Linux kernel Gpio Port programming entry __ Block chain

1. API interface

Request Gpio Port

int gpio_request (unsigned gpio, const char *label) free Gpio port

void Gpio_free (unsigned gpio)
Determine if the GPIO index number is valid (Gpio port exists)

int gpio_is_valid (int number);

Set Output: int gpio_direction_output (unsigned gpio, int value)

Set Input:

int gpio_direction_input (unsigned gpio)

Converts the Gpio port to the corresponding interrupt number

int Gpio_to_irq (unsigned gpio);

Interrupt Request REQUEST_IRQ


2. Code path:
2.1 DRIVERS/GPIO/GPIOLIB.C

3. Debugging Gpio Port

Perform:

echo >/sys/class/gpio/export

Subdirectories are generated under the/sys/class/gpio directory: gpio100, which has the following files:

Active_low direction
Power
Subsystem
Uevent
Value


cd/sys/class/gpio/gpio100

Gpio Port set to output: Echo out > Direction

Output High Level: Echo 1 > Value

Output low Level: Echo 0 > value

In addition, there is a LUA kernel porting project that already contains the read and write capabilities of the Gpio port, and the code path is as follows:

Https://github.com/negtise/luak-arm

Use the method to see the HowTo.txt in the Code root directory

In addition, you can view the information of the Gpio port through Cat/sys/kernel/debug/gpio.

4. Reference Documentation:
Linux/documentation/gpio.txt