//-------------------------------------------------------------------
//	updown.c
//
//	This module's 'get_info()' function shows how to acquire and
//	release the kernel's 'ide_cfg_sem' semaphore on workstations
//	in the USF Kudlick Classroom and Fifth-Floor of Harney labs.
//	The kernel-address of this semaphore is hard-coded here, and
//	was derived from information in the (uncompressed) 'vmlinux'
//	kernel binary using this command-sequence:
//
//	  	$ cd /usr/src/linux
//	  	$ objdump -t vmlinux | grep ide_cfg_sem 
//
//	NOTE: Developed and tested with Linux kernel version 2.6.10.
//
//	programmer: ALLAN CRUSE
//	written on: 14 MAR 2005
//-------------------------------------------------------------------

#include <linux/module.h>	// for init_module() 
#include <linux/proc_fs.h>	// for create_proc_info_entry() 

char modname[] = "updown";
struct semaphore *semp = (struct semaphore *)0xC02BBDC0; // USF only!

int my_get_info( char *buf, char **start, off_t off, int count )
{
	int	len = 0;

	len += sprintf( buf+len, "ide_cfg_sem.count=%d\n", 
			semp->count.counter );

	down_interruptible( semp );	// <--- acquire the semaphore

	len += sprintf( buf+len, "ide_cfg_sem.count=%d\n", 
			semp->count.counter );

	up( semp );			// <--- release the semaphore

	len += sprintf( buf+len, "ide_cfg_sem.count=%d\n", 
			semp->count.counter );
	return	len;
}

int init_module( void )
{
	printk( "<1>\nInstalling \'%s\' module\n", modname );
	create_proc_info_entry( modname, 0, NULL, my_get_info );
	return	0;  //SUCCESS
}

void cleanup_module( void )
{
	remove_proc_entry( modname, NULL );
	printk( "<1>Removing \'%s\' module\n", modname );
}

MODULE_LICENSE("GPL");