Linux学习笔记（15.4）——LED设备驱动之面向对象演进4（用设备树）

2022-03-15 12:06:34

Linux学习笔记（15.3）采用platform_device指定LED资源，即：

  • 首先，根据实际电路将LED的引脚信息（默认状态、打开时电平、GPIO时钟开关位偏移量、引脚序号、GPIO物理地址）初始化；
  • 然后，定义struct resource类型的led_res资源，将.start成员指向上面定义的LED引脚信息；
  • 接着，定义struct platform_device类型的led_dev资源，指定资源的名称.name、.num_resources(几个LED)、.resource(led_res)成员；
  • 最后，在led_dev的初始化函数中将struct platform_device类型的led_dev资源注册到平台设备，即platform_device_register(&led_dev)。
    那么，能否省去这个文件不要让具体板子资源挤占linux内核？设备树便应运而生。
  1. 本文，我们将实际电路的LED信息放在设备树的根节点（如下），内核启动时便将具有compatible属性的gled@0和gled@1节点都转换为平台设备platform_device，当平台驱动platform_driver伴随着设备驱动模块加载时与platform_device匹配。
  #define OFF 'C'
	#define ON  'O'
	#define LOW  0
	#define HIGH 1
	gled@0 {
		compatible = "glen,led_drv";
		led_pin = <
			OFF
			LOW
			26
			3
			0x020C406C 
			0x020E0068 
			0x020E02F4 
			0x0209C000 
			0x0209C004 
		>;
	};

	gled@1 {
		compatible = "glen,led_drv";
		led_pin = <
			ON
			LOW
			30
			1
			0x020C406C 
			0x0229000C 
			0x02290050 
			0x020AC000 
			0x020AC004 
		>;
	};
  1. 稍微修改imx6_gpio_drv.c文件
/**
 * @file imx6_gpio_drv.c
 * @author glen (glen_cao@126.com)
 * @brief 
 * @version 0.1
 * @date 2021-12-24
 * 
 * @copyright Copyright (c) 2021
 * 
 */

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/gpio.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <asm/mach/map.h>
#include <asm/uaccess.h>
#include <asm/io.h>

#include "led_dev.h"

static struct gled_device gled[16];

static void imx6_gled_ctrl(u8 idx, u8 status);
static int imx6_gled_init(u8 idx);
static int imx6_gled_exit(u8 idx);

static struct led_ops imx6_gpio_led_ops = {
    .num = 0,
    .led_init = imx6_gled_init,
    .led_exit = imx6_gled_exit, 
    .led_ctrl = imx6_gled_ctrl,
};

/**
 * @brief   : 打开/关闭LED 
 * @par     : status    LEDON('O') 打开LED, LEDOFF('C') 关闭LED
 * @retval  : 无
 */
static void imx6_gled_ctrl(u8 idx, u8 status)
{
    u32 val = 0;

    if (gled[idx].vir_io.ccgr == NULL) 
        return;

    if (status == ON) {
        val = readl(gled[idx].vir_io.dr);
        if (gled[idx].on_level == HIGH) {
            val |= (1 << (gled[idx].pin));
        } else if (gled[idx].on_level == LOW) {
            val &= ~(1 << gled[idx].pin);
        }
        writel(val, gled[idx].vir_io.dr);
        printk("The led%d is openned!\r\n", idx);
    } else if (status == OFF) {
        val = readl(gled[idx].vir_io.dr);
        if (gled[idx].on_level == HIGH) {
            val &= ~(1 << gled[idx].pin);
        } else if (gled[idx].on_level == LOW) {
            val |= (1 << (gled[idx].pin));
        }
        writel(val, gled[idx].vir_io.dr);
        printk("The led%d is closed!\r\n", idx);
    } else {
        printk("Recived parameter is error!\r\n");
    }
}

/**
 * @brief LED状态初始化
 * @param idx LED
 */
static int imx6_gled_init(u8 idx)
{
    u32 val;

    if (idx >= imx6_gpio_led_ops.num) {
        return -EIO;
    }

    /* 寄存器地址映射 */
    gled[idx].vir_io.ccgr    = ioremap(gled[idx].phy_io.ccgr  ,  4);
    gled[idx].vir_io.sw_mux  = ioremap(gled[idx].phy_io.sw_mux,  4);
    gled[idx].vir_io.sw_pad  = ioremap(gled[idx].phy_io.sw_pad,  4);
    gled[idx].vir_io.dr      = ioremap(gled[idx].phy_io.dr    ,  4);
    gled[idx].vir_io.dir     = ioremap(gled[idx].phy_io.dir   ,  4);

    /* 使能GPIO时钟 */
    val = readl(gled[idx].vir_io.ccgr);
    val |= (3 << gled[idx].clk_shft_bits);
    writel(val, gled[idx].vir_io.ccgr);

    /* 设置gpio1_io03的复用功能 */
    writel(5, gled[idx].vir_io.sw_mux);

    /* 寄存器sw_mux1_io03设置IO属性 */
    writel(0x10B0, gled[idx].vir_io.sw_pad);

    /* 设置gpio1_gdir为输出功能 */
    val = readl(gled[idx].vir_io.dir);
    val |= (1 << gled[idx].pin);
    writel(val, gled[idx].vir_io.dir);

    /* 设置led为默认状态 */
    val = readl(gled[idx].vir_io.dr);
    if (gled[idx].dft_status == ON) {
        if (gled[idx].on_level == HIGH) {
            val |= (1 << gled[idx].pin);
        } else if (gled[idx].on_level == LOW) {
            val &= ~(1 << gled[idx].pin);
        }
    } else if (gled[idx].dft_status == OFF) {
        if (gled[idx].on_level == HIGH) {
            val &= ~(1 << gled[idx].pin);
        } else if (gled[idx].on_level == LOW) {
            val |= (1 << gled[idx].pin);
        }
    }
    writel(val, gled[idx].vir_io.dr);

    return 0;
}

/**
 * @brief LED状态解初始化
 * @param idx LED
 */
static int imx6_gled_exit(u8 idx)
{
    if (idx >= imx6_gpio_led_ops.num) {
        return -EIO;
    }
    iounmap(gled[idx].vir_io.ccgr);
    iounmap(gled[idx].vir_io.sw_mux);
    iounmap(gled[idx].vir_io.sw_pad);
    iounmap(gled[idx].vir_io.dr);
    iounmap(gled[idx].vir_io.dir);

    return 0;
}

/**
 * @brief 
 */
static int imx6_gpio_probe(struct platform_device *pdev)
{
    u8 i = 0;
    int ret;

    struct device_node *nd = pdev->dev.of_node;

    if (!nd) 
        return -1;

    i = imx6_gpio_led_ops.num;

    ret = of_property_read_u32_array(nd, "led_pin", (u32 *)&gled[i], 9);
    if (ret < 0) 
        printk("Read property \"led_pin\" failed!\r\n");
    else {
        printk("led_pin data:");
        for (ret = 0; ret < 9; ret++) {
            printk("%#X\t", ((u32 *)&(gled[i]))[ret]);
        }
        printk("\r\n");
    }

    /* 创建设备节点 */
    led_device_create(i);
    imx6_gpio_led_ops.num++;
    
    return 0;
}

static int imx6_gpio_remove(struct platform_device *pdev)
{
    u8 i;

    /* 销毁设备节点 */
    for (i = 0; i < imx6_gpio_led_ops.num; i++) {
        led_device_destroy(i);
    }
    imx6_gpio_led_ops.num = 0;

    return 0;
}

static const struct of_device_id gled_devs[] = {
    {.compatible = "glen,led_drv"},
    { },
};

static struct platform_driver imx6_gpio_driver = {
    .driver = {
        .name = "gled",
        .of_match_table = gled_devs,
    },
    .probe = imx6_gpio_probe,
    .remove = imx6_gpio_remove,
};

static int __init imx6_gpio_drv_init(void)
{
    int ret;

    ret = platform_driver_register(&imx6_gpio_driver);
    if (ret)
        pr_err("Unable to initialize imx6 gpio driver\n");
    else
        pr_info("The imx6 gpio driver is registered.\n");
    
    led_ops_register(&imx6_gpio_led_ops);

    return ret;
}

static void __exit imx6_gpio_drv_exit(void)
{
    platform_driver_unregister(&imx6_gpio_driver);
}
module_init(imx6_gpio_drv_init);
module_exit(imx6_gpio_drv_exit);

/* insert license for module */
MODULE_LICENSE("GPL");

/* insert author information for module */
MODULE_AUTHOR("glen");
  1. led_drv.c文件不作修改
  2. Makefile文件删除atk_board_led.o文件
KERNELDIR	:= /home/glen/linux/imx6ull/linux/glen_linux
CURRENT_PATH	:= $(shell pwd)
#led_driver-y	:= led_drv.o led_dev.o
obj-m	+= led_drv.o imx6_gpio_drv.o
build:	kernel_modules

kernel_modules:
	$(MAKE) -C $(KERNELDIR) M=$(CURRENT_PATH) modules

clean:
	$(MAKE) -C $(KERNELDIR) M=$(CURRENT_PATH) clean
  1. 测试程序不做更改，验证参考Linux学习笔记（15）——LED设备驱动
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