1 ============================
2 Subsystem drivers using GPIO
3 ============================
4
5 Note that standard kernel drivers exist for co
6 the right in-kernel and userspace APIs/ABIs fo
7 drivers can quite easily interconnect with oth
8 hardware descriptions such as device tree or A
9
10 - leds-gpio: drivers/leds/leds-gpio.c will han
11 lines, giving you the LED sysfs interface
12
13 - ledtrig-gpio: drivers/leds/trigger/ledtrig-g
14 i.e. a LED will turn on/off in response to a
15 (and that LED may in turn use the leds-gpio
16
17 - gpio-keys: drivers/input/keyboard/gpio_keys.
18 can generate interrupts in response to a key
19
20 - gpio-keys-polled: drivers/input/keyboard/gpi
21 GPIO line cannot generate interrupts, so it
22 by a timer.
23
24 - gpio_mouse: drivers/input/mouse/gpio_mouse.c
25 up to three buttons by simply using GPIOs an
26 mouse cable and connect the wires to GPIO li
27 to the lines for a more permanent solution o
28
29 - gpio-beeper: drivers/input/misc/gpio-beeper.
30 an external speaker connected to a GPIO line
31 off/on, for an actual PWM waveform, see pwm-
32
33 - pwm-gpio: drivers/pwm/pwm-gpio.c is used to
34 resolution timer producing a PWM waveform on
35 Linux high resolution timers can do.
36
37 - extcon-gpio: drivers/extcon/extcon-gpio.c is
38 external connector status, such as a headset
39 HDMI connector. It will provide a better use
40
41 - restart-gpio: drivers/power/reset/gpio-resta
42 the system by pulling a GPIO line and will r
43 userspace can issue the right system call to
44
45 - poweroff-gpio: drivers/power/reset/gpio-powe
46 system down by pulling a GPIO line and will
47 callback so that userspace can issue the rig
48 system.
49
50 - gpio-gate-clock: drivers/clk/clk-gpio.c is u
51 (off/on) that uses a GPIO, and integrated wi
52
53 - i2c-gpio: drivers/i2c/busses/i2c-gpio.c is u
54 (two wires, SDA and SCL lines) by hammering
55 appear as any other I2C bus to the system an
56 drivers for the I2C devices on the bus like
57
58 - spi_gpio: drivers/spi/spi-gpio.c is used to
59 of wires, at least SCK and optionally MISO,
60 GPIO hammering (bitbang). It will appear as
61 and makes it possible to connect drivers for
62 any other SPI bus driver. For example any MM
63 to this SPI by using the mmc_spi host from t
64
65 - w1-gpio: drivers/w1/masters/w1-gpio.c is use
66 a GPIO line, integrating with the W1 subsyst
67 the bus like any other W1 device.
68
69 - gpio-fan: drivers/hwmon/gpio-fan.c is used t
70 system, connected to a GPIO line (and option
71 presenting all the right in-kernel and sysfs
72 not overheat.
73
74 - gpio-regulator: drivers/regulator/gpio-regul
75 regulator providing a certain voltage by pul
76 with the regulator subsystem and giving you
77
78 - gpio-wdt: drivers/watchdog/gpio_wdt.c is use
79 that will periodically "ping" a hardware con
80 it from 1-to-0-to-1. If that hardware does n
81 periodically, it will reset the system.
82
83 - gpio-nand: drivers/mtd/nand/raw/gpio.c is us
84 to a set of simple GPIO lines: RDY, NCE, ALE
85 NAND flash MTD subsystem and provides chip a
86 any other NAND driving hardware.
87
88 - ps2-gpio: drivers/input/serio/ps2-gpio.c is
89 bus, data and clock line, by bit banging two
90 any other serio bus to the system and makes
91 for e.g. keyboards and other PS/2 protocol b
92
93 - cec-gpio: drivers/media/platform/cec-gpio/ i
94 Consumer Electronics Control bus using only
95 with devices on the HDMI bus.
96
97 - gpio-charger: drivers/power/supply/gpio-char
98 battery charging and all you have to go by t
99 AC charger or more complex tasks such as ind
100 nothing but GPIO lines, this driver provides
101 way to pass the charging parameters from har
102 device tree.
103
104 - gpio-mux: drivers/mux/gpio.c is used for con
105 n GPIO lines such that you can mux in 2^n di
106 different GPIO lines. Often the GPIOs are on
107 some SoC-external entities, such as differen
108 can be selectively enabled.
109
110 Apart from this there are special GPIO drivers
111 read card detect and write protect GPIO lines,
112 to emulate MCTRL (modem control) signals CTS/R
113 MTD NOR flash has add-ons for extra GPIO lines
114 usually connected directly to the flash.
115
116 Use those instead of talking directly to the G
117 integrate with kernel frameworks better than y
118 Needless to say, just using the appropriate ke
119 speed up your embedded hacking in particular b
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