How to call ioctl function

[pnpvivek]

hai friend,
I have a doubt in ioctl function..The function is
int device_ioctl(struct inode *inode,struct file *file,unsigned int ioctl_num,unsigned long ioctl_param)......
when its called in our program and what purpose it is used and also give me a detail about ioctl function with an simple example..

Thanks in advance..
vivek

[ashok449]

// user space program for ioctl

#define CDROMEJECT 1
int main (int argc, char* argv[])
{
/* Open a file descriptor to the device specified on the command line. */
int fd = open (argv[1], O_RDONLY); //argv[1] is /dev/cdrom
/* Eject the CD-ROM. */
ioctl (fd, CDROMEJECT); /*CDROMEJECT become device_ioctl.. int cmd parameter */
/* Close the file descriptor. */
close (fd);
return 0;
}

device driver ioctl

static int device_ioctl(struct inode *inode, struct file *filp, unsigned int cmd, unsigned long arg)
{

switch(cmd)
{
case CDROMEJECT:
printk("CD-ROM EJECTED\n");
break;
default:
printk("IOCTL DEFAULT COMMAND EXECUTED\n");
}

return 0;
}

hope this helps you

Ashok Athukuri

[garimaanurag]

Hi above,

I tried your sample user space application but it didn't work for me.
i compiled successfully the userapp and ran in tha way as:

./a.out /dev/cdrom
but after hitting enter nothing happened.
I want to see the practical example of ioctl like this e.g. but it's not working can you tell waht is problem?

I am using ubuntu9.10 ang gcc4.4.1