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  • 【linux设备模型】之platform设备驱动

    一、platform总线、设备和驱动
        platform是一种虚拟总线,对应的设备称为platform_device,对应的驱动称为platform_driver。
    platform_device定义在<linux/platform_device.h>中:
     1 struct platform_device {
     2     const char    * name;
     3     int        id;
     4     struct device    dev;
     5     u32        num_resources;
     6     struct resource    * resource;
     7 
     8     const struct platform_device_id    *id_entry;
     9 
    10     /* arch specific additions */
    11     struct pdev_archdata    archdata;
    12 };
    当中的resource是platform驱动用到的资源,它是定义在<include/linux/ioport.h>中:
    1 struct resource {
    2     resource_size_t start;
    3     resource_size_t end;
    4     const char *name;
    5     unsigned long flags;
    6     struct resource *parent, *sibling, *child;
    7 };
    platform_driver定义在<linux/platform_device.h>中:
    1 struct platform_driver {
    2     int (*probe)(struct platform_device *);
    3     int (*remove)(struct platform_device *);
    4     void (*shutdown)(struct platform_device *);
    5     int (*suspend)(struct platform_device *, pm_message_t state);
    6     int (*resume)(struct platform_device *);
    7     struct device_driver driver;
    8     const struct platform_device_id *id_table;
    9 };
    系统中为platform总线定义了一个实例platform_bus_type,在<linux/platform_device.h>进行了声明:
    extern struct bus_type platform_bus_type;
    
    定义在drivers/base/platform.c中:
    1 struct bus_type platform_bus_type = {
    2     .name        = "platform",
    3     .dev_attrs    = platform_dev_attrs,
    4     .match        = platform_match,
    5     .uevent        = platform_uevent,
    6     .pm        = &platform_dev_pm_ops,
    7 };
    8 EXPORT_SYMBOL_GPL(platform_bus_type);
    二、详细实现
    1、platform_match函数的实现(定义在drivers/base/platform.c中)
     1 static const struct platform_device_id *platform_match_id(
     2             const struct platform_device_id *id,
     3             struct platform_device *pdev)
     4 {
     5     while (id->name[0]) {
     6         if (strcmp(pdev->name, id->name) == 0) {
     7             pdev->id_entry = id;
     8             return id;
     9         }
    10         id++;
    11     }
    12     return NULL;
    13 }
    14 
    15 /**
    16  * platform_match - bind platform device to platform driver.
    17  * @dev: device.
    18  * @drv: driver.
    19  *
    20  * Platform device IDs are assumed to be encoded like this:
    21  * "<name><instance>", where <name> is a short description of the type of
    22  * device, like "pci" or "floppy", and <instance> is the enumerated
    23  * instance of the device, like '0' or '42'.  Driver IDs are simply
    24  * "<name>".  So, extract the <name> from the platform_device structure,
    25  * and compare it against the name of the driver. Return whether they match
    26  * or not.
    27  */
    28 static int platform_match(struct device *dev, struct device_driver *drv)
    29 {
    30     struct platform_device *pdev = to_platform_device(dev);
    31     struct platform_driver *pdrv = to_platform_driver(drv);
    32 
    33     /* Attempt an OF style match first */
    34     if (of_driver_match_device(dev, drv))
    35         return 1;
    36 
    37     /* Then try to match against the id table */
    38     if (pdrv->id_table)
    39         return platform_match_id(pdrv->id_table, pdev) != NULL;
    40 
    41     /* fall-back to driver name match */
    42     return (strcmp(pdev->name, drv->name) == 0);
    43 }
    是通过device的name和driver的name进行匹配的。
    2、platform_device的定义和注冊
    
    
    platform_add_devices定义在drivers/base/platform.c中) 
    1 /**
     2  * platform_add_devices - add a numbers of platform devices
     3  * @devs: array of platform devices to add
     4  * @num: number of platform devices in array
     5  */
     6 int platform_add_devices(struct platform_device **devs, int num)
     7 {
     8     int i, ret = 0;
     9 
    10     for (i = 0; i < num; i++) {
    11         ret = platform_device_register(devs[i]);
    12         if (ret) {
    13             while (--i >= 0)
    14                 platform_device_unregister(devs[i]);
    15             break;
    16         }
    17     }
    18 
    19     return ret;
    20 }
    21 EXPORT_SYMBOL_GPL(platform_add_devices);
    对于一个指定的板子来说,比方对于ldd6410的globalfifo驱动来说,要在mach-ldd6410.c中定义platform_device globalfifo_device,并将globalfifo_device放入ldd6410_devices数组中,代码例如以下所看到的。
    
    
    3、platform_driver的操作
        platform_driver的定义和注冊在对应驱动文件里实现,以下是《linux驱动开发具体解释》一书中globalfifo的样例的部分代码:
    
    
    
    
    4、platform设备资源和数据
    (1)、resource的定义(<linux/ioport.h>)
    1 struct resource {
    2     resource_size_t start;
    3     resource_size_t end;
    4     const char *name;
    5     unsigned long flags;
    6     struct resource *parent, *sibling, *child;
    7 };
    当flags是IORESOURCE_MEM时,start和end各自是资源的起始地址和结束地址;
    当flags是IORESOURCE_IRQ时,start和end各自是资源的起始中断号和结束中断号;
    #define IORESOURCE_TYPE_BITS    0x00001f00    /* Resource type */
    #define IORESOURCE_IO         0x00000100
    #define IORESOURCE_MEM        0x00000200
    #define IORESOURCE_IRQ        0x00000400
    #define IORESOURCE_DMA        0x00000800
    #define IORESOURCE_BUS        0x00001000
    对于同种类型的资源能够有两份或多份。
    (2)、获得资源
    对resource的定义通常在板文件里,而驱动通过platform_get_resource获得资源(driver/base/platform.c):
     1 /**
     2  * platform_get_resource - get a resource for a device
     3  * @dev: platform device
     4  * @type: resource type
     5  * @num: resource index
     6  */
     7 struct resource *platform_get_resource(struct platform_device *dev,
     8                        unsigned int type, unsigned int num)
     9 {
    10     int i;
    11 
    12     for (i = 0; i < dev->num_resources; i++) {
    13         struct resource *r = &dev->resource[i];
    14 
    15         if (type == resource_type(r) && num-- == 0)
    16             return r;
    17     }
    18     return NULL;
    19 }
    20 EXPORT_SYMBOL_GPL(platform_get_resource);

    三、platform驱动的一个样例
    以linux-2.6.38内核的dm9000驱动为例说明平台驱动的定义和资源获取。
    1、platform_device和resource的定义(mach-mini6410.c)
     1 /* DM9000AEP 10/100 ethernet controller */
     2 /*dm9000的资源*/
     3 static struct resource mini6410_dm9k_resource[] = {
     4     [0] = {
     5         .start    = S3C64XX_PA_XM0CSN1,
     6         .end    = S3C64XX_PA_XM0CSN1 + 1,
     7         .flags    = IORESOURCE_MEM
     8     },
     9     [1] = {
    10         .start    = S3C64XX_PA_XM0CSN1 + 4,
    11         .end    = S3C64XX_PA_XM0CSN1 + 5,
    12         .flags    = IORESOURCE_MEM
    13     },
    14     [2] = {
    15         .start    = S3C_EINT(7),
    16         .end    = S3C_EINT(7),
    17         .flags    = IORESOURCE_IRQ | IORESOURCE_IRQ_HIGHLEVEL
    18     }
    19 };
    20 /*dm9000_plat_data定义在<linux/dm9000.h>*/
    21 static struct dm9000_plat_data mini6410_dm9k_pdata = {
    22     .flags        = (DM9000_PLATF_16BITONLY | DM9000_PLATF_NO_EEPROM),
    23 };
    24 
    25 static struct platform_device mini6410_device_eth = {
    26     .name        = "dm9000",
    27     .id        = -1,
    28     .num_resources    = ARRAY_SIZE(mini6410_dm9k_resource),
    29     .resource    = mini6410_dm9k_resource,
    30     .dev        = {
    31         .platform_data    = &mini6410_dm9k_pdata,
    32     },
    33 };
    34 
    35 /*全部的设备存放在这个数组里,最后通过platform_add_devices进行注冊*/
    36 static struct platform_device *mini6410_devices[] __initdata = {
    37     &mini6410_device_eth,
    38     &s3c_device_hsmmc0,
    39     &s3c_device_hsmmc1,
    40     &s3c_device_ohci,
    41     &s3c_device_nand,
    42     &s3c_device_fb,
    43     &mini6410_lcd_powerdev,
    44     &s3c_device_adc,
    45     &s3c_device_ts,
    46 };
    2、platform_driver的定义和注冊(dm9000.c)
     1 static struct platform_driver dm9000_driver = {
     2     .driver    = {
     3         .name    = "dm9000",
     4         .owner     = THIS_MODULE,
     5         .pm     = &dm9000_drv_pm_ops,
     6     },
     7     .probe   = dm9000_probe,
     8     .remove  = __devexit_p(dm9000_drv_remove),
     9 };
    10 
    11 static int __init
    12 dm9000_init(void)
    13 {
    14     printk(KERN_INFO "%s Ethernet Driver, V%s
    ", CARDNAME, DRV_VERSION);
    15 
    16     return platform_driver_register(&dm9000_driver);
    17 }
    18 
    19 static void __exit
    20 dm9000_cleanup(void)
    21 {
    22     platform_driver_unregister(&dm9000_driver);
    23 }
    dm9000驱动获得定义在板文件里的platform_data的方法:
    struct platform_device *pdev
    struct  dm9000_plat_data *pdata = pdev->dev.platform_data;
    db->addr_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    db->data_res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
    db->irq_res  = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
    platform_get_resource函数定义在drivers/base/platform.c中:
     1 /**
     2  * platform_get_resource - get a resource for a device
     3  * @dev: platform device
     4  * @type: resource type
     5  * @num: resource index
     6  */
     7 struct resource *platform_get_resource(struct platform_device *dev,
     8                        unsigned int type, unsigned int num)
     9 {
    10     int i;
    11 
    12     for (i = 0; i < dev->num_resources; i++) {
    13         struct resource *r = &dev->resource[i];
    14 
    15         if (type == resource_type(r) && num-- == 0)
    16             return r;
    17     }
    18     return NULL;
    19 }
    20 EXPORT_SYMBOL_GPL(platform_get_resource);

    參考:《linux驱动开发具体解释》
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  • 原文地址:https://www.cnblogs.com/blfshiye/p/3799943.html
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