<平台设备设备驱动>
a:背景：
平台总线是Linux2.6的设备驱动模型中，关心总线，设备和驱动这3个实体。一个现实的Linux设备和驱动通常需要挂接在一种总线上(比如本身依附于PCI,USB,IIC,SPI等设备而言)。但是在嵌入式系统里面，SoC系统即集成的独立外设控制器，挂接在SoC内存空间的外设却没有这样的总线依附，为了和Linux设备驱动模型理论相互统一，Linux系统开发了Platform_bus这种虚拟总线，相应的设备叫做platform_device ,相应的驱动叫platform_driver。引入的一种虚拟总线，其优势是采用了总总线的模型对设备和驱动进行管理，同时提高程序的可移植性。
b:优势：
Linux platform_driver机制和传统的device_driver 机制(通过driver_register函数进行注册)相比，一个十分明显的优势在于platform机制将设备本身的资源注册进内核，由内核统一管理，在驱动程序中使用这些资源时通过platform device提供的标准接口进行申请并使用。这样提高了驱动和资源管理的独立性，并且拥有较好的可移植性和安全性(这些标准接口是安全的)
<平台设备驱动开发流程>
定义好了platform_device结构体后就可以调用函数platform_add_devices向系统中添加该设备了，之后可以调用platform_device_register()进行设备注册。要注意的是，这里的platform_device设备的注册过程必须在相应设备驱动加载之前被调用，即执行platform_driver_register之前,原因是因为驱动注册时需要匹配内核中所以已注册的设备名。
<平台总线>
a:内核数据结构
struct bus_type platform_bus_type = {
.name = "platform",
.dev_attrs = platform_dev_attrs,
.match = platform_match, //设备和驱动使用match函数来判断是否匹配
.uevent = platform_uevent,
.pm = PLATFORM_PM_OPS_PTR,
};
a-1:函数platform_match()
/* platform_match函数用于匹配总线中的驱动和设备 */
static int platform_match(struct device *dev, struct device_driver *drv)
{
struct platform_device *pdev = to_platform_device(dev);
struct platform_driver *pdrv = to_platform_driver(drv);
/* match against the id table first */
if (pdrv->id_table)
return platform_match_id(pdrv->id_table, pdev) != NULL;
/* fall-back to driver name match */
return (strcmp(pdev->name, drv->name) == 0);
}
platform_match函数首先判断是否由id_table，如果有则使用id_table来进行匹配，否则，判断platform_device和platform_driver成员里的name，如果二者的name字段相同则匹配，如果匹配则调用platform_driver的probe函数。
<平台设备>
a:内核数据结构
struct platform_device{
const char *name ;//设备名
int id;//设备编号，配合设备使用
struct device dev;
u32 num_resources;
struct resource *resource; //设备资源
}
a-1:设备资源
定义硬件资源，比如设备内存，中断号，DMA通道
struct resource{
resource_size_t char;
resource_size_t end;
const char *name;
unsigned long flags; //用于表明多个资源中的某一种资源，比如中断号，内存。
struct resource *parent,*siling ,*child;
};
a-1-1:"unsigned long flags",这里的flags可以取以下值，表示不同的设备资源
IORESOURCE_IO//IO资源
IORESOURCE_MEN//设备内存资源
IORESOURCE_IRQ//设备中断资源
IORESOURCE_DMA//设备DMA资源
a-1-2:一般驱动中调用该函数获得这些资源
int platform_get_irq(struct platform_device *dev, unsigned int num);
b:注册平台设备
int platform _device _register (struct platform_device *pdev )
<平台驱动>
a:内核数据结构
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 pm_ext_ops *pm;
struct device_driver driver;
};
a-1：函数int (*probe)(struct platform_device *);
static int s3c24xx_i2c_probe(struct platform_device *pdev)
{
struct s3c24xx_i2c *i2c = &s3c24xx_i2c;
struct resource *res;
int ret;
/* find the clock and enable it */
i2c->dev = &pdev->dev;
i2c->clk = clk_get(&pdev->dev, "i2c");
if (IS_ERR(i2c->clk)) {
dev_err(&pdev->dev, "cannot get clock\n");
ret = -ENOENT;
goto out;
}
dev_dbg(&pdev->dev, "clock source %p\n", i2c->clk);
clk_enable(i2c->clk);
/* map the registers */
res = platform_get_resource(pdev, IORESOURCE_MEM, 0); /* 获取设备的IO资源地址 */
if (res == NULL) {
dev_err(&pdev->dev, "cannot find IO resource\n");
ret = -ENOENT;
goto out;
}
i2c->ioarea = request_mem_region(res->start, (res->end-res->start)+1, pdev->name); /* 申请这块IO Region */
if (i2c->ioarea == NULL) {
dev_err(&pdev->dev, "cannot request IO\n");
ret = -ENXIO;
goto out;
}
i2c->regs = ioremap(res->start, (res->end-res->start)+1); /* 映射至内核虚拟空间 */
if (i2c->regs == NULL) {
dev_err(&pdev->dev, "cannot map IO\n");
ret = -ENXIO;
goto out;
}
dev_dbg(&pdev->dev, "registers %p (%p, %p)\n", i2c->regs, i2c->ioarea, res);
/* setup info block for the i2c core */
i2c->adap.algo_data = i2c;
i2c->adap.dev.parent = &pdev->dev;
/* initialise the i2c controller */
ret = s3c24xx_i2c_init(i2c);
if (ret != 0)
goto out;
/* find the IRQ for this unit (note, this relies on the init call to ensure no current IRQs pending */
res = platform_get_resource(pdev, IORESOURCE_IRQ, 0); /* 获取设备IRQ中断号 */
if (res == NULL) {
dev_err(&pdev->dev, "cannot find IRQ\n");
ret = -ENOENT;
goto out;
}
ret = request_irq(res->start, s3c24xx_i2c_irq, IRQF_DISABLED, pdev->name, i2c);申请IRQ
……
return ret;
}
b:注册总线驱动
int platform_driver_register(struct platform_driver*)
<平台私有数据>
a：struct platform_data{ }
设备除了可以再bsp中定义资源以外，还可以附加一些数据信息，因为对设备的硬件描述除了中断，内存，DMA通道以外，可能还会有一些配置信息，而这些配置信息也依赖于板，不宜直接放置在设备驱动本身，因此platform也提供了platform_data的支持，platform_data的形式是自定义的，比如对于dm9000网卡来说，platform_data中可以存放mac地址，总线宽度，板上有误eeprom等信息。
a-1:如对于 DM9000 网卡而言， platform_data 为一个 dm9000_plat_data 结构体，我们就可以将 MAC 地址、总线宽度、板上有无 EEPROM 信息等放入 platform_data：
static struct dm9000_plat_data ldd6410_dm9000_platdata = {
.flags = DM9000_PLATF_16BITONLY | DM9000_PLATF_NO_EEPROM,
.dev_addr = { 0x0, 0x16, 0xd4, 0x9f, 0xed, 0xa4 },
};
static struct platform_device ldd6410_dm9000 = {
.name= "dm9000",
.id= 0,
.num_resources= ARRAY_SIZE(ldd6410_dm9000_resource),
.resource =ldd6410_dm9000_resource,
.dev = {
.platform_data = &ldd6410_dm9000_platdata, //定义和初始化来自上面
}
};
<凭他设备驱动实例>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/ioport.h>
static struct resource beep_resource[] =
{
[0] ={
.start = 0x114000a0,
.end = 0x114000a0 + 0x4,
.flags = IORESOURCE_MEM,
},
[1] ={
.start = 0x139D0000,
.end = 0x139D0000 + 0x14,
.flags = IORESOURCE_MEM,
}
};
static void hello_release(struct device *dev)
{
printk("hello_release\n");
return ;
}
static struct platform_device hello_device=
{
.name = "bigbang",
.id = -1,
.dev.release = hello_release,
.num_resources = ARRAY_SIZE(beep_resource),
.resource = beep_resource,
};
static int hello_init(void)
{
printk("hello_init");
return platform_device_register(&hello_device);
}
static void hello_exit(void)
{
printk("hello_exit");
platform_device_unregister(&hello_device);
return;
}
MODULE_LICENSE("GPL");
module_init(hello_init);
module_exit(hello_exit);
2、driver.c
[cpp] view plain copy
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <asm/io.h>
static int major = 250;
static int minor=0;
static dev_t devno;
static struct class *cls;
static struct device *test_device;
#define TCFG0 0x0000
#define TCFG1 0x0004
#define TCON 0x0008
#define TCNTB0 0x000C
#define TCMPB0 0x0010
static unsigned int *gpd0con;
static void *timer_base;
#define MAGIC_NUMBER ‘k‘
#define BEEP_ON _IO(MAGIC_NUMBER ,0)
#define BEEP_OFF _IO(MAGIC_NUMBER ,1)
#define BEEP_FREQ _IO(MAGIC_NUMBER ,2)
static void fs4412_beep_init(void)
{
writel ((readl(gpd0con)&~(0xf<<0)) | (0x2<<0),gpd0con);
writel ((readl(timer_base +TCFG0 )&~(0xff<<0)) | (0xff <<0),timer_base +TCFG0);
writel ((readl(timer_base +TCFG1 )&~(0xf<<0)) | (0x2 <<0),timer_base +TCFG1 );
writel (500, timer_base +TCNTB0 );
writel (250, timer_base +TCMPB0 );
writel ((readl(timer_base +TCON )&~(0xf<<0)) | (0x2 <<0),timer_base +TCON );
}
void fs4412_beep_on(void)
{
writel ((readl(timer_base +TCON )&~(0xf<<0)) | (0x9 <<0),timer_base +TCON );
}
void fs4412_beep_off(void)
{
writel ((readl(timer_base +TCON )&~(0xf<<0)) | (0x0 <<0),timer_base +TCON );
}
static void beep_unmap(void)
{
iounmap(gpd0con);
iounmap(timer_base);
}
static int beep_open (struct inode *inode, struct file *filep)
{
fs4412_beep_on();
return 0;
}
static int beep_release(struct inode *inode, struct file *filep)
{
fs4412_beep_off();
return 0;
}
#define BEPP_IN_FREQ 100000
static void beep_freq(unsigned long arg)
{
writel(BEPP_IN_FREQ/arg, timer_base +TCNTB0 );
writel(BEPP_IN_FREQ/(2*arg), timer_base +TCMPB0 );
}
static long beep_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
{
switch(cmd)
{
case BEEP_ON:
fs4412_beep_on();
break;
case BEEP_OFF:
fs4412_beep_off();
break;
case BEEP_FREQ:
beep_freq( arg );
break;
default :
return -EINVAL;
}
return 0;
}
static struct file_operations beep_ops=
{
.open = beep_open,
.release = beep_release,
.unlocked_ioctl = beep_ioctl,
};
static int beep_probe(struct platform_device *pdev)
{
int ret;
printk("match ok!");
gpd0con = ioremap(pdev->resource[0].start,pdev->resource[0].end - pdev->resource[0].start);
timer_base = ioremap(pdev->resource[1].start, pdev->resource[1].end - pdev->resource[1].start);
devno = MKDEV(major,minor);
ret = register_chrdev(major,"beep",&beep_ops);
cls = class_create(THIS_MODULE, "myclass");
if(IS_ERR(cls))
{
unregister_chrdev(major,"beep");
return -EBUSY;
}
test_device = device_create(cls,NULL,devno,NULL,"beep");//mknod /dev/hello
if(IS_ERR(test_device))
{
class_destroy(cls);
unregister_chrdev(major,"beep");
return -EBUSY;
}
fs4412_beep_init();
return 0;
}
static int beep_remove(struct platform_device *pdev)
{
beep_unmap();
device_destroy(cls,devno);
class_destroy(cls);
unregister_chrdev(major,"beep");
return 0;
}
static struct platform_driver beep_driver=
{
.driver.name = "bigbang",
.probe = beep_probe,
.remove = beep_remove,
};
static int beep_init(void)
{
printk("beep_init");
return platform_driver_register(&beep_driver);
}
static void beep_exit(void)
{
printk("beep_exit");
platform_driver_unregister(&beep_driver);
return;
}
MODULE_LICENSE("GPL");
module_init(beep_init);
module_exit(beep_exit);
3、makefile
[cpp] view plain copy
ifneq ($(KERNELRELEASE),)
obj-m:=device.o driver.o
$(info "2nd")
else
#KDIR := /lib/modules/$(shell uname -r)/build
KDIR := /home/fs/linux/linux-3.14-fs4412
PWD:=$(shell pwd)
all:
$(info "1st")
make -C $(KDIR) M=$(PWD) modules
clean:
rm -f *.ko *.o *.symvers *.mod.c *.mod.o *.order
endif
4、test.c
[cpp] view plain copy
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
main()
{
int fd,i,lednum;
fd = open("/dev/beep",O_RDWR);
if(fd<0)
{
perror("open fail \n");
return ;
}
sleep(10);
close(fd);
}
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原文地址：https://www.cnblogs.com/big-devil/p/8590028.html