fsc_device.c File Reference

FS Char Device settings, implementation. More...

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/version.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/statfs.h>
#include <linux/mm.h>
#include <asm/uaccess.h>
#include <asm/errno.h>
#include <linux/buffer_head.h>
#include <linux/pagemap.h>
#include <linux/proc_fs.h>
#include <asm/atomic.h>
#include "fsc_debug.h"
#include "fsc_device.h"

Go to the source code of this file.

Functions
	module_param (fsc_major, int, S_IRUSR)
ssize_t	fsc_read (struct file *filp, char *buf, size_t count, loff_t *f_pos)
	Char Device read function. Allways called from user space by FS Deamon. The deamon reads content of output_buffer and sends it as commands and data to database. On empty output buffer (zero declared length) the caller will be blocked - added into wait queue. The caller will be woken up after writing any data into output buffer from kernel FS. This function don't support reading larger ammount of data then output buffer size. Greater number of char to be read can be specified, but the maximum ouput buffer length is returned. If count is less than output_buffer length, count characters will be read, but the kernel FS remains blocked until whole output_buffer is read.
ssize_t	fsc_write (struct file *filp, const char *buf, size_t count, loff_t *f_pos)
	Char Device write function.
int	fsc_release (struct inode *inode, struct file *filp)
	Release (close) the char device.
int	fsc_open (struct inode *inode, struct file *filp)
	Open the char device.
void	fsc_init (void)
	FS Character Device initialization.
void	fsc_fini (void)
	FS Character Device fini.
int	fsc_read_procmem (char *buf, char **start, off_t offset, int count, int *eof, void *data)
	Prints information about the fsc device.
int	fsc_waitforempty_output (void)
	Wait for empty output buffer.
int	fsc_waitforfull_input (void)
	Wait for full input buffer.
int	__fsc_query__ (const char *out_buf, const int out_count, char *in_buf, int in_count)
	File System Char Device communication channel.
int	fsc_query (const char *out_buf, const int out_count, char *in_buf, int in_count)
Variables
buffer	fsc_output_buffer
buffer	fsc_input_buffer
atomic_t	fsc_available = ATOMIC_INIT(1)
semaphore	fsc_sem
mutex	query_mutex
int	fsc_major = 0
file_operations	fsc_fops

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Detailed Description

FS Char Device settings, implementation.

Author:

Michal Podzimek, Michal Ficek, Tomas Pop, MFF UK, 2007

This file implements special char device used for comunication between kernel part of a filesystem and userspace deamon. Be carefull if using it this char device has very special behaviour, in some cases it behaves more like block device Especialy We mean this two features

• All the data in buffer are read at once and the real lenght of data is returned
• After reading all the data never 0 is returned like in clasical chardevices

Definition in file fsc_device.c.

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