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Diffstat (limited to 'Documentation/gpio/drivers-on-gpio.txt')
| -rw-r--r-- | Documentation/gpio/drivers-on-gpio.txt | 96 |
1 files changed, 0 insertions, 96 deletions
diff --git a/Documentation/gpio/drivers-on-gpio.txt b/Documentation/gpio/drivers-on-gpio.txt deleted file mode 100644 index a2ccbab12eb7..000000000000 --- a/Documentation/gpio/drivers-on-gpio.txt +++ /dev/null @@ -1,96 +0,0 @@ -Subsystem drivers using GPIO -============================ - -Note that standard kernel drivers exist for common GPIO tasks and will provide -the right in-kernel and userspace APIs/ABIs for the job, and that these -drivers can quite easily interconnect with other kernel subsystems using -hardware descriptions such as device tree or ACPI: - -- leds-gpio: drivers/leds/leds-gpio.c will handle LEDs connected to GPIO - lines, giving you the LED sysfs interface - -- ledtrig-gpio: drivers/leds/trigger/ledtrig-gpio.c will provide a LED trigger, - i.e. a LED will turn on/off in response to a GPIO line going high or low - (and that LED may in turn use the leds-gpio as per above). - -- gpio-keys: drivers/input/keyboard/gpio_keys.c is used when your GPIO line - can generate interrupts in response to a key press. Also supports debounce. - -- gpio-keys-polled: drivers/input/keyboard/gpio_keys_polled.c is used when your - GPIO line cannot generate interrupts, so it needs to be periodically polled - by a timer. - -- gpio_mouse: drivers/input/mouse/gpio_mouse.c is used to provide a mouse with - up to three buttons by simply using GPIOs and no mouse port. You can cut the - mouse cable and connect the wires to GPIO lines or solder a mouse connector - to the lines for a more permanent solution of this type. - -- gpio-beeper: drivers/input/misc/gpio-beeper.c is used to provide a beep from - an external speaker connected to a GPIO line. - -- extcon-gpio: drivers/extcon/extcon-gpio.c is used when you need to read an - external connector status, such as a headset line for an audio driver or an - HDMI connector. It will provide a better userspace sysfs interface than GPIO. - -- restart-gpio: drivers/power/reset/gpio-restart.c is used to restart/reboot - the system by pulling a GPIO line and will register a restart handler so - userspace can issue the right system call to restart the system. - -- poweroff-gpio: drivers/power/reset/gpio-poweroff.c is used to power the - system down by pulling a GPIO line and will register a pm_power_off() - callback so that userspace can issue the right system call to power down the - system. - -- gpio-gate-clock: drivers/clk/clk-gpio.c is used to control a gated clock - (off/on) that uses a GPIO, and integrated with the clock subsystem. - -- i2c-gpio: drivers/i2c/busses/i2c-gpio.c is used to drive an I2C bus - (two wires, SDA and SCL lines) by hammering (bitbang) two GPIO lines. It will - appear as any other I2C bus to the system and makes it possible to connect - drivers for the I2C devices on the bus like any other I2C bus driver. - -- spi_gpio: drivers/spi/spi-gpio.c is used to drive an SPI bus (variable number - of wires, at least SCK and optionally MISO, MOSI and chip select lines) using - GPIO hammering (bitbang). It will appear as any other SPI bus on the system - and makes it possible to connect drivers for SPI devices on the bus like - any other SPI bus driver. For example any MMC/SD card can then be connected - to this SPI by using the mmc_spi host from the MMC/SD card subsystem. - -- w1-gpio: drivers/w1/masters/w1-gpio.c is used to drive a one-wire bus using - a GPIO line, integrating with the W1 subsystem and handling devices on - the bus like any other W1 device. - -- gpio-fan: drivers/hwmon/gpio-fan.c is used to control a fan for cooling the - system, connected to a GPIO line (and optionally a GPIO alarm line), - presenting all the right in-kernel and sysfs interfaces to make your system - not overheat. - -- gpio-regulator: drivers/regulator/gpio-regulator.c is used to control a - regulator providing a certain voltage by pulling a GPIO line, integrating - with the regulator subsystem and giving you all the right interfaces. - -- gpio-wdt: drivers/watchdog/gpio_wdt.c is used to provide a watchdog timer - that will periodically "ping" a hardware connected to a GPIO line by toggling - it from 1-to-0-to-1. If that hardware does not receive its "ping" - periodically, it will reset the system. - -- gpio-nand: drivers/mtd/nand/gpio.c is used to connect a NAND flash chip to - a set of simple GPIO lines: RDY, NCE, ALE, CLE, NWP. It interacts with the - NAND flash MTD subsystem and provides chip access and partition parsing like - any other NAND driving hardware. - -- ps2-gpio: drivers/input/serio/ps2-gpio.c is used to drive a PS/2 (IBM) serio - bus, data and clock line, by bit banging two GPIO lines. It will appear as - any other serio bus to the system and makes it possible to connect drivers - for e.g. keyboards and other PS/2 protocol based devices. - -Apart from this there are special GPIO drivers in subsystems like MMC/SD to -read card detect and write protect GPIO lines, and in the TTY serial subsystem -to emulate MCTRL (modem control) signals CTS/RTS by using two GPIO lines. The -MTD NOR flash has add-ons for extra GPIO lines too, though the address bus is -usually connected directly to the flash. - -Use those instead of talking directly to the GPIOs using sysfs; they integrate -with kernel frameworks better than your userspace code could. Needless to say, -just using the appropriate kernel drivers will simplify and speed up your -embedded hacking in particular by providing ready-made components. |