 duration running.
86 deactivated state indicates th
87 running.
88
89 duration
90 - one shot timer value. When act
91 is used to start a timer that
92 get changed by the trigger unl
93 echo new_value > duration
94
95 state
96 - transient state to be held. It
97 to LED_OFF and 1 maps to LED_F
98 held for the duration of the o
99 state gets changed to the non-
100 inverse of transient state.
101 If state = LED_FULL, when the
102 go back to LED_OFF.
103 If state = LED_OFF, when the t
104 go back to LED_FULL.
105 Please note that current LED s
106 changing the state to the spec
107 Driver could map these values
108 default states it defines for
109 interface which is called from
110 interfaces to control the LED
111
112 When timer expires activate goes back to deact
113 at the set value to be used when activate is s
114 allow user app to set the time once and activa
115 specified value as needed. When timer expires,
116 non-transient state which is the inverse of th
117
118 ================= ==================
119 echo 1 > activate starts timer = dur
120 echo 0 > activate cancels currently
121 echo n > duration stores timer value
122 activate. Currentl
123 any, continues to
124 echo 0 > duration stores timer value
125 activate. Currentl
126 continues to run f
127 echo 1 > state stores desired tra
128 held for the speci
129 echo 0 > state stores desired tra
130 held for the speci
131 ================= ==================
132
133 What is not supported
134 =====================
135
136 - Timer activation is one shot and extending a
137 is not supported.
138
139 Examples
140 ========
141
142 use-case 1::
143
144 echo transient > trigger
145 echo n > duration
146 echo 1 > state
147
148 repeat the following step as needed::
149
150 echo 1 > activate - start timer = dura
151 echo 1 > activate - start timer = dura
152 echo none > trigger
153
154 This trigger is intended to be used for the fo
155
156 - Use of LED by user space app as activity in
157 - Use of LED by user space app as a kind of w
158 long as the app is alive, it can keep the L
159 the LED will be extinguished automatically.
160 - Use by any user space app that needs a tran
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