Linux应用程序——用户层操作GPIO

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我是靠谱客的博主直率电灯胆，最近开发中收集的这篇文章主要介绍Linux应用程序——用户层操作GPIO，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

Linux应用程序——用户层操作GPIO_放羊娃的博客-CSDN博客_linux 操作gpio

stm32mp157 盘古开发板 Linux内核版本4.19

1、拜兔核i2SOM的wiki上关于gpio应用的说明

2、gpio操作相关的数据结构

3、测试代码：

4、参考链接

1、拜兔核i2SOM的wiki上关于gpio应用的说明
链接：http://wiki.i2som.com/pages/viewpage.action?pageId=22479311

以下是链接中的复制内容：

GPIO操作在Linux系统上是常用功能，STM32MP1芯片平台也同样支持。从Linux 4.8版本开始，Linux引入了新的gpio操作方式，GPIO字符设备。不再使用以前SYSFS方式在"/sys/class/gpio"目录下来操作GPIO，而是，基于"文件描述符"的字符设备，每个GPIO组在"/dev"下有一个对应的gpiochip文件，例如"/dev/gpiochip0, /dev/gpiochip1"。使用常规的LInux文件操作方式即可操作这些gpiochip文件，基本可以概括为open() + ioctl() + poll() + read() + close()。

STM32MP1平台的gpiochip文件描述

字符设备

描述

/dev/gpiochip0   GPIOA
/dev/gpiochip1   GPIOB
/dev/gpiochip2   GPIOC
/dev/gpiochip3   GPIOD
/dev/gpiochip4   GPIOE
/dev/gpiochip5   GPIOF
/dev/gpiochip6   GPIOG
/dev/gpiochip7   GPIOH
/dev/gpiochip8   GPIOI
/dev/gpiochip9   GPIOJ
/dev/gpiochip10   GPIOK
/dev/gpiochip11   GPIOZ
gpiochip 操作

gpio申请

flags: desired flags for the desired GPIO lines, such as GPIOHANDLE_REQUEST_OUTPUT, GPIOHANDLE_REQUEST_ACTIVE_LOW etc, OR:ed * together. Note that even if multiple lines are requested, the same flags * must be applicable to all of them, if you want lines with individual * flags set, request them one by one. It is possible to select * a batch of input or output lines, but they must all have the same * characteristics, i.e. all inputs or all outputs, all active low etc

lines: number of lines requested in this request, i.e. the number of valid fields in the above arrays, set to 1 to request a single line

struct gpiohandle_request {

__u32 lineoffsets[GPIOHANDLES_MAX];

__u32 flags;

__u8 default_values[GPIOHANDLES_MAX];

char consumer_label[32];

__u32 lines;

int fd;

};

#define GPIOHANDLES_MAX 64

#define GPIOHANDLE_REQUEST_INPUT (1UL << 0)

#define GPIOHANDLE_REQUEST_OUTPUT (1UL << 1)

#define GPIOHANDLE_REQUEST_ACTIVE_LOW (1UL << 2)

#define GPIOHANDLE_REQUEST_OPEN_DRAIN (1UL << 3)

#define GPIOHANDLE_REQUEST_OPEN_SOURCE (1UL << 4)

gpio 操作数据

struct gpiohandle_data {

__u8 values[GPIOHANDLES_MAX];

};

gpio event的申请

handleflags: desired handle flags for the desired GPIO line, such as GPIOHANDLE_REQUEST_ACTIVE_LOW or GPIOHANDLE_REQUEST_OPEN_DRAIN

eventflags: desired flags for the desired GPIO event line, such as GPIOEVENT_REQUEST_RISING_EDGE or GPIOEVENT_REQUEST_FALLING_EDGE

struct gpioevent_request {

__u32 lineoffset;

__u32 handleflags;

__u32 eventflags;

char consumer_label[32];

int fd;

};

#define GPIOEVENT_REQUEST_RISING_EDGE (1UL << 0)

#define GPIOEVENT_REQUEST_FALLING_EDGE (1UL << 1)

#define GPIOEVENT_REQUEST_BOTH_EDGES ((1UL << 0) | (1UL << 1))

gpio event

struct gpioevent_data {

__u64 timestamp;

__u32 id;

};

#define GPIOEVENT_EVENT_RISING_EDGE 0x01

#define GPIOEVENT_EVENT_FALLING_EDGE 0x02

以下是使用C语言操作PZ0管脚的示例代码。

#include <errno.h>

#include <fcntl.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <sys/ioctl.h>

#include <unistd.h>

#include <linux/gpio.h>

int main(int argc, char **argv)

{

struct gpiohandle_request req;

struct gpiohandle_data data;

char chrdev_name[20];

int fd, ret;

strcpy(chrdev_name, "/dev/gpiochip11");

/* Open device: gpiochip11 for GPIO bank Z */

fd = open(chrdev_name, 0);

if (fd == -1) {

ret = -errno;

fprintf(stderr, "Failed to open %sn", chrdev_name);

return ret;

}

/* request GPIO line: GPIO_Z_0 */

req.lineoffsets[0] = 0;

req.flags = GPIOHANDLE_REQUEST_OUTPUT;

memcpy(req.default_values, &data, sizeof(req.default_values));

strcpy(req.consumer_label, "led_gpio_z_0");

req.lines = 1;

ret = ioctl(fd, GPIO_GET_LINEHANDLE_IOCTL, &req);

if (ret == -1) {

ret = -errno;

fprintf(stderr, "Failed to issue GET LINEHANDLE IOCTL (%d)n",

ret);

}

if (close(fd) == -1)

perror("Failed to close GPIO character device file");

/* Start led blinking */

while(1) {

data.values[0] = !data.values[0];

ret = ioctl(req.fd, GPIOHANDLE_SET_LINE_VALUES_IOCTL, &data);

if (ret == -1) {

ret = -errno;

fprintf(stderr, "Failed to issue %s (%d)n",

"GPIOHANDLE_SET_LINE_VALUES_IOCTL", ret);

}

sleep(1);

}

/* release line */

ret = close(req.fd);

if (ret == -1) {

perror("Failed to close GPIO LINEHANDLE device file");

ret = -errno;

}

return ret;

}

将以上代码保存为gpio.c文件，然后加载SDK环境变量后，就可以编译了。

$CC gpio.c -o gpio

编译后的gpio文件，可以拷贝到开发板上运行。

Libgpiod

由于gpiochip的方式，基于C语言，所以开发者实现了Libgpiod，提供了一些工具和更简易的C API接口。

Libgpiod (Library General Purpose Input/Output device) 提供了完整的API 给开发者，同时还提供了一些用户空间下的应用来操作GPIO。

gpiodetect – list all gpiochips present on the system, their names, labels and number of GPIO lines
gpioinfo – list all lines of specified gpiochips, their names, consumers, direction, active state and additional flags
gpioget – read values of specified GPIO lines
gpioset – set values of specified GPIO lines, potentially keep the lines exported and wait until timeout, user input or signal
gpiofind – find the gpiochip name and line offset given the line name
gpiomon – wait for events on GPIO lines, specify which events to watch, how many events to process before exiting or if the events should be reported to the console
仓库地址 https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/

API https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/tree/include/gpiod.h

libgpiod introduction video: https://www.youtube.com/watch?v=76j3TIqTPTI

2、gpio操作相关的数据结构
内核目录：linux-stincludeuapilinuxgpio.h

/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
/*
* <linux/gpio.h> - userspace ABI for the GPIO character devices
*
* Copyright (C) 2016 Linus Walleij
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 as published by
* the Free Software Foundation.
*/
#ifndef _UAPI_GPIO_H_
#define _UAPI_GPIO_H_

#include <linux/ioctl.h>
#include <linux/types.h>

/**
* struct gpiochip_info - Information about a certain GPIO chip
* @name: the Linux kernel name of this GPIO chip
* @label: a functional name for this GPIO chip, such as a product
* number, may be NULL
* @lines: number of GPIO lines on this chip
*/
struct gpiochip_info {
   char name[32];
   char label[32];
   __u32 lines;
};

/* Informational flags */
#define GPIOLINE_FLAG_KERNEL       (1UL << 0) /* Line used by the kernel */
#define GPIOLINE_FLAG_IS_OUT       (1UL << 1)
#define GPIOLINE_FLAG_ACTIVE_LOW   (1UL << 2)
#define GPIOLINE_FLAG_OPEN_DRAIN   (1UL << 3)
#define GPIOLINE_FLAG_OPEN_SOURCE   (1UL << 4)

/**
* struct gpioline_info - Information about a certain GPIO line
* @line_offset: the local offset on this GPIO device, fill this in when
* requesting the line information from the kernel
* @flags: various flags for this line
* @name: the name of this GPIO line, such as the output pin of the line on the
* chip, a rail or a pin header name on a board, as specified by the gpio
* chip, may be NULL
* @consumer: a functional name for the consumer of this GPIO line as set by
* whatever is using it, will be NULL if there is no current user but may
* also be NULL if the consumer doesn't set this up
*/
struct gpioline_info {
   __u32 line_offset;
   __u32 flags;
   char name[32];
   char consumer[32];
};

/* Maximum number of requested handles */
#define GPIOHANDLES_MAX 64

/* Linerequest flags */
#define GPIOHANDLE_REQUEST_INPUT   (1UL << 0)
#define GPIOHANDLE_REQUEST_OUTPUT   (1UL << 1)
#define GPIOHANDLE_REQUEST_ACTIVE_LOW   (1UL << 2)
#define GPIOHANDLE_REQUEST_OPEN_DRAIN   (1UL << 3)
#define GPIOHANDLE_REQUEST_OPEN_SOURCE   (1UL << 4)

/**
* struct gpiohandle_request - Information about a GPIO handle request
* @lineoffsets: an array desired lines, specified by offset index for the
* associated GPIO device
* @flags: desired flags for the desired GPIO lines, such as
* GPIOHANDLE_REQUEST_OUTPUT, GPIOHANDLE_REQUEST_ACTIVE_LOW etc, OR:ed
* together. Note that even if multiple lines are requested, the same flags
* must be applicable to all of them, if you want lines with individual
* flags set, request them one by one. It is possible to select
* a batch of input or output lines, but they must all have the same
* characteristics, i.e. all inputs or all outputs, all active low etc
* @default_values: if the GPIOHANDLE_REQUEST_OUTPUT is set for a requested
* line, this specifies the default output value, should be 0 (low) or
* 1 (high), anything else than 0 or 1 will be interpreted as 1 (high)
* @consumer_label: a desired consumer label for the selected GPIO line(s)
* such as "my-bitbanged-relay"
* @lines: number of lines requested in this request, i.e. the number of
* valid fields in the above arrays, set to 1 to request a single line
* @fd: if successful this field will contain a valid anonymous file handle
* after a GPIO_GET_LINEHANDLE_IOCTL operation, zero or negative value
* means error
*/
struct gpiohandle_request {
   __u32 lineoffsets[GPIOHANDLES_MAX];
   __u32 flags;
   __u8 default_values[GPIOHANDLES_MAX];
   char consumer_label[32];
   __u32 lines;
   int fd;
};

/**
* struct gpiohandle_data - Information of values on a GPIO handle
* @values: when getting the state of lines this contains the current
* state of a line, when setting the state of lines these should contain
* the desired target state
*/
struct gpiohandle_data {
   __u8 values[GPIOHANDLES_MAX];
};

#define GPIOHANDLE_GET_LINE_VALUES_IOCTL _IOWR(0xB4, 0x08, struct gpiohandle_data)
#define GPIOHANDLE_SET_LINE_VALUES_IOCTL _IOWR(0xB4, 0x09, struct gpiohandle_data)

/* Eventrequest flags */
#define GPIOEVENT_REQUEST_RISING_EDGE   (1UL << 0)
#define GPIOEVENT_REQUEST_FALLING_EDGE   (1UL << 1)
#define GPIOEVENT_REQUEST_BOTH_EDGES   ((1UL << 0) | (1UL << 1))

/**
* struct gpioevent_request - Information about a GPIO event request
* @lineoffset: the desired line to subscribe to events from, specified by
* offset index for the associated GPIO device
* @handleflags: desired handle flags for the desired GPIO line, such as
* GPIOHANDLE_REQUEST_ACTIVE_LOW or GPIOHANDLE_REQUEST_OPEN_DRAIN
* @eventflags: desired flags for the desired GPIO event line, such as
* GPIOEVENT_REQUEST_RISING_EDGE or GPIOEVENT_REQUEST_FALLING_EDGE
* @consumer_label: a desired consumer label for the selected GPIO line(s)
* such as "my-listener"
* @fd: if successful this field will contain a valid anonymous file handle
* after a GPIO_GET_LINEEVENT_IOCTL operation, zero or negative value
* means error
*/
struct gpioevent_request {
   __u32 lineoffset;
   __u32 handleflags;
   __u32 eventflags;
   char consumer_label[32];
   int fd;
};

/**
* GPIO event types
*/
#define GPIOEVENT_EVENT_RISING_EDGE 0x01
#define GPIOEVENT_EVENT_FALLING_EDGE 0x02

/**
* struct gpioevent_data - The actual event being pushed to userspace
* @timestamp: best estimate of time of event occurrence, in nanoseconds
* @id: event identifier
*/
struct gpioevent_data {
   __u64 timestamp;   // 应该是以纳秒为单位的时间戳
   __u32 id;
};

#define GPIO_GET_CHIPINFO_IOCTL _IOR(0xB4, 0x01, struct gpiochip_info)
#define GPIO_GET_LINEINFO_IOCTL _IOWR(0xB4, 0x02, struct gpioline_info)
#define GPIO_GET_LINEHANDLE_IOCTL _IOWR(0xB4, 0x03, struct gpiohandle_request)
#define GPIO_GET_LINEEVENT_IOCTL _IOWR(0xB4, 0x04, struct gpioevent_request)

#endif /* _UAPI_GPIO_H_ *
3、测试代码：
该测试代码位于

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/poll.h>
#include <unistd.h>

#include <linux/gpio.h>

int main(int argc, char **argv)
{
   struct gpiohandle_request req;
   struct gpiohandle_data data;
   char chrdev_name[20];
   int fd, ret;

   struct gpiochip_info chip_info;
   struct gpioline_info line_info;
   struct gpioevent_request event_req;
   struct gpioevent_data event_data;
   /*
   poll函数原型：
   int poll(struct pollfd *fds, nfds_t nfds, int timeout);
   struct pollfd {
       int fd; // file descriptor
       short events; // requested events
       short revents; // returned events
   };
   fd是要查询的设备，events是期望获得的事件，这里我们将他设置为：POLLIN
   fds定义一个数组，存放需要poll的所有设备。poll操作会同时查询这些设备。
   nfds为查询的文件数量
   timeout为超时时间
   */
   struct pollfd poll_fd;

   //如果不知道gpiochipN对应的是GPIO?，可以查看/sys/bus/gpio/devices/gpiochip0/of_node# cat st,bank-name 输出结果是GPIOA
   strcpy(chrdev_name, "/dev/gpiochip11");

   /* Open device: gpiochip11 for GPIO bank Z */
   fd = open(chrdev_name, 0);
   if (fd == -1) {
       ret = -errno;
       fprintf(stderr, "Failed to open %sn", chrdev_name);

       return ret;
   }

   /*
   获取gpio chip info，即打开的设备文件"/dev/gpiochip11"的chipinfo
   */
   if ((ret = ioctl(fd, GPIO_GET_CHIPINFO_IOCTL, &chip_info)) < 0){
printf("GPIO_GET_CHIPINFO_IOCTL failedn");
return -errno;
}
printf("chip_info.name = %s, chip_info.label = %s, chip_info.lines = %dn",
           chip_info.name, chip_info.label, chip_info.lines);

   /*
   获取gpio line info, 即获取chip"/dev/gpiochip11"里面第0个引脚的info，即pz0的info
   */
   line_info.line_offset = 0;
if ((ret = ioctl(fd, GPIO_GET_LINEINFO_IOCTL, &line_info)) < 0){
printf("GPIO_GET_LINEINFO_IOCTL failedn");
return -errno;
}
printf("line_info.line_offset = %d, line_info.flags = %d, line_info.name = %s, line_info.consumer = %sn", line_info.line_offset, line_info.flags, line_info.name, line_info.consumer);

   /* handle request GPIO line: GPIO_Z_0 */
   req.lineoffsets[0] = 0;
   req.flags = GPIOHANDLE_REQUEST_OUTPUT;
   memcpy(req.default_values, &data, sizeof(req.default_values));
   strcpy(req.consumer_label, "led_gpio_z_0");
   req.lines = 1;

   /* event request */
   event_req.lineoffset = 0;
   event_req.handleflags = GPIOHANDLE_REQUEST_INPUT;
   event_req.eventflags = GPIOEVENT_REQUEST_RISING_EDGE;

   //ret = ioctl(fd, GPIO_GET_LINEHANDLE_IOCTL, &req);   // handle测试的时候用这个
   ret = ioctl(fd, GPIO_GET_LINEEVENT_IOCTL, &event_req);   // event测试的时候用这个
   if (ret == -1) {
       ret = -errno;
       fprintf(stderr, "Failed to issue GET LINEHANDLE IOCTL (%d)n", ret);
   }
   if (close(fd) == -1)
       perror("Failed to close GPIO character device file");

   poll_fd.fd = event_req.fd;   //注意这个event_req.fd是ret = ioctl(fd, GPIO_GET_LINEEVENT_IOCTL, &event_req);返回的
   poll_fd.events = POLLIN;

   while(1) {
       /* handle测试，即设置IO口输出高低电平
       data.values[0] = !data.values[0];
       ret = ioctl(req.fd, GPIOHANDLE_SET_LINE_VALUES_IOCTL, &data);
       if (ret == -1) {
           ret = -errno;
           fprintf(stderr, "Failed to issue %s (%d)n", "GPIOHANDLE_SET_LINE_VALUES_IOCTL", ret);
       }
       sleep(1);
       */

       /* event测试，即监控IO输入电平的高低，触发事件的方式有上升沿触发、下降沿触发等 */
       ret = poll(&poll_fd, 1, 3000);
       if(ret == 0)
           printf("time out n");
       else{
           printf("revents:%d n", poll_fd.revents);
           event_data.timestamp = 0;
           event_data.id = 0;
           // 这里一定要将中断的事件读出来，否则会一直处于触发状态
           read(event_req.fd, &event_data, sizeof(event_data));
           // event_data.timestamp是以纳秒为单位的时间戳
           printf("event_data.timestamp:%llu, event_data.id:%d n", event_data.timestamp, event_data.id);
       }
   }

   /* release line */
   ret = close(req.fd);
   if (ret == -1) {
       perror("Failed to close GPIO LINEHANDLE device file");
       ret = -errno;
   }
   return ret;
}
对这里面的poll的使用还不是很清楚

4、参考链接
http://blog.chinaunix.net/uid-9672747-id-5788440.html

http://www.voidcn.com/article/p-uaoezkpv-bau.html

http://www.voidcn.com/article/p-gmssshgp-xr.html

https://blog.csdn.net/djinglan/article/details/8302938

https://www.cnblogs.com/wen123456/p/14046890.html

http://blog.chinaunix.net/uid-31087949-id-5793457.html
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版权声明：本文为CSDN博主「放羊娃」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/fang_yang_wa/article/details/113572733