使用設備樹來編寫led驅動程序

在總線設備驅動模型中，平台設備是寫在c文件中。使用設備樹時，平台設備事先並不存在，在dts文件中構造節點，節點里面含有資源。dts文件被編譯成dtb文件，然后傳遞給內核。內核會解析dtb文件，得到一個個device_node，每個節點對應一個device_node結構體，每個device_node結構體變成一個platform_device結構體，該結構體中就含有資源，這些資源來源於dts文件。接下來的處理過程和總線設備驅動模型就一樣了，如果設備與驅動相匹配，就調用驅動中的probe函數。可以這么認為，設備樹是對總線設備驅動模型的一種改進，它仍然屬於總線設備驅動模型的一種。

看一下這個設備樹文件：

// SPDX-License-Identifier: GPL-2.0
/*
 * SAMSUNG SMDK2440 board device tree source  4  *  5  * Copyright (c) 2018 [e-mail]  6  * dtc -I dtb -O dts -o jz2440.dts jz2440.dtb  7  */
 //這里定義了一些宏，使用的是c語言的語法
#define S3C2410_GPA(_nr)    ((0<<16) + (_nr))
#define S3C2410_GPB(_nr)    ((1<<16) + (_nr))
#define S3C2410_GPC(_nr)    ((2<<16) + (_nr))
#define S3C2410_GPD(_nr)    ((3<<16) + (_nr))
#define S3C2410_GPE(_nr)    ((4<<16) + (_nr))
#define S3C2410_GPF(_nr)    ((5<<16) + (_nr))
#define S3C2410_GPG(_nr)    ((6<<16) + (_nr))
#define S3C2410_GPH(_nr)    ((7<<16) + (_nr))
#define S3C2410_GPJ(_nr)    ((8<<16) + (_nr))
#define S3C2410_GPK(_nr)    ((9<<16) + (_nr))
#define S3C2410_GPL(_nr)    ((10<<16) + (_nr))
#define S3C2410_GPM(_nr)    ((11<<16) + (_nr))

/dts-v1/; 23 
/ { 25     model = "SMDK24440"; 26     compatible = "samsung,smdk2440"; 27 
    #address-cells = <1>; 29     #size-cells = <1>; 30         
    memory@30000000 { 32         device_type = "memory"; 33         reg =  <0x30000000 0x4000000>; 34  }; 35 /*
 cpus { 37  cpu { 38  compatible = "arm,arm926ej-s"; 39  }; 40  }; 41 */    
 chosen { //設置了內核的命令行參數 43         bootargs = "noinitrd root=/dev/mtdblock4 rw init=/linuxrc console=ttySAC0,115200"; 44  }; 45 
    
 led { 48         compatible = "jz2440_led"; //以后就使用compatible在內核里面找到能夠支持這個節點的驅動程序，即找到能夠支持這個節點的平台drv. 49         reg = <S3C2410_GPF(5) 1>;//reg是register的縮寫。在arm系統里面，寄存器和內存是被同樣對待的，因為寄存器的訪問空間與內存的訪問空間沒什么差別。 50  }; 51 };

 單板啟動之后，

cd /sys/devices/platform/

ls 下會看到xxxxxxx，假設是50005.led。

cd 50005.led

ls會看到這樣的文件

driver_override    of_node       subsystem      modalias      power   uevent

cd of_node 

ls

compatible     name      reg

cat compatible     就會顯示  jz2440_led

cat  name             就會顯示led

hexdump -C reg

對應着8個字節，

00 05   00 05  00  00  00  01

對應着兩個數值，來源於    reg = <S3C2410_GPF(5) 1>

00 05   00 05    對應S3C2410_GPF(5)代表着寄存器的起始地址，對應着這個宏    #define S3C2410_GPF(_nr) ((5<<16) + (_nr))，表示高16位是5，低16位也是5.

00 00 00 01對應着是1，本意就是寄存器的大小。

在總線設備驅動模型中，是通過名字來進行設備與驅動的匹配。那么在利用設備樹時，是利用什么進行匹配的呢。

static int platform_match(struct device *dev, struct device_driver *drv)  2 {  3     struct platform_device *pdev = to_platform_device(dev);  4     struct platform_driver *pdrv = to_platform_driver(drv);  5 
    /* Attempt an OF style match first */
    if (of_driver_match_device(dev, drv))//用來判斷從設備樹中得到的platform_devcie與提供的platform_drv
　　　　　　　　　　　　　　　　　　　　　　　　　//是否匹配，  8         return 1;  9 
    /* Then try to match against the id table */
    if (pdrv->id_table) 12         return platform_match_id(pdrv->id_table, pdev) != NULL; 13 
    /* fall-back to driver name match */
    return (strcmp(pdev->name, drv->name) == 0); 16 }

static inline int of_driver_match_device(struct device *dev, 2                      const struct device_driver *drv) 3 {
　　/*從這里可以看出，平台drv中有個成員變量，of_match_table*/ 4     return of_match_device(drv->of_match_table, dev) != NULL; 5 }

struct device_driver {  2     const char        *name;  3     struct bus_type        *bus;  4 
    struct module        *owner;  6     const char        *mod_name;    /* used for built-in modules */

    bool suppress_bind_attrs;    /* disables bind/unbind via sysfs */

    const struct of_device_id    *of_match_table; //該指針指向一項或多項of_device_id

    int (*probe) (struct device *dev); 13     int (*remove) (struct device *dev); 14     void (*shutdown) (struct device *dev); 15     int (*suspend) (struct device *dev, pm_message_t state); 16     int (*resume) (struct device *dev); 17     const struct attribute_group **groups; 18 
    const struct dev_pm_ops *pm; 20 
    struct driver_private *p; 22 };

struct of_device_id  2 {  3     char    name[32];  4     char    type[32];  5     char    compatible[128];//從dts里得到的platform_device里有compatible屬性，兩者比較，如果一樣的話，就是匹配。  6 #ifdef __KERNEL__  7     void    *data;  8 #else
 kernel_ulong_t data; 10 #endif
};

struct platform_device {  2     const char    * name;  3     int id;  4     struct device dev;//對於dts生成的設備platform_device，這里含有Of_node,of_node中含有屬性，這含有哪些屬性呢，這取決於設備樹，比如：
 //compatible pin等。這個compatible屬性用來尋找支持它的platform_driver.這個compatible是最優先比較。  5  u32 num_resources;  6     struct resource    * resource;  7 
    const struct platform_device_id    *id_entry;  9 
    /* MFD cell pointer */
    struct mfd_cell *mfd_cell; 12 
    /* arch specific additions */
    struct pdev_archdata archdata; 15 };

 

 

利用設備樹編寫的led驅動程序如下：

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>

#define S3C2440_GPA(n)  (0<<16 | n)
#define S3C2440_GPB(n)  (1<<16 | n)
#define S3C2440_GPC(n)  (2<<16 | n)
#define S3C2440_GPD(n)  (3<<16 | n)
#define S3C2440_GPE(n)  (4<<16 | n)
#define S3C2440_GPF(n)  (5<<16 | n)
#define S3C2440_GPG(n)  (6<<16 | n)
#define S3C2440_GPH(n)  (7<<16 | n)
#define S3C2440_GPI(n)  (8<<16 | n)
#define S3C2440_GPJ(n)  (9<<16 | n)

static int led_pin;  26 static volatile unsigned int *gpio_con;  27 static volatile unsigned int *gpio_dat;  28 
/* 123. 分配/設置/注冊file_operations  30  * 4. 入口  31  * 5. 出口  32  */

static int major;  35 static struct class *led_class;  36 
static unsigned int gpio_base[] = {  38     0x56000000, /* GPACON */
    0x56000010, /* GPBCON */
    0x56000020, /* GPCCON */
    0x56000030, /* GPDCON */
    0x56000040, /* GPECON */
    0x56000050, /* GPFCON */
    0x56000060, /* GPGCON */
    0x56000070, /* GPHCON */
    0,          /* GPICON */
    0x560000D0, /* GPJCON */
};  49 
static int led_open (struct inode *node, struct file *filp)  51 {  52     /* 把LED引腳配置為輸出引腳 */
    /* GPF5 - 0x56000050 */
    int bank = led_pin >> 16;  55     int base = gpio_base[bank];  56 
    int pin = led_pin & 0xffff;  58     gpio_con = ioremap(base, 8);  59     if (gpio_con) {  60         printk("ioremap(0x%x) = 0x%x\n", base, gpio_con);  61  }  62     else {  63         return -EINVAL;  64  }  65     
    gpio_dat = gpio_con + 1;  67 
    *gpio_con &= ~(3<<(pin * 2));  69     *gpio_con |= (1<<(pin * 2));  70 
    return 0;  72 }  73 
static ssize_t led_write (struct file *filp, const char __user *buf, size_t size, loff_t *off)  75 {  76     /* 根據APP傳入的值來設置LED引腳 */
    unsigned char val;  78     int pin = led_pin & 0xffff;  79     
    copy_from_user(&val, buf, 1);  81 
    if (val)  83  {  84         /* 點燈 */
        *gpio_dat &= ~(1<<pin);  86  }  87     else
 {  89         /* 滅燈 */
        *gpio_dat |= (1<<pin);  91  }  92 
    return 1; /* 已寫入1個數據 */
}  95 
static int led_release (struct inode *node, struct file *filp)  97 {  98     printk("iounmap(0x%x)\n", gpio_con);  99  iounmap(gpio_con); 100     return 0; 101 } 102 

static struct file_operations myled_oprs = { 105     .owner = THIS_MODULE, 106     .open  = led_open, 107     .write = led_write, 108     .release = led_release, 109 }; 110 

static int led_probe(struct platform_device *pdev) 113 { 114     struct resource        *res; 115 
    /* 根據platform_device的資源進行ioremap */
    res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 118     led_pin = res->start; 119 
    major = register_chrdev(0, "myled", &myled_oprs); 121 
    led_class = class_create(THIS_MODULE, "myled"); 123     device_create(led_class, NULL, MKDEV(major, 0), NULL, "led"); /* /dev/led */
    
    return 0; 126 } 127 
static int led_remove(struct platform_device *pdev) 129 { 130     unregister_chrdev(major, "myled"); 131     device_destroy(led_class,  MKDEV(major, 0)); 132  class_destroy(led_class); 133     
    return 0; 135 } 136 

static const struct of_device_id of_match_leds[] = { 139     { .compatible = "jz2440_led", .data = NULL }, 140     { /* sentinel */ } 141 }; 142 

struct platform_driver led_drv = { 145     .probe        = led_probe, 146     .remove        = led_remove, 147     .driver        = { 148         .name    = "myled", 149         .of_match_table = of_match_leds, /* 能支持哪些來自於dts的platform_device */
 } 151 }; 152 

static int myled_init(void) 155 { 156     platform_driver_register(&led_drv); 157     return 0; 158 } 159 
static void myled_exit(void) 161 { 162     platform_driver_unregister(&led_drv); 163 } 164 


module_init(myled_init); 168 module_exit(myled_exit); 169 

MODULE_LICENSE("GPL");

 在設備樹中形如下面這樣的寫法太別扭了

reg = <S3C2410_GPF(5) 1>;  

S3C2410_GPF(5)這個地方本來定義了引腳，你非要把它當做register。看一下能否將register去掉，能不能使用另外一種方法指定引腳。

// SPDX-License-Identifier: GPL-2.0
/*
 * SAMSUNG SMDK2440 board device tree source  4  *  5  * Copyright (c) 2018 [e-mail]  6  * dtc -I dtb -O dts -o jz2440.dts jz2440.dtb  7  */
 
#define S3C2410_GPA(_nr)    ((0<<16) + (_nr))
#define S3C2410_GPB(_nr)    ((1<<16) + (_nr))
#define S3C2410_GPC(_nr)    ((2<<16) + (_nr))
#define S3C2410_GPD(_nr)    ((3<<16) + (_nr))
#define S3C2410_GPE(_nr)    ((4<<16) + (_nr))
#define S3C2410_GPF(_nr)    ((5<<16) + (_nr))
#define S3C2410_GPG(_nr)    ((6<<16) + (_nr))
#define S3C2410_GPH(_nr)    ((7<<16) + (_nr))
#define S3C2410_GPJ(_nr)    ((8<<16) + (_nr))
#define S3C2410_GPK(_nr)    ((9<<16) + (_nr))
#define S3C2410_GPL(_nr)    ((10<<16) + (_nr))
#define S3C2410_GPM(_nr)    ((11<<16) + (_nr))

/dts-v1/; 23 
/ { 25     model = "SMDK24440"; 26     compatible = "samsung,smdk2440"; 27 
    #address-cells = <1>; 29     #size-cells = <1>; 30         
    memory@30000000 { 32         device_type = "memory"; 33         reg =  <0x30000000 0x4000000>; 34  }; 35 /*
 cpus { 37  cpu { 38  compatible = "arm,arm926ej-s"; 39  }; 40  }; 41 */    
 chosen { 43         bootargs = "noinitrd root=/dev/mtdblock4 rw init=/linuxrc console=ttySAC0,115200"; 44  }; 45 
    
 led { 48         compatible = "jz2440_led"; 49         pin = <S3C2410_GPF(5)>; 50  }; 51 };

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/uaccess.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>

#define S3C2440_GPA(n)  (0<<16 | n)
#define S3C2440_GPB(n)  (1<<16 | n)
#define S3C2440_GPC(n)  (2<<16 | n)
#define S3C2440_GPD(n)  (3<<16 | n)
#define S3C2440_GPE(n)  (4<<16 | n)
#define S3C2440_GPF(n)  (5<<16 | n)
#define S3C2440_GPG(n)  (6<<16 | n)
#define S3C2440_GPH(n)  (7<<16 | n)
#define S3C2440_GPI(n)  (8<<16 | n)
#define S3C2440_GPJ(n)  (9<<16 | n)

static int led_pin;  26 static volatile unsigned int *gpio_con;  27 static volatile unsigned int *gpio_dat;  28 
/* 123. 分配/設置/注冊file_operations  30  * 4. 入口  31  * 5. 出口  32  */

static int major;  35 static struct class *led_class;  36 
static unsigned int gpio_base[] = {  38     0x56000000, /* GPACON */
    0x56000010, /* GPBCON */
    0x56000020, /* GPCCON */
    0x56000030, /* GPDCON */
    0x56000040, /* GPECON */
    0x56000050, /* GPFCON */
    0x56000060, /* GPGCON */
    0x56000070, /* GPHCON */
    0,          /* GPICON */
    0x560000D0, /* GPJCON */
};  49 
static int led_open (struct inode *node, struct file *filp)  51 {  52     /* 把LED引腳配置為輸出引腳 */
    /* GPF5 - 0x56000050 */
    int bank = led_pin >> 16;  55     int base = gpio_base[bank];  56 
    int pin = led_pin & 0xffff;  58     gpio_con = ioremap(base, 8);  59     if (gpio_con) {  60         printk("ioremap(0x%x) = 0x%x\n", base, gpio_con);  61  }  62     else {  63         return -EINVAL;  64  }  65     
    gpio_dat = gpio_con + 1;  67 
    *gpio_con &= ~(3<<(pin * 2));  69     *gpio_con |= (1<<(pin * 2));  70 
    return 0;  72 }  73 
static ssize_t led_write (struct file *filp, const char __user *buf, size_t size, loff_t *off)  75 {  76     /* 根據APP傳入的值來設置LED引腳 */
    unsigned char val;  78     int pin = led_pin & 0xffff;  79     
    copy_from_user(&val, buf, 1);  81 
    if (val)  83  {  84         /* 點燈 */
        *gpio_dat &= ~(1<<pin);  86  }  87     else
 {  89         /* 滅燈 */
        *gpio_dat |= (1<<pin);  91  }  92 
    return 1; /* 已寫入1個數據 */
}  95 
static int led_release (struct inode *node, struct file *filp)  97 {  98     printk("iounmap(0x%x)\n", gpio_con);  99  iounmap(gpio_con); 100     return 0; 101 } 102 

static struct file_operations myled_oprs = { 105     .owner = THIS_MODULE, 106     .open  = led_open, 107     .write = led_write, 108     .release = led_release, 109 }; 110 

static int led_probe(struct platform_device *pdev) 113 { 114     struct resource        *res; 115 
    /* 根據platform_device的資源進行ioremap */
    res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 118     if (res) { 119         led_pin = res->start; 120  } 121     else { 122         /* 獲得pin屬性 */
        of_property_read_s32(pdev->dev.of_node, "pin", &led_pin); 124  } 125 
    if (!led_pin) 127  { 128         printk("can not get pin for led\n"); 129         return -EINVAL; 130  } 131         

    major = register_chrdev(0, "myled", &myled_oprs); 134 
    led_class = class_create(THIS_MODULE, "myled"); 136     device_create(led_class, NULL, MKDEV(major, 0), NULL, "led"); /* /dev/led */
    
    return 0; 139 } 140 
static int led_remove(struct platform_device *pdev) 142 { 143     unregister_chrdev(major, "myled"); 144     device_destroy(led_class,  MKDEV(major, 0)); 145  class_destroy(led_class); 146     
    return 0; 148 } 149 

static const struct of_device_id of_match_leds[] = { 152     { .compatible = "jz2440_led", .data = NULL }, 153     { /* sentinel */ } 154 }; 155 

struct platform_driver led_drv = { 158     .probe        = led_probe, 159     .remove        = led_remove, 160     .driver        = { 161         .name    = "myled", 162         .of_match_table = of_match_leds, /* 能支持哪些來自於dts的platform_device */
 } 164 }; 165 

static int myled_init(void) 168 { 169     platform_driver_register(&led_drv); 170     return 0; 171 } 172 
static void myled_exit(void) 174 { 175     platform_driver_unregister(&led_drv); 176 } 177 


module_init(myled_init); 181 module_exit(myled_exit); 182 

MODULE_LICENSE("GPL");