Linux设备模型（下）之Platform

从Linux2.6内核起，引入一套新的驱动管理和注册机制：platform_device和 platform_driver 。Linux 中大部分的设备驱动，都可以使用这套机制，设备用 platform_device 表示；驱动用platform_driver 进行注册。 platform是一个虚拟的地址总线，相比pci，usb，它主要用于描述SOC上的片上资源，比如s3c2440上集成的控制器（lcd，watchdog，rtc等）， platform所描述的资源有一个共同点，就是在cpu的总线上直接取址。平台设备会分到一个名称(用在驱动绑定中)以及一系列诸如地址和中断请求号(IRQ)之类的资源.

struct platform_device {    const char * name;    intid;    struct device dev;    u32num_resources;    struct resource * resource; };

平台驱动遵循标准驱动模型的规范, 平台驱动按标准规范对电源管理和关机通告提供支 持

struct platform_driver {   int (*probe)(struct platform_device *);   int (*remove)(struct platform_device *);   void (*shutdown)(struct platform_device *);   int (*suspend)(struct platform_device *, pm_message_t state);   int (*suspend_late)(struct platform_device *, pm_message_t state);   int (*resume_early)(struct platform_device *);   int (*resume)(struct platform_device *);   struct device_driver driver;};

probe()总应该核实指定的设备硬件确实存在;平台设置代码有时不能确定这一点

 

系统为platform总线定义一个bus_type的实例platform_bus_type，通过其成员函数match()，确定device和driver如何匹配。

匹配platform_device和platform_driver主要看二者的name字段是否相同。（name必须要相同才能匹配）

 用platform_device_register(platform_device*)函数注册单个的平台设备。

一般是在平台的BSP文件中定义platform_device，通过platform_add_devices(platform_device*)函数将平台设备注册到系统中platform_driver 的注册与注销：

platform_driver_register(platform_driver*)

platform_driver_unregister(platform_driver*)

 

设备资源（struct resource)

关于资源的操作（平台设备会分到一系列诸如地址和中断请求号(IRQ)之类的资源)

struct resource {

   resource_size_t start;

   resource_size_t end;

   const char *name;

   unsigned long flags;

 // IORESOURCE_IO

 //IORESOURCE_MEM

 //IORESOURCE_IRQ

 //IORESOURCE_DMA

   struct resource *parent, *sibling, *child;

};

基于资源的分类（flags）有I/O端口、IRQ、DMA等等，而I/O端口又分为2种类型，IORESOURCE_IO（I/O映射） IORESOURCE_MEM（内存映射）CPU对外设IO端口物理地址的编址方式有2种：一种是IO映射方式（IO-mapped）， 另一种是内存映射方式（Memory-mapped）。具体采用哪一种方式则取决于CPU的体系结构。 像X86体系对外设就专门实现了一个单独地址空间，并且有专门的I/O指令来访问I/O端口，像ARM体系结构通常只是实现一个物理地址空间，I/O端口就被映射到CPU的单一物理地址空间中，而成为内存的一部分，所以一般资源都采用（IORESOURCE_MEM）。linux中对设备的资源按照资源树的结构来组织(其实就是一个链表结构的插入、删除、查找等操作），上面再添加设备（platform_device_add）的同时对相应的资源在资源树上进行插入操作

int insert_resource(struct resource *parent, struct resource *new)

 

关于platform resource有相关的函数进行对资源的操作。

struct resource *platform_get_resource(struct platform_device *, unsigned int, unsigned int);

int platform_get_irq(struct platform_device *, unsigned int);

struct resource *platform_get_resource_byname(struct platform_device *, unsigned int, char *);

int platform_get_irq_byname(struct platform_device *, char *);

例如s3c2440的watchdog资源分配实例：

watchdog寄存器的基地址为0x5300000

#define S3C2410_PA_WATCHDOG (0x53000000)

#define S3C24XX_SZ_WATCHDOG SZ_1M

static struct resource s3c_wdt_resource[] = {

   [0] = {

      .start = S3C24XX_PA_WATCHDOG,

      .end = S3C24XX_PA_WATCHDOG + S3C24XX_SZ_WATCHDOG - 1,

      .flags = IORESOURCE_MEM, //内存映射

   },

   [1] = {

      .start = IRQ_WDT,

      .end = IRQ_WDT,

      .flags = IORESOURCE_IRQ, //IRQ

   }

};

plat_button_device.c：

#include <linux/module.h>#include <linux/types.h>#include <linux/fs.h>#include <linux/init.h>#include <linux/platform_device.h>#include <mach/regs-gpio.h>#include <linux/interrupt.h>#include <linux/device.h>#include <linux/io.h>/*平台资源的定义*/static struct resource s3c_buttons_resource[] = {[0]={.start = S3C24XX_PA_GPIO,//                       (0x56000000).end   = S3C24XX_PA_GPIO + S3C24XX_SZ_GPIO - 1,//(0x56000000) + 0x00100000 -1 .flags = IORESOURCE_MEM,},[1]={.start = IRQ_EINT7,.end   = IRQ_EINT7,.flags = IORESOURCE_IRQ,},[2]={.start = IRQ_EINT1,.end   = IRQ_EINT1,.flags = IORESOURCE_IRQ,},[3]={.start = IRQ_EINT2,.end   = IRQ_EINT2,.flags = IORESOURCE_IRQ,},[4]={.start = IRQ_EINT3,.end   = IRQ_EINT3,.flags = IORESOURCE_IRQ,},[5]={.start = IRQ_EINT4,.end   = IRQ_EINT4,.flags = IORESOURCE_IRQ,},[6]={.start = IRQ_EINT5,.end   = IRQ_EINT5,.flags = IORESOURCE_IRQ,}};static struct platform_device *s3c_buttons;static int __init platform_init(void){    s3c_buttons = platform_device_alloc("gec2440-buttons",-1);    platform_device_add_resources(s3c_buttons,&s3c_buttons_resource,7);    /*平台设备的注册*/    platform_device_add(s3c_buttons);}static void __exit platform_exit(void){    platform_device_unregister(s3c_buttons);}module_init(platform_init);module_exit(platform_exit);MODULE_AUTHOR("Steven Bai");MODULE_LICENSE("GPL");MODULE_ALIAS("platform:gec2440buttons");

plat_button_driver.c：

#include <linux/module.h>#include <linux/types.h>#include <linux/miscdevice.h>#include <linux/fs.h>#include <linux/init.h>#include <linux/platform_device.h>#include <linux/interrupt.h>#include <linux/clk.h>#include <linux/uaccess.h>#include <linux/io.h>#include <mach/map.h>#include <mach/regs-gpio.h>#include <linux/poll.h>#include <linux/irq.h>#include <asm/unistd.h>#include <linux/device.h>#define DEVICE_NAME "buttons"static DECLARE_WAIT_QUEUE_HEAD(button_waitq);static volatile int ev_press = 0;static int key_value;static struct device     *buttons_dev;/* platform device attached to */static struct resource*buttons_mem;static struct resource   *buttons_irq;static void __iomem    *buttons_base;static int button_irqs[6];static irqreturn_t buttons_interrupt(int irq, void *dev_id){int i;for(i=0; i<6; i++){if(irq == button_irqs[i]){printk("==>interrput number:%d\n",irq);  key_value = i;ev_press =1;wake_up_interruptible(&button_waitq);}}    return IRQ_RETVAL(IRQ_HANDLED);}static int s3c24xx_buttons_open(struct inode *inode, struct file *file){int i;int err = 0;/*注册中断*/for(i=0; i<6; i++){if (button_irqs[i] < 0) continue;    /*中断触发方式：上升沿触发*/        err = request_irq(button_irqs[i],buttons_interrupt,IRQ_TYPE_EDGE_RISING,NULL,NULL);if(err)  break;}if (err) {i--;for (; i >= 0; i--) {if (button_irqs[i] < 0) {continue;}disable_irq(button_irqs[i]);free_irq(button_irqs[i], NULL);}return -EBUSY;}    ev_press = 0;       return 0;}static int s3c24xx_buttons_close(struct inode *inode, struct file *file){    int i;        for (i=0; i<6; i++) {if (button_irqs[i] < 0) {continue;}free_irq(button_irqs[i],NULL);    }    return 0;}static int s3c24xx_buttons_read(struct file *filp, char __user *buff, size_t count, loff_t *offp){    unsigned long err;    if (!ev_press) {if (filp->f_flags & O_NONBLOCK)return -EAGAIN;elsewait_event_interruptible(button_waitq, ev_press);    }        ev_press = 0;    err = copy_to_user(buff, &key_value, sizeof(key_value));    return sizeof(key_value);}static unsigned int s3c24xx_buttons_poll( struct file *file, struct poll_table_struct *wait){    unsigned int mask = 0;    poll_wait(file, &button_waitq, wait);    if (ev_press){        mask |= POLLIN | POLLRDNORM;}    return mask;}static struct file_operations gec2440buttons_fops = {    .owner   =   THIS_MODULE,    .open    =   s3c24xx_buttons_open,.release =   s3c24xx_buttons_close,    .read    =   s3c24xx_buttons_read,.poll    =   s3c24xx_buttons_poll,};static struct miscdevice gec2440_miscdev = {    .minor = MISC_DYNAMIC_MINOR,    .name = DEVICE_NAME,    .fops = &gec2440buttons_fops,};/* device interface */static int gec2440_buttons_probe(struct platform_device *pdev){struct resource *res;struct device *dev;int ret;int size;int i;printk("probe:%s\n", __func__);dev = &pdev->dev;buttons_dev = &pdev->dev;/*平台资源获取*/res = platform_get_resource(pdev, IORESOURCE_MEM, 0);if (res == NULL) {dev_err(dev, "no memory resource specified\n");return -ENOENT;}size = (res->end - res->start) + 1;buttons_mem = request_mem_region(res->start, size, pdev->name);if (buttons_mem == NULL) {dev_err(dev, "failed to get memory region\n");ret = -ENOENT;goto err_req;}buttons_base = ioremap(res->start, size);if (buttons_base == NULL) {dev_err(dev, "failed to ioremap() region\n");ret = -EINVAL;goto err_req;}printk(KERN_DEBUG"probe: mapped buttons_base=%p\n", buttons_base); /*get irq number*/for(i=0; i<6; i++){ buttons_irq = platform_get_resource(pdev,IORESOURCE_IRQ,i); if(buttons_irq == NULL) {dev_err(dev,"no irq resource specified\n");  ret = -ENOENT;  goto err_map;  }button_irqs[i] = buttons_irq->start;printk("button_irqs[%d]=%d\n",i,button_irqs[i]);  }ret = misc_register(&gec2440_miscdev);return 0; err_map:iounmap(buttons_base); err_req:release_resource(buttons_mem);kfree(buttons_mem);return ret;}static int gec2440_buttons_remove(struct platform_device *dev){release_resource(buttons_mem);kfree(buttons_mem);buttons_mem = NULL;iounmap(buttons_base);misc_deregister(&gec2440_miscdev);return 0;}/*平台驱动定义*/static struct platform_driver gec2440buttons_driver = {.probe= gec2440_buttons_probe,.remove= gec2440_buttons_remove,.driver= {.owner= THIS_MODULE,.name= "gec2440-buttons",},};static char banner[] __initdata = "gec2440 Buttons Driver\n";static int __init buttons_init(void){printk(banner);/*平台驱动注册*/platform_driver_register(&gec2440buttons_driver);return 0;}static void __exit buttons_exit(void){platform_driver_unregister(&gec2440buttons_driver);}module_init(buttons_init);module_exit(buttons_exit);MODULE_AUTHOR("Steven Bai");MODULE_DESCRIPTION("gec2440 Buttons Driver");MODULE_LICENSE("GPL");

 

开发板一上电后，可以/sys/bus/platform/下会挂上这个设备和对应的驱动