1 .. SPDX-License-Identifier: GPL-2.0-only
2
3 Virtual GPIO Consumer
4 =====================
5
6 The virtual GPIO Consumer module allows users
7 that request GPIOs and then control their beha
8 consumer devices can be instantiated from devi
9
10 A virtual consumer uses the driver-facing GPIO
11 automated tests driven by user-space. The GPIO
12 ``gpiod_get_array()`` and so we support multip
13
14 Creating GPIO consumers
15 -----------------------
16
17 The gpio-consumer module registers a configfs
18 ``'gpio-virtuser'``. For details of the config
19 the configfs documentation.
20
21 The user can create a hierarchy of configfs gr
22 values of exposed attributes. Once the consume
23 will be translated to appropriate device prope
24
25 **Group:** ``/config/gpio-virtuser``
26
27 This is the top directory of the gpio-consumer
28
29 **Group:** ``/config/gpio-consumer/example-nam
30
31 **Attribute:** ``/config/gpio-consumer/example
32
33 **Attribute:** ``/config/gpio-consumer/example
34
35 This is a directory representing a GPIO consum
36
37 The read-only ``dev_name`` attribute exposes t
38 appear in the system on the platform bus. This
39 associated debugfs directory under
40 ``/sys/kernel/debug/gpio-virtuser/$dev_name``.
41
42 The ``'live'`` attribute allows to trigger the
43 once it's fully configured. The accepted value
44 virtual device and ``'0'`` to disable and tear
45
46 Creating GPIO lookup tables
47 ---------------------------
48
49 Users can create a number of configfs groups u
50
51 **Group:** ``/config/gpio-consumer/example-nam
52
53 The ``'con_id'`` directory represents a single
54 to the ``'con_id'`` argument of the ``gpiod_ge
55 ``con_id`` == ``'reset'`` maps to the ``reset-
56
57 Users can assign a number of GPIOs to each loo
58 with a user-defined name under the ``'con_id'`
59
60 **Attribute:** ``/config/gpio-consumer/example
61
62 **Attribute:** ``/config/gpio-consumer/example
63
64 **Attribute:** ``/config/gpio-consumer/example
65
66 **Attribute:** ``/config/gpio-consumer/example
67
68 **Attribute:** ``/config/gpio-consumer/example
69
70 **Attribute:** ``/config/gpio-consumer/example
71
72 This is a group describing a single GPIO in th
73
74 For virtual consumers created using configfs w
75 this group can be considered as a mapping betw
76 of a single entry in ``'struct gpiod_lookup'``
77
78 The ``'key'`` attribute represents either the
79 belongs to or the GPIO line name. This depends
80 attribute: if its value is >= 0, then ``'key'`
81 chip to lookup while ``'offset'`` represents t
82 chip. If ``'offset'`` is < 0, then ``'key'`` r
83
84 The remaining attributes map to the ``'flags'`
85 struct. The first two take string values as ar
86
87 **``'drive'``:** ``'push-pull'``, ``'open-drai
88 **``'pull'``:** ``'pull-up'``, ``'pull-down'``
89
90 ``'active_low'`` and ``'transitory'`` are bool
91
92 Activating GPIO consumers
93 -------------------------
94
95 Once the confiuration is complete, the ``'live
96 order to instantiate the consumer. It can be s
97 virtual device. The module will synchronously
98 to be successfully probed and if this doesn't
99 result in an error.
100
101 Device-tree
102 -----------
103
104 Virtual GPIO consumers can also be defined in
105 must be: ``"gpio-virtuser"`` with at least one
106 standardized GPIO pattern.
107
108 An example device-tree code defining a virtual
109
110 .. code-block :: none
111
112 gpio-virt-consumer {
113 compatible = "gpio-virtuser";
114
115 foo-gpios = <&gpio0 5 GPIO_ACTIVE_LOW>
116 bar-gpios = <&gpio0 6 0>;
117 };
118
119 Controlling virtual GPIO consumers
120 ----------------------------------
121
122 Once active, the device will export debugfs at
123 arrays as well as each requested GPIO line sep
124 following device property: ``foo-gpios = <&gpi
125
126 The following debugfs attribute groups will be
127
128 **Group:** ``/sys/kernel/debug/gpio-virtuser/$
129
130 This is the group that will contain the attrib
131
132 **Attribute:** ``/sys/kernel/debug/gpio-virtus
133
134 **Attribute:** ``/sys/kernel/debug/gpio-virtus
135
136 Both attributes allow to read and set arrays o
137 exactly the number of values that the array co
138 containing zeroes and ones representing inacti
139 respectively. In this example: ``echo 11 > val
140
141 The ``values_atomic`` attribute works the same
142 will execute the GPIO driver callbacks in inte
143
144 **Group:** ``/sys/kernel/debug/gpio-virtuser/$
145
146 This is a group that represents a single GPIO
147 in the array.
148
149 **Attribute:** ``/sys/kernel/debug/gpio-virtus
150
151 Allows to set and read the consumer label of t
152
153 **Attribute:** ``/sys/kernel/debug/gpio-virtus
154
155 Allows to set and read the debounce period of
156
157 **Attribute:** ``/sys/kernel/debug/gpio-virtus
158
159 **Attribute:** ``/sys/kernel/debug/gpio-virtus
160
161 These two attributes allow to set the directio
162 "input" and "output" as values. The atomic var
163 in interrupt context.
164
165 **Attribute:** ``/sys/kernel/debug/gpio-virtus
166
167 If the line is requested in input mode, writin
168 make the module listen for edge interrupts on
169 the monitoring. Reading this attribute returns
170 interrupts (both edges).
171
172 **Attribute:** ``/sys/kernel/debug/gpio-virtus
173
174 **Attribute:** ``/sys/kernel/debug/gpio-virtus
175
176 Both attributes allow to read and set values o
177 They accept the following values: ``1`` and ``
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