Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.
1 Subsystem drivers using GPIO 2 ============================ 3 4 Note that standard kernel drivers exist for common GPIO tasks and will provide 5 the right in-kernel and userspace APIs/ABIs for the job, and that these 6 drivers can quite easily interconnect with other kernel subsystems using 7 hardware descriptions such as device tree or ACPI: 8 9 - leds-gpio: drivers/leds/leds-gpio.c will handle LEDs connected to GPIO 10 lines, giving you the LED sysfs interface 11 12 - ledtrig-gpio: drivers/leds/trigger/ledtrig-gpio.c will provide a LED trigger, 13 i.e. a LED will turn on/off in response to a GPIO line going high or low 14 (and that LED may in turn use the leds-gpio as per above). 15 16 - gpio-keys: drivers/input/keyboard/gpio_keys.c is used when your GPIO line 17 can generate interrupts in response to a key press. Also supports debounce. 18 19 - gpio-keys-polled: drivers/input/keyboard/gpio_keys_polled.c is used when your 20 GPIO line cannot generate interrupts, so it needs to be periodically polled 21 by a timer. 22 23 - gpio_mouse: drivers/input/mouse/gpio_mouse.c is used to provide a mouse with 24 up to three buttons by simply using GPIOs and no mouse port. You can cut the 25 mouse cable and connect the wires to GPIO lines or solder a mouse connector 26 to the lines for a more permanent solution of this type. 27 28 - gpio-beeper: drivers/input/misc/gpio-beeper.c is used to provide a beep from 29 an external speaker connected to a GPIO line. 30 31 - extcon-gpio: drivers/extcon/extcon-gpio.c is used when you need to read an 32 external connector status, such as a headset line for an audio driver or an 33 HDMI connector. It will provide a better userspace sysfs interface than GPIO. 34 35 - restart-gpio: drivers/power/reset/gpio-restart.c is used to restart/reboot 36 the system by pulling a GPIO line and will register a restart handler so 37 userspace can issue the right system call to restart the system. 38 39 - poweroff-gpio: drivers/power/reset/gpio-poweroff.c is used to power the 40 system down by pulling a GPIO line and will register a pm_power_off() 41 callback so that userspace can issue the right system call to power down the 42 system. 43 44 - gpio-gate-clock: drivers/clk/clk-gpio.c is used to control a gated clock 45 (off/on) that uses a GPIO, and integrated with the clock subsystem. 46 47 - i2c-gpio: drivers/i2c/busses/i2c-gpio.c is used to drive an I2C bus 48 (two wires, SDA and SCL lines) by hammering (bitbang) two GPIO lines. It will 49 appear as any other I2C bus to the system and makes it possible to connect 50 drivers for the I2C devices on the bus like any other I2C bus driver. 51 52 - spi_gpio: drivers/spi/spi-gpio.c is used to drive an SPI bus (variable number 53 of wires, at least SCK and optionally MISO, MOSI and chip select lines) using 54 GPIO hammering (bitbang). It will appear as any other SPI bus on the system 55 and makes it possible to connect drivers for SPI devices on the bus like 56 any other SPI bus driver. For example any MMC/SD card can then be connected 57 to this SPI by using the mmc_spi host from the MMC/SD card subsystem. 58 59 - w1-gpio: drivers/w1/masters/w1-gpio.c is used to drive a one-wire bus using 60 a GPIO line, integrating with the W1 subsystem and handling devices on 61 the bus like any other W1 device. 62 63 - gpio-fan: drivers/hwmon/gpio-fan.c is used to control a fan for cooling the 64 system, connected to a GPIO line (and optionally a GPIO alarm line), 65 presenting all the right in-kernel and sysfs interfaces to make your system 66 not overheat. 67 68 - gpio-regulator: drivers/regulator/gpio-regulator.c is used to control a 69 regulator providing a certain voltage by pulling a GPIO line, integrating 70 with the regulator subsystem and giving you all the right interfaces. 71 72 - gpio-wdt: drivers/watchdog/gpio_wdt.c is used to provide a watchdog timer 73 that will periodically "ping" a hardware connected to a GPIO line by toggling 74 it from 1-to-0-to-1. If that hardware does not receive its "ping" 75 periodically, it will reset the system. 76 77 - gpio-nand: drivers/mtd/nand/gpio.c is used to connect a NAND flash chip to 78 a set of simple GPIO lines: RDY, NCE, ALE, CLE, NWP. It interacts with the 79 NAND flash MTD subsystem and provides chip access and partition parsing like 80 any other NAND driving hardware. 81 82 - ps2-gpio: drivers/input/serio/ps2-gpio.c is used to drive a PS/2 (IBM) serio 83 bus, data and clock line, by bit banging two GPIO lines. It will appear as 84 any other serio bus to the system and makes it possible to connect drivers 85 for e.g. keyboards and other PS/2 protocol based devices. 86 87 Apart from this there are special GPIO drivers in subsystems like MMC/SD to 88 read card detect and write protect GPIO lines, and in the TTY serial subsystem 89 to emulate MCTRL (modem control) signals CTS/RTS by using two GPIO lines. The 90 MTD NOR flash has add-ons for extra GPIO lines too, though the address bus is 91 usually connected directly to the flash. 92 93 Use those instead of talking directly to the GPIOs using sysfs; they integrate 94 with kernel frameworks better than your userspace code could. Needless to say, 95 just using the appropriate kernel drivers will simplify and speed up your 96 embedded hacking in particular by providing ready-made components.