GNU/Linux - MenuConfig of Kernel: CONFIG_GPIOLIB + CONFIG_GPIO_SYSFS

In the Linux kernel configuration, CONFIG_GPIOLIB is an option that enables support for the GPIO (General Purpose Input/Output) library (gpiolib). This library provides a generic interface for managing GPIO pins, allowing drivers and user-space applications to interact with GPIOs in a uniform way, regardless of the underlying hardware architecture.

When CONFIG_GPIOLIB is enabled, the following functionalities become available:

1. GPIO Manipulation: The GPIO library provides functions for setting the direction of GPIO pins (input or output), reading and writing GPIO values, and controlling other GPIO-related features.

2. GPIO Event Handling: Applications can register to receive notifications when GPIO events occur, such as changes in input values (e.g., rising or falling edges). This is commonly used for tasks like button presses, sensor data acquisition, or interrupt handling.

3. GPIO Export and Unexport: GPIO pins can be dynamically exported and unexported to user space, allowing user-space applications to access and control GPIO pins without needing direct kernel access.

4. GPIO Chip Abstraction: The GPIO library abstracts hardware-specific details of GPIO controllers, allowing drivers and applications to work with GPIO pins in a platform-independent manner.

Enabling CONFIG_GPIOLIB in the kernel configuration allows developers to utilize GPIO pins for various purposes, including controlling hardware peripherals, interfacing with sensors, implementing user interfaces, and more, using standardized and easy-to-use interfaces provided by the kernel.

In the Linux kernel configuration, CONFIG_GPIO_SYSFS is an option that enables support for exporting GPIO pins to the Sysfs filesystem (/sys/class/gpio/).

The Sysfs filesystem is a virtual filesystem in Linux that provides an interface for interacting with kernel objects and subsystems. When CONFIG_GPIO_SYSFS is enabled, along with CONFIG_GPIOLIB, the GPIO pins are exposed as files in the Sysfs GPIO interface. This allows user-space applications to control GPIO pins by reading from and writing to these files.

Here's what CONFIG_GPIO_SYSFS enables:

1. GPIO Export: GPIO pins can be exported to user space, making them accessible through Sysfs. This allows applications to manipulate GPIO pins without needing direct kernel access.

2. Dynamic GPIO Allocation: GPIO pins can be dynamically allocated and deallocated by writing to files in the Sysfs GPIO interface. This is useful for systems where GPIO pins need to be allocated or released dynamically based on runtime conditions.

3. GPIO Direction and Value Control: GPIO pins can be configured as input or output and their values can be set or read by writing to or reading from files in the Sysfs GPIO interface.

4. Interrupt Handling: Some GPIO-related events, such as rising or falling edges, can be configured to trigger interrupts. The configuration of these interrupts can also be done through the Sysfs GPIO interface.

In summary, CONFIG_GPIO_SYSFS enables the GPIO Sysfs interface in the Linux kernel, providing a convenient way for user-space applications to interact with GPIO pins without needing direct kernel access or specific device drivers. This feature is commonly used for tasks such as controlling peripherals, interfacing with sensors, or implementing user interfaces.