Linux Platform Device and Driver(以I2C为例)

/* arch/arm/mach-s3c2410/devs.c */

/* I2C */

static struct resource s3c_i2c_resource[]
= {

[ 0]=
{

. start
= S3C24XX_PA_IIC,

. end
= S3C24XX_PA_IIC + S3C24XX_SZ_IIC
- 1,

. flags
= IORESOURCE_MEM,

} ,

[ 1]=
{

. start
= IRQ_IIC,
//S3C2410_IRQ(27)

. end
= IRQ_IIC,

. flags
= IORESOURCE_IRQ,

}

} ;

struct platform_device s3c_device_i2c=
{

. name ="s3c2410-i2c"
,

. id =- 1,

. num_resources
= ARRAY_SIZE( s3c_i2c_resource),

. resource
= s3c_i2c_resource,

} ;

/* arch/arm/mach-3sc2410/cpu.c */

static int __init s3c_arch_init(void
)

{

int ret;

……

/* 这里board指针指向在mach-smdk2410.c里的定义的smdk2410_board，里面包含了预先定义的I2C Platform_device等. */

if (
board ! =NULL
) {

struct platform_device
* * ptr = board-> devices;

int i;

for ( i= 0; i
< board-
> devices_count; i++
, ptr++
) {

ret =
platform_device_register(
* ptr) ;
//在这里进行注册

if ( ret){

printk( KERN_ERR
"s3c24xx: failed to add board device %s (%d) @%p/n"
, ( * ptr)-
> name,

ret, * ptr);

}

}

/* mask any error, we may not need all these board

* devices */

ret = 0;

}

return ret;

}

/* device driver for platform bus bits */

static
struct platform_driver s3c2410_i2c_driver ={

. probe = s3c24xx_i2c_probe,

. remove= s3c24xx_i2c_remove,

. resume
= s3c24xx_i2c_resume,

. driver
= {

. owner
= THIS_MODULE,

. name
= "s3c2410-i2c"
,

} ,

} ;

/* drivers/i2c/busses/i2c-s3c2410.c */

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,/* 申请IRQ */

pdev- > name, i2c);

……

return ret;

}