驅(qū)動(dòng)之路之platform按鍵驅(qū)動(dòng)

一、重要知識(shí)點(diǎn)：

從Linux 2.6起引入了一套新的驅(qū)動(dòng)管理和注冊(cè)機(jī)制，platform_device和platform_driver,Linux中大部分的設(shè)備驅(qū)動(dòng)都可以使用這套機(jī)制。platform是一條虛擬的總線。設(shè)備用platform_device表示，驅(qū)動(dòng)用platform_driver進(jìn)行注冊(cè)，Linux platform driver機(jī)制和傳統(tǒng)的device driver機(jī)制（通過driver_register進(jìn)行注冊(cè)）相比，一個(gè)明顯的優(yōu)勢(shì)在于platform機(jī)制將設(shè)備本身的資源注冊(cè)進(jìn)內(nèi)核，由內(nèi)核統(tǒng)一管理，在驅(qū)動(dòng)中使用這些資源時(shí)通過platform device提供的標(biāo)準(zhǔn)結(jié)構(gòu)進(jìn)行申請(qǐng)并使用。這樣提高了驅(qū)動(dòng)和資源的獨(dú)立性，并且具有較好的可移植性和安全性（這些標(biāo)準(zhǔn)接口是安全的）。

pltform機(jī)制本身使用并不復(fù)雜，由兩部分組成：platform_device和platform_driver。通過platform機(jī)制開發(fā)底層驅(qū)動(dòng)的大致流程為：定義platform_deive->注冊(cè)platform_device->定義platform_driver->注冊(cè)platform_driver。

首先要確認(rèn)的就是設(shè)備的資源信息，例如設(shè)備的地址，中斷號(hào)等。

在 2.6 內(nèi)核中 platform 設(shè)備用結(jié)構(gòu)體 platform_device 來描述，該結(jié)構(gòu)體定義在 kernel/include/linux/platform_device.h 中，

structplatform_device {

const char * name;

u32? id;

struct device dev;

u32? num_resources;

struct resource * resource;

};

該結(jié)構(gòu)一個(gè)重要的元素是resource ，該元素存入了最為重要的設(shè)備資源信息，定義在kernel/include/linux/ioport.h 中，

structresource {

const char *name;//資源的名稱

unsigned long start, end;//資源起始的和結(jié)束的物理地址

unsigned long flags;//資源的類型，比如MEM,IO,IRQ類型

struct resource *parent, *sibling, *child;//資源鏈表的指針

};

structplatform_device的分配使用

structplatform_device *platform_device_alloc(const char *name, int id)

name是設(shè)備名，id，設(shè)備id，一般為-1，如果是-1，表示同樣名字的設(shè)備只有一個(gè)

舉個(gè)簡(jiǎn)單的例子，name/id是“serial/1”則它的bus_id就是serial.1? 如果name/id是“serial/0”則它的bus_id就是serial.0 ,如果它的name/id是“serial/-1”則它的bus_id就是serial。

注冊(cè)平臺(tái)設(shè)備，使用函數(shù)

intplatform_device_add(struct platform_device *pdev)

注銷使用

voidplatform_device_unregister(struct platform_device *pdev)

在平臺(tái)設(shè)備驅(qū)動(dòng)中獲取平臺(tái)設(shè)備資源使用

structresource *platform_get_resource(struct platform_device *dev, unsigned int type,unsigned int num)

該函數(shù)用于獲取dev設(shè)備的第num個(gè)類型為type的資源，如果獲取失敗，則返回NULL。例如 platform_get_resource(pdev,IORESOURCE_IRQ, 0)。

平臺(tái)驅(qū)動(dòng)描述使用

structplatform_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()函數(shù)必須驗(yàn)證指定設(shè)備的硬件是否真的存在，probe()可以使用設(shè)備的資源，包括時(shí)鐘，platform_data等，Platform driver可以通過下面的函數(shù)完成對(duì)驅(qū)動(dòng)的注冊(cè)：

int platform_driver_register(structplatform_driver *drv);一般來說設(shè)備是不能被熱插拔的，所以可以將probe()函數(shù)放在init段里面來節(jié)省driver運(yùn)行時(shí)候的內(nèi)存開銷：

int platform_driver_probe(struct platform_driver *drv, int (*probe)(structplatform_device *))；

注銷使用void platform_driver_unregister(struct platform_driver *drv)

2.中斷處理

在Linux驅(qū)動(dòng)程序中，為設(shè)備實(shí)現(xiàn)一個(gè)中斷包含兩個(gè)步驟1.向內(nèi)核注冊(cè)（申請(qǐng)中斷）中斷 2.實(shí)現(xiàn)中斷處理函數(shù)

request_irq用于實(shí)現(xiàn)中斷的注冊(cè)

intrequest_irq(unsigned in irq, void(*handler)(int, void *， struct pt_regs *), unsigned long flags, const char *devname, void*dev_id)

向內(nèi)核申請(qǐng)中斷號(hào)為irq，中斷處理函數(shù)為handler指針指向的函數(shù)，中斷標(biāo)志為flag，設(shè)備名為devname的中斷。成功返回0，或者返回一個(gè)錯(cuò)誤碼。

當(dāng)request_irq不用于共享中斷時(shí)，dev_id可以為NULL，或者指向驅(qū)動(dòng)程序自己的私有數(shù)據(jù)。但用于共享中斷時(shí)dev_id必須唯一。因?yàn)閒ree_irq時(shí)也需要dev_id做參數(shù)，這樣free_irq才知道要卸載共享中斷上哪個(gè)中斷服務(wù)處理函數(shù)。共享中斷會(huì)在后面講到。

在flag參數(shù)中，可以選以下參數(shù)

IRQF_DISABLED(SA_INTERRUPT)

如果設(shè)置該位，表示是一個(gè)“快速”中斷處理程序，如果沒有，那么就是一個(gè)“慢速”中斷處理程序。

IRQF_SHARED(SA_SHITQ)

該位表示中斷可以在設(shè)備間共享。

快速/慢速中斷

這兩種類型的中斷處理程序的主要區(qū)別在于：快速中斷保證中斷處理的原子性（不被打斷），而慢速中斷則不保證。換句話說，也就是開啟中斷標(biāo)志位在運(yùn)行快速中斷處理程序時(shí)

關(guān)閉的，因此在服務(wù)該中斷時(shí)，不會(huì)被其他類型的中斷打斷；而調(diào)用慢速中斷處理時(shí)，其他類型中斷扔可以得到服務(wù)。

共享中斷

共享中斷就是將不同的設(shè)備掛到同一個(gè)中斷信號(hào)線上。linux對(duì)共享的支持主要是位PCI設(shè)備服務(wù)。

釋放中斷

voidfree_irq(unsigned int irq)

當(dāng)設(shè)備不再需要使用中斷時(shí)（通常是設(shè)備關(guān)閉和驅(qū)動(dòng)卸載時(shí)），應(yīng)該使用該函數(shù)把他們返回給內(nèi)核使用。

禁用中斷

voiddisable_irq(int irq)

當(dāng)一些代碼中不能使用中斷時(shí)（如支持自旋鎖的上下文中）使用該函數(shù)禁用中斷。

啟用中斷

voidenable_irq(int irq)

當(dāng)禁止后可以使用該函數(shù)重新啟用。

二、驅(qū)動(dòng)代碼

該驅(qū)動(dòng)實(shí)現(xiàn)能夠讀取按鍵按下的鍵值，比如說如果是第一個(gè)鍵按下讀取的鍵值就為1。

platform平臺(tái)設(shè)備

#include???

static?struct?resource?key_resource[]=??

{?????

[0]?=?{??

.start?=?IRQ_EINT8,??

.end?=?IRQ_EINT8,??

.flags?=?IORESOURCE_IRQ,??

},??

[1]?=?{??

.start?=?IRQ_EINT11,??

.end?=?IRQ_EINT11,??

.flags?=?IORESOURCE_IRQ,??

},??

[2]=?{??

.start?=?IRQ_EINT13,??

.end?=?IRQ_EINT13,??

.flags?=?IORESOURCE_IRQ,??

},??

[3]?=?{??

.start?=?IRQ_EINT14,??

.end?=?IRQ_EINT14,??

.flags?=?IORESOURCE_IRQ,??

},??

[4]?=?{??

.start?=?IRQ_EINT15,??

.end?=?IRQ_EINT15,??

.flags?=?IORESOURCE_IRQ,??

},??

[5]?=?{??

.start?=?IRQ_EINT19,??

.end?=?IRQ_EINT19,??

.flags?=?IORESOURCE_IRQ,??

},??

};??

struct?platform_device?*my_buttons_dev;??

static?int?__init?platform_dev_init(void)??

{??

int?ret;??

my_buttons_dev?=?platform_device_alloc("my_buttons",?-1);??

platform_device_add_resources(my_buttons_dev,key_resource,6);//添加資源一定要用該函數(shù)，不能使用對(duì)platform_device->resource幅值??

//否則會(huì)導(dǎo)致platform_device_unregister調(diào)用失敗，內(nèi)核異常。??

ret?=?platform_device_add(my_buttons_dev);??

if(ret)??

platform_device_put(my_buttons_dev);??

return?ret;??

}??

static?void?__exit?platform_dev_exit(void)??

{??

platform_device_unregister(my_buttons_dev);??

}??

module_init(platform_dev_init);??

module_exit(platform_dev_exit);??

MODULE_AUTHOR("Y-Kee");??

MODULE_LICENSE("GPL");??

#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include static struct resource key_resource[]={[0] = {.start = IRQ_EINT8,.end = IRQ_EINT8,.flags = IORESOURCE_IRQ,},[1] = {.start = IRQ_EINT11,.end = IRQ_EINT11,.flags = IORESOURCE_IRQ,},[2]= {.start = IRQ_EINT13,.end = IRQ_EINT13,.flags = IORESOURCE_IRQ,},[3] = {.start = IRQ_EINT14,.end = IRQ_EINT14,.flags = IORESOURCE_IRQ,},[4] = {.start = IRQ_EINT15,.end = IRQ_EINT15,.flags = IORESOURCE_IRQ,},[5] = {.start = IRQ_EINT19,.end = IRQ_EINT19,.flags = IORESOURCE_IRQ,},};struct platform_device *my_buttons_dev;static int __init platform_dev_init(void){int ret;my_buttons_dev = platform_device_alloc("my_buttons", -1);platform_device_add_resources(my_buttons_dev,key_resource,6);//添加資源一定要用該函數(shù)，不能使用對(duì)platform_device->resource幅值//否則會(huì)導(dǎo)致platform_device_unregister調(diào)用失敗，內(nèi)核異常。ret = platform_device_add(my_buttons_dev);if(ret)platform_device_put(my_buttons_dev);return ret;}static void __exit platform_dev_exit(void){platform_device_unregister(my_buttons_dev);}module_init(platform_dev_init);module_exit(platform_dev_exit);MODULE_AUTHOR("Y-Kee");MODULE_LICENSE("GPL");
?

platform平臺(tái)驅(qū)動(dòng)

//platform?driver??

#include???

static?int?buttons_irq[6];??

struct?irq_des??

{??

int?*buttons_irq;??

char?*name[6];??

};??

struct?irq_des?button_irqs?=?{???

.buttons_irq?=?buttons_irq,??

.name?=?{"KEY0",?"KEY1",?"KEY2",?"KEY3",?"KEY4",?"KEY5"},??

};??

static?volatile?int?key_values;??

static?DECLARE_WAIT_QUEUE_HEAD(button_waitq);??

static?volatile?int?ev_press?=?0;??

static?irqreturn_t?buttons_interrupt(int?irq,?void?*dev_id)??

{??

int?i;??

for(i=0;?i<6;?i++){??

if(irq?==?buttons_irq[i]){??

key_values?=?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;??

for?(i?=?0;?i?

err?=?request_irq(button_irqs.buttons_irq[i],?buttons_interrupt,?IRQ_TYPE_EDGE_BOTH,???

button_irqs.name[i],?(void?*)&button_irqs.buttons_irq[i]);??

if?(err)??

break;??

}??

if?(err)?{??

i--;??

for?(;?i?>=?0;?i--)?{??

if?(button_irqs.buttons_irq[i]?

continue;??

}??

disable_irq(button_irqs.buttons_irq[i]);??

free_irq(button_irqs.buttons_irq[i],?(void?*)&button_irqs.buttons_irq[i]);??

}??

return?-EBUSY;??

}??

return?0;??

}??

static?int?s3c24xx_buttons_close(struct?inode?*inode,?struct?file?*file)??

{??

int?i;??

for?(i?=?0;?i?

free_irq(button_irqs.buttons_irq[i],?(void?*)&button_irqs.buttons_irq[i]);??

}??

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;??

else??

wait_event_interruptible(button_waitq,?ev_press);??

}??

ev_press?=?0;??

err?=?copy_to_user(buff,?(const?void?*)&key_values,?min(sizeof(key_values),?count));??

return?err???-EFAULT?:?min(sizeof(key_values),?count);??

}??

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?dev_fops?=?{??

.owner???=???THIS_MODULE,??

.open????=???s3c24xx_buttons_open,??

.release?=???s3c24xx_buttons_close,???

.read????=???s3c24xx_buttons_read,??

.poll????=???s3c24xx_buttons_poll,??

};??

static?struct?miscdevice?misc?=?{??

.minor?=?MISC_DYNAMIC_MINOR,??

.name?=?"my_buttons",??

.fops?=?&dev_fops,??

};??

static?int?my_plat_probe(struct?platform_device?*dev)??

{??

int?ret,i;??

struct?resource?*plat_resource;??

struct?platform_device?*pdev?=?dev;??

printk("my?platform?dirver?find?my?platfrom?device.\n");??

for(i=0;?i<6;?i++){??

plat_resource?=?platform_get_resource(pdev,IORESOURCE_IRQ,i);??

if(plat_resource?==?NULL)??

return?-ENOENT;???

buttons_irq[i]?=?plat_resource->start;??

}??

ret?=?misc_register(&misc);??

if(ret)??

return?ret;??

return?0;??

}??

static?int?my_plat_remove(struct?platform_device?*dev)??

{??

printk("my?platfrom?device?has?removed.\n");??

misc_deregister(&misc);??

return?0;??

}??

struct?platform_driver?my_buttons_drv?=?{???

.probe?=?my_plat_probe,??

.remove?=?my_plat_remove,??

.driver?=?{???

.owner?=?THIS_MODULE,??

.name?=?"my_buttons",??

},??

};??

static?int?__init?platform_drv_init(void)??

{??

int?ret;??

ret?=?platform_driver_register(&my_buttons_drv);??

return?ret;??

}??

static?void?__exit?platform_drv_exit(void)??

{??

platform_driver_unregister(&my_buttons_drv);??

}??

module_init(platform_drv_init);??

module_exit(platform_drv_exit);??

MODULE_AUTHOR("Y-Kee");??

MODULE_LICENSE("GPL");??

//platform driver#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include static int buttons_irq[6];struct irq_des{int *buttons_irq;char *name[6];};struct irq_des button_irqs = {.buttons_irq = buttons_irq,.name = {"KEY0", "KEY1", "KEY2", "KEY3", "KEY4", "KEY5"},};static volatile int key_values;static DECLARE_WAIT_QUEUE_HEAD(button_waitq);static volatile int ev_press = 0;static irqreturn_t buttons_interrupt(int irq, void *dev_id){int i;for(i=0; i<6; i++){if(irq == buttons_irq[i]){key_values = 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;for (i = 0; i < 6; i++) {err = request_irq(button_irqs.buttons_irq[i], buttons_interrupt, IRQ_TYPE_EDGE_BOTH,button_irqs.name[i], (void *)&button_irqs.buttons_irq[i]);if (err)break;}if (err) {i--;for (; i >= 0; i--) {if (button_irqs.buttons_irq[i] < 0) {continue;}disable_irq(button_irqs.buttons_irq[i]);free_irq(button_irqs.buttons_irq[i], (void *)&button_irqs.buttons_irq[i]);}return -EBUSY;}return 0;}static int s3c24xx_buttons_close(struct inode *inode, struct file *file){int i;for (i = 0; i < 6; i++) {free_irq(button_irqs.buttons_irq[i], (void *)&button_irqs.buttons_irq[i]);}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, (const void *)&key_values, min(sizeof(key_values), count));return err ? -EFAULT : min(sizeof(key_values), count);}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 dev_fops = {.owner = THIS_MODULE,.open = s3c24xx_buttons_open,.release = s3c24xx_buttons_close,.read = s3c24xx_buttons_read,.poll = s3c24xx_buttons_poll,};static struct miscdevice misc = {.minor = MISC_DYNAMIC_MINOR,.name = "my_buttons",.fops = &dev_fops,};static int my_plat_probe(struct platform_device *dev){int ret,i;struct resource *plat_resource;struct platform_device *pdev = dev;printk("my platform dirver find my platfrom device.\n");for(i=0; i<6; i++){plat_resource = platform_get_resource(pdev,IORESOURCE_IRQ,i);if(plat_resource == NULL)return -ENOENT;buttons_irq[i] = plat_resource->start;}ret = misc_register(&misc);if(ret)return ret;return 0;}static int my_plat_remove(struct platform_device *dev){printk("my platfrom device has removed.\n");misc_deregister(&misc);return 0;}struct platform_driver my_buttons_drv = {.probe = my_plat_probe,.remove = my_plat_remove,.driver = {.owner = THIS_MODULE,.name = "my_buttons",},};static int __init platform_drv_init(void){int ret;ret = platform_driver_register(&my_buttons_drv);return ret;}static void __exit platform_drv_exit(void){platform_driver_unregister(&my_buttons_drv);}module_init(platform_drv_init);module_exit(platform_drv_exit);MODULE_AUTHOR("Y-Kee");MODULE_LICENSE("GPL");

/*??

*??????Buttons?Example?for?Matrix?V??

*??

*??capbily@hotmail.com??

*/??

#include???

int?main(void)??

{??

int?buttons_fd;??

int?key_value;??

buttons_fd?=?open("/dev/buttons",?0);??

if?(buttons_fd?

perror("open?device?buttons");??

exit(1);??

}??

for?(;;)?{??

fd_set?rds;??

int?ret;??

FD_ZERO(&rds);??

FD_SET(buttons_fd,?&rds);??

ret?=?select(buttons_fd?+?1,?&rds,?NULL,?NULL,?NULL);??

if?(ret?

perror("select");??

exit(1);??

}??

if?(ret?==?0)?{??

printf("Timeout.\n");??

}?else?if?(FD_ISSET(buttons_fd,?&rds))?{??

int?ret?=?read(buttons_fd,?&key_value,?sizeof?key_value);??

if?(ret?!=?sizeof?key_value)?{??

if?(errno?!=?EAGAIN)??

perror("read?buttons\n");??

continue;??

}?else?{??

printf("buttons_value:?%d\n",?key_value+1);??

}??

close(buttons_fd);??

return?0;??

}??

/** Buttons Example for Matrix V** Copyright (C) 2004 capbily - friendly-arm*capbily@hotmail.com*/#include #include #include #include #include #include #include #include #include #include int main(void){int buttons_fd;int key_value;buttons_fd = open("/dev/buttons", 0);if (buttons_fd < 0) {perror("open device buttons");exit(1);}for (;;) {fd_set rds;int ret;FD_ZERO(&rds);FD_SET(buttons_fd, &rds);ret = select(buttons_fd + 1, &rds, NULL, NULL, NULL);if (ret < 0) {perror("select");exit(1);}if (ret == 0) {printf("Timeout.\n");} else if (FD_ISSET(buttons_fd, &rds)) {int ret = read(buttons_fd, &key_value, sizeof key_value);if (ret != sizeof key_value) {if (errno != EAGAIN)perror("read buttons\n");continue;} else {printf("buttons_value: %d\n", key_value+1);}}}close(buttons_fd);return 0;}