1 .. SPDX-License-Identifier: GPL-2.0-only 1 .. SPDX-License-Identifier: GPL-2.0-only
2 2
3 GPIO Testing Driver 3 GPIO Testing Driver
4 =================== 4 ===================
5 5
6 .. note:: <<
7 <<
8 This module has been obsoleted by the more <<
9 New developments should use that API and ex <<
10 encouraged to migrate as soon as possible. <<
11 This module will continue to be maintained <<
12 added. <<
13 <<
14 The GPIO Testing Driver (gpio-mockup) provides 6 The GPIO Testing Driver (gpio-mockup) provides a way to create simulated GPIO
15 chips for testing purposes. The lines exposed 7 chips for testing purposes. The lines exposed by these chips can be accessed
16 using the standard GPIO character device inter 8 using the standard GPIO character device interface as well as manipulated
17 using the dedicated debugfs directory structur 9 using the dedicated debugfs directory structure.
18 10
19 Creating simulated chips using module params 11 Creating simulated chips using module params
20 -------------------------------------------- 12 --------------------------------------------
21 13
22 When loading the gpio-mockup driver a number o 14 When loading the gpio-mockup driver a number of parameters can be passed to the
23 module. 15 module.
24 16
25 gpio_mockup_ranges 17 gpio_mockup_ranges
26 18
27 This parameter takes an argument in th 19 This parameter takes an argument in the form of an array of integer
28 pairs. Each pair defines the base GPIO 20 pairs. Each pair defines the base GPIO number (non-negative integer)
29 and the first number after the last of 21 and the first number after the last of this chip. If the base GPIO
30 is -1, the gpiolib will assign it auto 22 is -1, the gpiolib will assign it automatically. while the following
31 parameter is the number of lines expos 23 parameter is the number of lines exposed by the chip.
32 24
33 Example: gpio_mockup_ranges=-1,8,-1,16 25 Example: gpio_mockup_ranges=-1,8,-1,16,405,409
34 26
35 The line above creates three chips. Th 27 The line above creates three chips. The first one will expose 8 lines,
36 the second 16 and the third 4. The bas 28 the second 16 and the third 4. The base GPIO for the third chip is set
37 to 405 while for two first chips it wi 29 to 405 while for two first chips it will be assigned automatically.
38 30
39 gpio_mockup_named_lines 31 gpio_mockup_named_lines
40 32
41 This parameter doesn't take any argume 33 This parameter doesn't take any arguments. It lets the driver know that
42 GPIO lines exposed by it should be nam 34 GPIO lines exposed by it should be named.
43 35
44 The name format is: gpio-mockup-X-Y wh 36 The name format is: gpio-mockup-X-Y where X is mockup chip's ID
45 and Y is the line offset. 37 and Y is the line offset.
46 38
47 Manipulating simulated lines 39 Manipulating simulated lines
48 ---------------------------- 40 ----------------------------
49 41
50 Each mockup chip creates its own subdirectory 42 Each mockup chip creates its own subdirectory in /sys/kernel/debug/gpio-mockup/.
51 The directory is named after the chip's label. 43 The directory is named after the chip's label. A symlink is also created, named
52 after the chip's name, which points to the lab 44 after the chip's name, which points to the label directory.
53 45
54 Inside each subdirectory, there's a separate a 46 Inside each subdirectory, there's a separate attribute for each GPIO line. The
55 name of the attribute represents the line's of 47 name of the attribute represents the line's offset in the chip.
56 48
57 Reading from a line attribute returns the curr 49 Reading from a line attribute returns the current value. Writing to it (0 or 1)
58 changes the configuration of the simulated pul 50 changes the configuration of the simulated pull-up/pull-down resistor
59 (1 - pull-up, 0 - pull-down). 51 (1 - pull-up, 0 - pull-down).
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