/*======================================================================
A Globalmem Driver As an example of char device drivers
There are two same globalmems in this driver
This example was to introduce the function of File->private_data
The initial developer of the original code is Baohua Song
<author@linuxdriver.cn>. All Rights Reserved.
======================================================================*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <asm/io.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#define GLOBALMEM_SIZE 0x1000/* Global Memory Maximum 4K bytes */
#define MEM_CLEAR 0x1/* Clear 0 global Memory * *
#define GLOBALMEM_MAJOR 254/* Preset GLOBALMEM main device number * *
static unsigned int globalmem_major = globalmem_major;
/*GLOBALMEM Equipment Structure Body * *
struct GLOBALMEM_DEV
{
struct Cdev Cdev; /*CDEV Structure Body * *
unsigned char mem[globalmem_size]; /* Global Memory * *
};
struct Globalmem_dev *globalmem_devp; /* Device Structure body pointer * *
/* File Open function/*
int Globalmem_open (struct inode *inode, struct file *filp)
{
/* Assign the device structure pointer to the file private data pointer.
struct Globalmem_dev *dev;
dev = container_of (inode->i_cdev,struct globalmem_dev,cdev);
Filp->private_data = Dev;
return 0;
}
/* File Release function/*
int globalmem_release (struct inode *inode, struct file *filp)
{
return 0;
}
/* IOCTL Device control function * *
static int globalmem_ioctl (struct inode *inodep, struct file *filp, unsigned
int cmd, unsigned long arg)
{
struct Globalmem_dev *dev = filp->private_data;/* Obtain the device structure body pointer */
Switch (CMD)
{
Case Mem_clear:
memset (dev->mem, 0, globalmem_size);
PRINTK (kern_info "Globalmem is set to zero\n");
Break
Default
Return-einval;
}
return 0;
}
/* Read function * *
Static ssize_t globalmem_read (struct file *filp, char __user *buf, size_t size,
loff_t *ppos)
{
unsigned long p = *ppos;
unsigned int count = size;
int ret = 0;
struct Globalmem_dev *dev = filp->private_data; /* Get the device structure body pointer/*
/* Analyze and obtain valid write length * *
if (P >= globalmem_size)
return count? -enxio:0;
if (Count > Globalmem_size-p)
Count = globalmem_size-p;
/* Kernel space-> User space * *
if (Copy_to_user (buf, (void*) (Dev->mem + P), count)
{
ret =-Efault;
}
Else
{
*ppos + = count;
ret = count;
PRINTK (kern_info "read%d bytes (s) from%lu\n", Count, p);
}
return ret;
}
/* Write function * *
Static ssize_t globalmem_write (struct file *filp, const char __user *buf,
size_t size, loff_t *ppos)
{
unsigned long p = *ppos;
unsigned int count = size;
int ret = 0;
struct Globalmem_dev *dev = filp->private_data; /* Get the device structure body pointer/*
/* Analyze and obtain valid write length * *
if (P >= globalmem_size)
return count? -enxio:0;
if (Count > Globalmem_size-p)
Count = globalmem_size-p;
/* User space-> kernel space * *
if (Copy_from_user (Dev->mem + p, buf, Count))
ret =-Efault;
Else
{
*ppos + = count;
ret = count;
PRINTK (kern_info "written%d bytes (s) from%lu\n", Count, p);
}
return ret;
}
/* Seek file positioning function * *
Static loff_t globalmem_llseek (struct file *filp, loff_t offset, int orig)
{
loff_t ret = 0;
Switch (orig)
{
Case 0:/* Relative to file start position offset *
if (Offset < 0)
{
ret =-einval;
Break
}
if ((unsigned int) offset > globalmem_size)
{
ret =-einval;
Break
}
Filp->f_pos = (unsigned int) offset;
RET = filp->f_pos;
Break
Case 1:/* Relative file Current position offset */
if ((Filp->f_pos + offset) > Globalmem_size)
{
ret =-einval;
Break
}
if ((Filp->f_pos + offset) < 0)
{
ret =-einval;
Break
}
Filp->f_pos + = offset;
RET = filp->f_pos;
Break
Default
ret =-einval;
Break
}
return ret;
}
/* File operation structure Body * *
static const struct File_operations Globalmem_fops =
{
. Owner = This_module,
. Llseek = Globalmem_llseek,
. Read = Globalmem_read,
. write = Globalmem_write,
. IOCTL = Globalmem_ioctl,
. open = Globalmem_open,
. Release = Globalmem_release,
};
/* Initialize and register cdev*/
static void Globalmem_setup_cdev (struct globalmem_dev *dev, int index)
{
int err, Devno = Mkdev (globalmem_major, index);
Cdev_init (&dev->cdev, &globalmem_fops);
Dev->cdev.owner = This_module;
Dev->cdev.ops = &globalmem_fops;
Err = Cdev_add (&dev->cdev, Devno, 1);
if (ERR)
PRINTK (kern_notice "Error%d adding led%d", err, index);
}
/* Device driver Module loading function * *
int globalmem_init (void)
{
int result;
dev_t Devno = Mkdev (globalmem_major, 0);
/* Apply for equipment number * *
if (globalmem_major)
result = Register_chrdev_region (Devno, 2, "Globalmem");
else/* Dynamic Request device Number * *
{
result = Alloc_chrdev_region (&devno, 0, 2, "Globalmem");
Globalmem_major = Major (Devno);
}
if (Result < 0)
return result;
/* Dynamic request 2 device Structure of memory * *
GLOBALMEM_DEVP = Kmalloc (2*sizeof (struct Globalmem_dev), gfp_kernel);
if (!GLOBALMEM_DEVP)/* Request failed * *
{
result =-Enomem;
Goto Fail_malloc;
}
memset (GLOBALMEM_DEVP, 0, 2*sizeof (struct globalmem_dev));
Globalmem_setup_cdev (&globalmem_devp[0], 0);
Globalmem_setup_cdev (&globalmem_devp[1], 1);
return 0;
Fail_malloc:unregister_chrdev_region (Devno, 1);
return result;
}
/* Module Unload function * *
void Globalmem_exit (void)
{
PRINTK (kern_info "Good bye,mem!\n");
Cdev_del (& (Globalmem_devp[0].cdev));
Cdev_del (& (Globalmem_devp[1].cdev)); /* Logoff cdev*/
Kfree (GLOBALMEM_DEVP); /* release device structure inside the deposit * *
Unregister_chrdev_region (Mkdev (globalmem_major, 0), 2); /* Release Device number * *
}
Module_author ("Song Baohua");
Module_license ("Dual BSD/GPL");
Module_param (globalmem_major, int, s_irugo);
Module_init (Globalmem_init);
Module_exit (Globalmem_exit);
