diff options
Diffstat (limited to 'Documentation/driver-api/gpio/drivers-on-gpio.rst')
| -rw-r--r-- | Documentation/driver-api/gpio/drivers-on-gpio.rst | 28 |
1 files changed, 23 insertions, 5 deletions
diff --git a/Documentation/driver-api/gpio/drivers-on-gpio.rst b/Documentation/driver-api/gpio/drivers-on-gpio.rst index f3a189320e11..95572d2a94ce 100644 --- a/Documentation/driver-api/gpio/drivers-on-gpio.rst +++ b/Documentation/driver-api/gpio/drivers-on-gpio.rst @@ -27,7 +27,12 @@ hardware descriptions such as device tree or ACPI: 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. + an external speaker connected to a GPIO line. (If the beep is controlled by + off/on, for an actual PWM waveform, see pwm-gpio below.) + +- pwm-gpio: drivers/pwm/pwm-gpio.c is used to toggle a GPIO with a high + resolution timer producing a PWM waveform on the GPIO line, as well as + Linux high resolution timers can do. - 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 @@ -89,13 +94,26 @@ hardware descriptions such as device tree or ACPI: Consumer Electronics Control bus using only GPIO. It is used to communicate with devices on the HDMI bus. +- gpio-charger: drivers/power/supply/gpio-charger.c is used if you need to do + battery charging and all you have to go by to check the presence of the + AC charger or more complex tasks such as indicating charging status using + nothing but GPIO lines, this driver provides that and also a clearly defined + way to pass the charging parameters from hardware descriptions such as the + device tree. + +- gpio-mux: drivers/mux/gpio.c is used for controlling a multiplexer using + n GPIO lines such that you can mux in 2^n different devices by activating + different GPIO lines. Often the GPIOs are on a SoC and the devices are + some SoC-external entities, such as different components on a PCB that + can be selectively enabled. + 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. +Use those instead of talking directly to the GPIOs from userspace; 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. |