de2_switches.c

Altera DE2开发板的LED、LCD、SEG7和按键的linux下的设备驱动程序

/*  
	Copyright (C) 2007 Philipp Lutz

	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or 
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/
///////////////////////////////////////////////////////////////////////////////////////////////////
/*
Description:
------------
This device driver is capable of reading out the values of the switches found on the DE2 board.
It uses the major number SWITCHES_MAJOR to be able to create a corresponding device file to read from.
In uClinux for NIOS2 the automatic creation of device files is found in the script located at 
"vendors/Altera/nios2nommu/romfs_list".

In uClinux it works with the following command:
mknod /dev/switches 666 c 242 0

*/
////////////////////////////////////////////////////////////////////////////////////////////////////
//
// Debug defines:
// --------------
//
// uncomment following line to use the kernelmodule without
// io (inb / outb) functions, needed for debug purposses on host machine.
//#define TEST

// enables debug-kernel-messages (viewed via "dmesg" command)
//#define DEBUG
///////////////////////////////////////////////////////////////////////////////////////////////////

#include "de2_includes.h"

// major numbers for identifying the device files
#define SWITCHES_MAJOR		242

// base-adress mapping to device names according to linux-2.6.x/include/nios2_system.h
#define SWITCHES_BASE		na_Switch


// define buffers for the strings sended to user
char switches_string[STRING_LEN] = "0\0";
char* switches_ptr = switches_string;

// device files open?
int switches_is_open = 0;


/////////////////////////////////////////////////////////////////////////
// Open handler
/////////////////////////////////////////////////////////////////////////
static int switches_open(struct inode *inode, struct file *file)
{
#ifdef DEBUG
	printk("switches_open called\n");
#endif
	
	unsigned long int value = 0;
	np_pio *pio_switches  = (np_pio *)(SWITCHES_BASE);
	
	if (switches_is_open++) {
		printk("device busy...\n");
		return -EBUSY;
	}
	
	// get new information from register
#ifndef TEST
	value = inl(&pio_switches->np_piodata);
#endif
	ltoa(switches_string,value);

#ifdef DEBUG
	printk("read value: %i\n",value);
#endif
	
	switches_ptr = switches_string;

	try_module_get(THIS_MODULE);
	return 0;
}


/////////////////////////////////////////////////////////////////////////
// Release/Close handler
/////////////////////////////////////////////////////////////////////////
static int switches_release(struct inode *inode, struct file *file)
{
#ifdef DEBUG
	printk("switches_release called\n");
#endif
	--switches_is_open;		
	module_put(THIS_MODULE);
	return 0;
}


/////////////////////////////////////////////////////////////////////////
// Read handler
/////////////////////////////////////////////////////////////////////////
static ssize_t switches_read(struct file *filp, char *buffer, size_t length, loff_t * offset)
{
	// Number of bytes actually written to the buffer
	int bytes_read = 0;

#ifdef DEBUG
	printk("switches_read called\n");
#endif

	// If we're at the end of the message, return 0 signifying end of file
	if (*switches_ptr == 0)
		return 0;

	while (length-- && *switches_ptr) {
		/* The buffer is in the user data segment, not the kernel 
		segment so "*" assignment won't work.  We have to use 
		put_user which copies data from the kernel data segment to
		the user data segment. */
		put_user(*(switches_ptr++), buffer++);
		bytes_read++;
	}

#ifdef DEBUG
	printk("bytes read: %i\n",bytes_read);
#endif
	// return count of bytes, sent to user
	return bytes_read;
}


// definitions, which functions are called for /dev/switches
static struct file_operations fops_switches = 
{
	.read		= switches_read,
	.open		= switches_open,
	.release	= switches_release
};


/////////////////////////////////////////////////////////////////////////
// Init funktion
/////////////////////////////////////////////////////////////////////////
static int __init mod_init(void)
{
	np_pio *pio_switches = (np_pio *)(SWITCHES_BASE);

	// reserving memory regions for the I/O port
	if(!request_mem_region((unsigned long)SWITCHES_BASE, sizeof(np_pio), "de2_switches"))
		return -1;
	
	// registering PIO port as character device to the kernel
	if(register_chrdev(SWITCHES_MAJOR, "de2_switches", &fops_switches))
	{
		printk("register_chrdev of de2_switches failed!\n");
		release_mem_region((unsigned long)SWITCHES_BASE, sizeof(np_pio));
		return -EIO;
	}
	
#ifdef DEBUG
	printk("de2_switches registered successfully!\n");
#ifdef	TEST
	print("TEST mode active, so no I/O interaction is possible!\n");
#endif
#endif
	
	// set PIO port as input
#ifndef TEST
	outl(0, &pio_switches->np_piodirection);
#endif
	return 0;
}


/////////////////////////////////////////////////////////////////////////
// Exit function (will be spared if build-in device driver selected)
/////////////////////////////////////////////////////////////////////////
static void __exit mod_exit(void)
{
	// unregistering character device
	unregister_chrdev(SWITCHES_MAJOR,"de2_switches");

	// releasing memory region
	release_mem_region((unsigned long)SWITCHES_BASE, sizeof(np_pio));
}

// declaring the init/exit functions of the module
module_init( mod_init );
module_exit( mod_exit );
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Philipp Lutz");