Linux driver learning (2) - beep driver

// >0 sets the value in down_counter (beeping frequency)

//-------------------------------------------------------------

static int xiaoyang_beep_ioctl(struct inode *inode,        struct file *file,        unsigned int cmd,unsigned long arg)

{

unsigned long temp;

if(cmd <= 0)

{

//set as gpb0,output

temp = __raw_readl(S3C2410_GPBCON);        //GPBCON IO Control

temp &= ~3;        //just select the GPBCON[1:0]bits for gpb0

temp |= 1;        //set gpb[0] as output

__raw_writel(temp, S3C2410_GPBCON);

//set gpbdata[0](beep value) as 0

temp = __raw_readl(S3C2410_GPBDAT);        //GPBDAT

temp &= ~1;

__raw_writel(temp, S3C2410_GPBDAT);

}

else

{

//set as TOUT0

temp = __raw_readl(S3C2410_GPBCON);        //GPBCON

temp &= ~3;

temp |= 2;                //using TOUT0(pwm timer)

__raw_writel(temp, S3C2410_GPBCON);

//using pwm timer TOUT0

temp = __raw_readl(S3C2410_TCFG0);        //TCFG0

temp &= ~0xff;        //select Timer0

temp |= 15;                //FCLK/(15+1)/(devided value),prescaler value!

__raw_writel(temp, S3C2410_TCFG0);

temp = __raw_readl(S3C2410_TCFG1);        //TCFG1

temp &= ~0xf;        //select MUX0

temp |= 1;                //1/4 diveder

__raw_writel(temp, S3C2410_TCFG1);

//--------------------------------------------------------------

//        now set TCNTB and TCMPB,generate 1:1 diveded timer

//TCNTB register sets the initial value loaded into the down counter and decrements it in sequence

//TCMPB register is used to load the value to be compared with the down counter

// So when TCMPB = TCNTB/2 is set, it means 1:1 time division

//--------------------------------------------------------------

temp = (50000000/64)/cmd;//set timer count buffer rgister ,50MHZ/(16*4*cmd)

__raw_writel(temp, S3C2410_TCNTB(0));

temp >>= 1;

__raw_writel(temp, S3C2410_TCMPB(0));

//setup timer0

temp = __raw_readl(S3C2410_TCON); //TCON

temp &= ~0x1f;

temp |= 0xb;//disable deadzone,auto-reload,interval-off,update TCNTB and TCMPB,start timer0

__raw_writel(temp, S3C2410_TCON);

temp &= ~2;//set bit[0] as 0,clear manual update-setting bit

__raw_writel(temp, S3C2410_TCON);

}

return 0;

}

//--------------------------------------------------------------

// This structure is the core of the character device driver

// The open, read, write, ioctl and other functions called when the application operates the device file.

// The corresponding function specified in this structure will eventually be called

//--------------------------------------------------------------

static struct file_operations xiaoyang_beep_fops = {

.owner        =        THIS_MODULE,

.ioctl        =        xiaoyang_beep_ioctl,

};

static char __initdata banner[] = "TQ2440 Beep, 2010-xiaoyang yin";

static struct class *beep_class;

//--------------------------------------------------------------

// This function will be called when the "insmod xiaoyang_beep.ko" command is executed

//--------------------------------------------------------------

static int __init xiaoyang_beep_init(void)

{

int ret;

printk(banner);

//--------------------------------------------------------------

// Register character device driver

// The parameters are the main device number, device name, and file_operations structure;

// In this way, the major device number is associated with the specific file_operations structure,

// When operating a device file whose main device is BEEP_MAJOR, the relevant member function in xiaoyang_beep_fops will be called

// BEEP_MAJOR can be set to 0, indicating that the kernel automatically assigns the major device number

//--------------------------------------------------------------

ret = register_chrdev(BEEP_MAJOR, DEVICE_NAME, &xiaoyang_beep_fops);//Assign device number

if (ret < 0) {

printk(DEVICE_NAME " can't register major numbern");

return ret;

}

//Register a class so that mdev can create device nodes under the "/dev/" directory

beep_class = class_create(THIS_MODULE, DEVICE_NAME);

if(IS_ERR(beep_class))

{

printk("Err: failed in xiaoyang-Beep class. n");

return -1;

}

//Create a device node named DEVICE_NAME

device_create(beep_class, NULL, MKDEV(BEEP_MAJOR, 0), NULL, DEVICE_NAME);

printk(DEVICE_NAME " initializedn");

return 0;

}

//--------------------------------------------------------------

// This function will be called when the "rmmod xiaoyang_beep.ko" command is executed

//--------------------------------------------------------------

static void __exit xiaoyang_beep_exit(void)

{

/* Uninstall the driver */

unregister_chrdev(BEEP_MAJOR, DEVICE_NAME);

device_destroy(beep_class, MKDEV(BEEP_MAJOR, 0)); //Delete the device node

class_destroy(beep_class); //Deregister class

}

//Specify the driver's initialization function and uninstallation function

module_init(xiaoyang_beep_init);

module_exit(xiaoyang_beep_exit);

/* Describe some information about the driver, not required */

MODULE_AUTHOR("software-hit"); //Driver author

MODULE_DESCRIPTION("TQ2440 Beep Driver"); //Description information

MODULE_LICENSE("GPL"); //Agreement to follow

Add it to the kernel, configure drivers/char/Kconfig and Makefile, copy config_EmbededSky_W35 in the root directory to .config and run: Make menuconfig to configure.

Beep can be added to the kernel as a module or as a mandatory part of the kernel. Then run

Make oldconfig

Make

After generating zImage and burning it to the development board, there will be a /dev/beep device.

If you want to compile it as a module, just run Make SUBDIR=drivers/char/modules to compile EmbededSky_Beep.ko, copy it to the development board and load it with insmod.

The following problems occurred during the compilation process:

drivers/char/EmbedSky_beep.c: In function 'xiaoyang_beep_init':

drivers/char/EmbedSky_beep.c:134: error: implicit declaration of function 'class_device_create'

drivers/char/EmbedSky_beep.c: In function 'xiaoyang_beep_exit':

drivers/char/EmbedSky_beep.c:148: error: implicit declaration of function 'class_device_destroy'

make[2]: *** [drivers/char/EmbedSky_beep.o] Error 1

make[1]: *** [drivers/char] Error 2

make: *** [drivers] Error 2

[xiaoyang@localhost linux-2.6.3

Solution:

This is mainly caused by interface changes between versions.

In Linux 2.6, there are some modifications in different versions to address the above problem. Before using, you should first check the function declaration in /.../include/linux/device.h. For example, if I use Linux 2.6.30, there is no class_device_create function, and you can directly use device_create. In previous versions such as Linux 2.6.15, you need to use the class_device_create function.

So don't use class_device_create but use device_create instead, and the same goes for the other interface.

Writing an application:

//----------------------------------------------------------

// xiaoyang@2011.4.21

// beep driver/module test

//----------------------------------------------------------

#include

#include

#include

#include

#include

#include

int main()

{

int fd;

int i = 0;

int m_pwm_val;

fd = open("/dev/xiaoyang-beep",O_RDWR);

if(fd < 0){

perror("open device xiaoyang-beep error!");

exit(1);

}

for(i = 0; i < 1000; i++){

scanf("%d",&m_pwm_val);

printf("your pwm_val is %dn",m_pwm_val);

ioctl(fd,m_pwm_val,4); //The last parameter is useless. ioctl: Linux interface uses a unified interface to operate the device

if(m_pwm_val == 0){

break;

}

}

close(fd);

return 0;

}

Makefile is as follows:

CROSS_COMPILE=arm-linux-

CC=$(CROSS_COMPILE)gcc

obj-m := hello.o

all:beep

beep:beep.c

$(CC) -o beep beep.c

$(CROSS_COMPILE)strip beep

clean:

rm -rf *.o beep

Screenshot of experimental results:

After entering the number, the beep sounds at different frequencies, which is too harsh.