内核&vermagic

  linux驱动学习正式开始，开发板：TQ210，在网上搜索资料点亮OLED，先贴出代码：
led_driver.c

/**********************************************************
 **CopyRight OuYanghan
 **filename            : led_driver.c
 **decription        : driver layer
 **author            : OuYanghan
 **date                : 2017.11.08
 **********************************************************/

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <asm/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <linux/device.h>//classcreate的定义
#include <linux/gpio.h>//gpio结构体的定义
//#include <mach/regs-gpio.h>

//#include <asm/arch/regs-gpio.h>
//linux 3.10内核的regs-gpio.h位置不再是<asm/arch/regs-gpio.h>
#include <mach/hardware.h>
#include <linux/platform_device.h>

volatile unsigned long *gpc0con = NULL;
volatile unsigned long *gpc0pud = NULL;
volatile unsigned long *gpc0dat = NULL;

static struct class *led_drv_class;
static struct device *led_drv_class_dev;

///static volatile unsigned long *gpio_con;
//static volatile unsigned long *gpio_dat;

static int led_open(struct inode *inode, struct file *file)
{
    printk("led_drv_open\n");

    *gpc0con &= ~(0xf<<3*4);
    *gpc0con |= (0x1<<3*4);//1为输出模式
    *gpc0dat &= ~(0x1<<3);//gpc0_3
    *gpc0dat |= (0x0<<3);//高电平亮

    return 0;
}

static ssize_t led_write(struct file *file, const char __user *buf, size_t count, loff_t * ppos)
{

    int val;
    int ret;
    printk("led_drv_write\n");

    ret = copy_from_user(&val, buf, count); // copy_to_user();
    if(ret)
    {
        printk("copy_from_user error\n");
        return -EFAULT;
    }
    if (val == 1)
    {
        *gpc0dat &= ~(0x1<<3);//高电平亮
        *gpc0dat |= (0x1<<3);
    }
    else
    {
        // gpc0dat = (*gpc0dat & ~(0x1<<3)) | (0x1<<3);
        *gpc0dat &= ~(0x1<<3);//
        *gpc0dat |= (0x0<<3);
    }

    return 0;
}

static struct file_operations led_fops = {
    .owner = THIS_MODULE,
    .open = led_open,
    .write = led_write,
};

int major;
static int led_probe(struct platform_device *pdev)
{
    struct resource *res;
    /* 根据platform_device的资源进行ioremap */
    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    if(!res){
        printk("get resource error\n");
        return -1;
    }
    gpc0con = ioremap(res->start, res->end - res->start + 1);
    gpc0dat = gpc0con + 1;

    major = register_chrdev(0, "led_cdev", &led_fops);
    led_drv_class = class_create(THIS_MODULE,"class_led_cdev");
    led_drv_class_dev = device_create(led_drv_class, NULL,MKDEV(major, 0), NULL, "led_rocky");
    //MKDEV将主设备号和次设备号转为dev_t类型
    //device_create创建设备信息，udev会自动根据设备信息创建设备节点/dev/led，应用程序根据设备节点(路径)访问设备
    //linux 3.10中，class_device_create替换为device_create
    printk("led_rocky initialize\n");
    return 0;
}

static int led_remove(struct platform_device *pdev)
{
    printk("led_drv_exit\n");
    unregister_chrdev(major, "led_cdev");
    device_unregister(led_drv_class_dev);//linux 3.10中，class_device_unregister替换为device_unregister
    class_destroy(led_drv_class);
    return 0;
}

struct platform_driver led_drv = {
    .probe = led_probe,
    .remove = led_remove,
    .driver = {
        .owner = THIS_MODULE, /* 一定要加上这句，否则运行测试程序会出现段错误 */
        .name = "s5pv210_led",
    }
};

static int __init led_drv_init(void)
{
    platform_driver_register(&led_drv);
    return 0;
}

static void __exit led_drv_exit(void)
{
    platform_driver_unregister(&led_drv);
}

module_init(led_drv_init);
module_exit(led_drv_exit);

MODULE_LICENSE("GPL");

led_test.c:

/**********************************************************
 **CopyRight OuYanghan
 **filename            : led_test.c
 **decription        : user test demo
 **author            : OuYanghan
 **date                : 2017.11.08
 **********************************************************/

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

/* ledtest on
 * ledtest off
 */
int main(int argc, char **argv)
{
    int fd;
    int val = 1;
    fd = open("/dev/led_rocky", O_RDWR);
    if (fd < 0)
    {
        printf("can't open!\n");
    }
    if (argc != 2)
    {
        printf("Usage :\n");
        printf("%s \n", argv[0]);
        return 0;
    }

    if (strcmp(argv[1], "on") == 0)
    {
        val = 1;
    }
    else
    {
        val = 0;
    }

    write(fd, &val, 4);
    return 0;
}

Makefile:

KERN_DIR = /home/rocky/practise/tq210learn/Kernel_3.0.8_TQ210_for_Linux_v2.1
obj-m += led_driver.o

target = main

.PHONY:all
all:
    make ARCH=arm -C $(KERN_DIR) M=`pwd` modules
    arm-linux-gcc -o $(target) led_test.c

.PHONY:clean
clean:
    rm -rf $(target) *.ko *.mod.c *.mod.o *.o *.order *.symvers *.cmd .*.o.* .*.ko.*

问题一. 写好这三个文件之后，能猜测到Makefile中的“KERN_DIR”是指内核的根目录路径，为什么要去执行该目录下的makefile？
    带着问题我去找了tq提供的linux3.0.8，尝试着执行make menuconfig配置下内核，于是出现了问题二。

问题二. p { margin-bottom: 0.25cm; line-height: 120% 解压天嵌提供的linux内核3.0.8版本，在根目录下执行make menuconfig，提示下面错误：

*** Unable to find the ncurses libraries or the

*** required header files.

*** 'make menuconfig' requires the ncurses libraries.

***

*** Install ncurses (ncurses-devel) and try again.

***

/home/rocky/practise/tq210learn/Kernel_3.0.8_TQ210_for_Linux_v2.1/scripts/kconfig/Makefile:215: recipe for target 'scripts/kconfig/dochecklxdialog' failed

make[1]: *** [scripts/kconfig/dochecklxdialog] Error 1

Makefile:492: recipe for target 'menuconfig' failed

make: *** [menuconfig] Error 2

解决方法：
    根据提示知：缺少终端图形库ncurses库，下载ncurse-devel，报错，正确打开方式：sudo apt-get install libncurses5-dev！！

然后尝试在led测试代码目录下执行make，得到文件如下：

led_driver.c  led_driver.ko  led_driver.mod.c  led_driver.mod.o  led_driver.o  led_test.c  main  Makefile  modules.order  Module.symvers

然后将led_driver.ko 和目标文件main拷贝到开发板上，运行insmod led_driver.ko，报错，问题三：
问题三：提示错误如下：

td p { margin-bottom: 0cm; }p { margin-bottom: 0.25cm; line-height: 120%; }

led_driver: version magic '3.0.8 mod_unload ARMv5 ' should be '3.0.8-EmbedSky preempt mod_unload ARMv7 '

insmod: can't insert 'led_driver.ko': invalid module format

解决方法：
     step1.其中搜索了很多资料，直接搜索问题，也知道是因为vermagic的问题，就是你拿在自己内核版本里编译的ko文件，在目标开发板上insmod的时候，目标开发板内核会检测这个vermagic的值，其实就是一串字符串。不过出发点不多，都是在搜出现的问题，弄了两天没找到解决方法，于是换了思路直接搜索vermagic的概念，才有了突破。以我使用的Linux3.0.8为例：
     step2.vermagic由include/generated/utsrelease.h文件定义VERMAGIC_STRING：

#include <generated/utsrelease.h>
#include <linux/module.h>

/* Simply sanity version stamp for modules. */
#ifdef CONFIG_SMP
#define MODULE_VERMAGIC_SMP "SMP "
#else
#define MODULE_VERMAGIC_SMP ""
#endif
#ifdef CONFIG_PREEMPT
#define MODULE_VERMAGIC_PREEMPT "preempt "
#else
#define MODULE_VERMAGIC_PREEMPT ""
#endif
#ifdef CONFIG_MODULE_UNLOAD
#define MODULE_VERMAGIC_MODULE_UNLOAD "mod_unload "
#else
#define MODULE_VERMAGIC_MODULE_UNLOAD ""
#endif
#ifdef CONFIG_MODVERSIONS
#define MODULE_VERMAGIC_MODVERSIONS "modversions "
#else
#define MODULE_VERMAGIC_MODVERSIONS ""
#endif
#ifndef MODULE_ARCH_VERMAGIC
#define MODULE_ARCH_VERMAGIC ""
#endif

#define VERMAGIC_STRING                         \
    UTS_RELEASE " "                            \
    MODULE_VERMAGIC_SMP MODULE_VERMAGIC_PREEMPT             \
    MODULE_VERMAGIC_MODULE_UNLOAD MODULE_VERMAGIC_MODVERSIONS    \
    MODULE_ARCH_VERMAGIC

    step3.然后UTS_RELEASE查找其位置，include/generated/utsrelease.h，如下图，将其改为3.0.8-EmbedSky，：

#define UTS_RELEASE "3.0.8"

重新make，insmod加载时未提示上述错误，运行测试文件，提示“can not open”，查看以下/dev下并没有出现我创建的文件节点！！
好吧这次就到这里，我要继续学习韦东山老师的视频，立帖为证，这个问题我还会回来的。