passing floating point by casting to int and print in ioctl implementation - c

so I have this code
this is what I am doing in ioctl implementation
if( copy_from_user(&value ,(struct aa*) arg, sizeof(value)) )
{
pr_err("Data Write : Err!\n");
}
__u64 a=value.a;
__u32 *b=(__u32 *)a;
pr_info("wow Value = [%x]\n", (int)b[0]);
but I am passing from userspace float so but my passed values are not correctly printing in printk
this is my program
struct aa
{
uint64_t a;
};
#define WR_VALUE _IOW('a','a',struct aa*)
#define RD_VALUE _IOR('a','b',struct aa*)
int main()
{
struct aa a;
float *f=(float[]){2,2,3};
a.a=(uint64_t)f;
printf("sizeof = %zu\n",sizeof(*f));
int fd;
int32_t value, number;
printf("*********************************\n");
printf("*******WWW.EmbeTronicX.com*******\n");
printf("\nOpening Driver\n");
fd = open("/dev/etx_device", O_RDWR);
if(fd < 0) {
printf("Cannot open device file...\n");
return 0;
}
printf("Enter the Value to send\n");
scanf("%d",&number);
printf("Writing Value to Driver\n");
ioctl(fd, WR_VALUE, (struct aa *) &a);
printf("Reading Value from Driver\n");
ioctl(fd, RD_VALUE, (struct aa*) &a);
printf("Value is %d\n", value);
printf("Closing Driver\n");
close(fd);
}
full code
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kdev_t.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include<linux/slab.h> //kmalloc()
#include<linux/uaccess.h> //copy_to/from_user()
#include <linux/ioctl.h>
#include <asm/fpu/api.h>
struct aa
{
__u64 a;
};
#define WR_VALUE _IOW('a','a',struct aa *)
#define RD_VALUE _IOR('a','b',struct aa *)
struct aa value;
dev_t dev = 0;
static struct class *dev_class;
static struct cdev etx_cdev;
/*
** Function Prototypes
*/
static int __init etx_driver_init(void);
static void __exit etx_driver_exit(void);
static int etx_open(struct inode *inode, struct file *file);
static int etx_release(struct inode *inode, struct file *file);
static ssize_t etx_read(struct file *filp, char __user *buf, size_t len,loff_t * off);
static ssize_t etx_write(struct file *filp, const char *buf, size_t len, loff_t * off);
static long etx_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
/*
** File operation sturcture
*/
static struct file_operations fops =
{
.owner = THIS_MODULE,
.open = etx_open,
.unlocked_ioctl = etx_ioctl,
.release = etx_release,
};
/*
** This function will be called when we open the Device file
*/
static int etx_open(struct inode *inode, struct file *file)
{
return 0;
}
/*
** This function will be called when we close the Device file
*/
static int etx_release(struct inode *inode, struct file *file)
{
return 0;
}
static long etx_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
switch(cmd) {
case WR_VALUE:
if( copy_from_user(&value ,(struct aa*) arg, sizeof(value)) )
{
pr_err("Data Write : Err!\n");
}
__u64 a=value.a;
__u32 *b=(__u32 *)a;
pr_info("wow Value = [%x]\n", (int)b[0]);
kernel_fpu_end();
break;
case RD_VALUE:
if( copy_to_user((struct aa*) arg, &value, sizeof(value)) )
{
pr_err("Data Read : Err!\n");
}
break;
default:
pr_info("Default\n");
break;
}
return 0;
}
/*
** Module Init function
*/
static int __init etx_driver_init(void)
{
/*Allocating Major number*/
if((alloc_chrdev_region(&dev, 0, 1, "etx_Dev")) <0){
pr_err("Cannot allocate major number\n");
return -1;
}
pr_info("Major = %d Minor = %d \n",MAJOR(dev), MINOR(dev));
/*Creating cdev structure*/
cdev_init(&etx_cdev,&fops);
/*Adding character device to the system*/
if((cdev_add(&etx_cdev,dev,1)) < 0){
pr_err("Cannot add the device to the system\n");
goto r_class;
}
/*Creating struct class*/
if((dev_class = class_create(THIS_MODULE,"etx_class")) == NULL){
pr_err("Cannot create the struct class\n");
goto r_class;
}
/*Creating device*/
if((device_create(dev_class,NULL,dev,NULL,"etx_device")) == NULL){
pr_err("Cannot create the Device 1\n");
goto r_device;
}
pr_info("Device Driver Insert...Done!!!\n");
return 0;
r_device:
class_destroy(dev_class);
r_class:
unregister_chrdev_region(dev,1);
return -1;
}
/*
** Module exit function
*/
static void __exit etx_driver_exit(void)
{
device_destroy(dev_class,dev);
class_destroy(dev_class);
cdev_del(&etx_cdev);
unregister_chrdev_region(dev, 1);
pr_info("Device Driver Remove...Done!!!\n");
}
module_init(etx_driver_init);
module_exit(etx_driver_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("EmbeTronicX <embetronicx#gmail.com>");
MODULE_DESCRIPTION("Simple Linux device driver (IOCTL)");
MODULE_VERSION("1.5");
what am I doing wrong in kernel ioctl because I casted float to uint_64 like a.a=(uint64_t)f; and passed struct a to kernel now I want to read float *f elements passed from userspace through ioctl in ioctl implementation

Related

How to get struct i2c_client *client structure inside kernel thread

I am now developing a kernel module to handle two digits 7-segment led indicator via I2C device on RaspberryPi4 with RaspberryPiOS.
This module uses kernel thread to handle 7-segment led display, change digit position.
Sending command to i2c device requires i2c_client* structure, it can be obtained via formal argument of probe function.
Kernel thread does not have formal argument of i2c_client structure.
My solution is to store a pointer of i2c_client* structure into a global variable and use this pointer inside kernel thread, and call i2c function with this pointer.
My kernel module works well, at least now...
Do you have better solution to use i2c function in kernel thread? or exists better solution?
My entire code is below...
//i2c_7seg2_udev.c
#include <linux/init.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/i2c.h>
#include <asm/uaccess.h>
#include <linux/workqueue.h>
#include <linux/delay.h>
#include <linux/kthread.h>
MODULE_LICENSE("GPL v2");
#define DEVICE_NAME "i2c_7seg2_udev"
#define MINOR_BASE 0
#define MINOR_NUM 1
static unsigned int major_num;
struct cdev i2c_7seg2_udev_cdev;
void init_i2c_gpio(void);
void turn_off_7seg(void);
void turn_off_7seg(void);
void set_7seg(unsigned int number);
void change_7seg_keta(void);
#define LOOP_SLEEP_US (5000)
static struct task_struct *kthread;
static int dynamic_7seg_kthread(void *data);
static void init_kthread(void)
;
static int dynamic_7seg_kthread(void *data)
{
while(!kthread_should_stop()){
change_7seg_keta();
usleep_range(LOOP_SLEEP_US, LOOP_SLEEP_US * 2);
}
return 0;
}
static void init_kthread(void)
{
kthread = kthread_create(dynamic_7seg_kthread, NULL, "dynamic_7seg_kthread");
wake_up_process(kthread);
}
static int init_regist_device(void);
static struct i2c_client *i2c_client_data;
#define DRIVER_NAME "i2c_7seg2_udev"
static struct i2c_device_id i2c_7seg2_udev_device_idtable[] = {
{"I2C_7SEG2_UDEV", 0},
{ }
};
MODULE_DEVICE_TABLE(i2c, i2c_7seg2_udev_device_idtable);
static int i2c_7seg2_udev_device_probe(struct i2c_client *client, const struct i2c_device_id *id)
{
if(init_regist_device() < 0){
printk(KERN_DEBUG "i2c_7seg2_udev: initialize failed.\n");
return -1;
}
printk(KERN_DEBUG "i2c_7seg2_udev_device connected.\n");
printk(KERN_DEBUG "id.name = %s, id.driver_data = %ld", id->name, id->driver_data);
printk(KERN_DEBUG "device address is: 0x%02X\n", client->addr);
i2c_client_data = client;
init_i2c_gpio();
set_7seg(12);
init_kthread();
return 0;
}
static int i2c_7seg2_udev_device_remove(struct i2c_client *client)
{
dev_t dev;
turn_off_7seg();
printk(KERN_DEBUG "i2c_7seg2_udev: wait for thread to be terminated.\n");
kthread_stop(kthread);
printk(KERN_DEBUG "i2c_7seg2_udev: thread terminated.\n");
dev = MKDEV(major_num, MINOR_BASE);
cdev_del(&i2c_7seg2_udev_cdev);
unregister_chrdev_region(dev, MINOR_NUM);
printk(KERN_DEBUG "i2c_7seg2_udev_device disconnected.\n");
return 0;
}
static struct i2c_driver i2c_7seg2_udev_device_driver = {
.driver = {
.name = DRIVER_NAME,
.owner = THIS_MODULE,
},
.id_table = i2c_7seg2_udev_device_idtable,
.probe = i2c_7seg2_udev_device_probe,
.remove = i2c_7seg2_udev_device_remove,
};
#define MAX_7SEG_KETA (2)
//NOTE: "KETA" means digit position, in Japanese.
static const unsigned int seg7_pattern[] =
//--gfedcba
{0b00111111, //0
0b00000110, //1
0b01011011, //2
0b01001111, //3
0b01100110, //4
0b01101101, //5
0b01111100, //6
0b00100111, //7
0b01111111, //8
0b01100111 //9
};
unsigned char value_7seg[MAX_7SEG_KETA];
DEFINE_MUTEX(__mutex_value_7seg);
void set_7seg(unsigned int number){
unsigned int i;
printk(KERN_DEBUG "i2c_7seg2_udev: value %d .\n", number);
for( i = 0; i < MAX_7SEG_KETA; i++){
value_7seg[MAX_7SEG_KETA - i - 1] = (number % 10) + '0';
number = number / 10;
}
}
void change_7seg_keta(void)
{
static unsigned int keta = 0;
unsigned char keta_shift;
unsigned int number;
keta_shift = 0x01 << keta;
i2c_smbus_write_byte_data(i2c_client_data, 0x03, ~keta_shift); //P1に出力
number = value_7seg[MAX_7SEG_KETA - keta - 1] - '0';
i2c_smbus_write_byte_data(i2c_client_data, 0x02, ~seg7_pattern[number]); //P0に出力
keta ++;
if( keta >= MAX_7SEG_KETA ){
keta = 0;
}
}
void turn_off_7seg(void){
i2c_smbus_write_byte_data(i2c_client_data, 0x02, 0x7F); //P0に出力
}
void init_i2c_gpio(void){
i2c_smbus_write_byte_data(i2c_client_data, 0x06, 0x00);
i2c_smbus_write_byte_data(i2c_client_data, 0x07, 0x00);
}
static int i2c_7seg2_udev_open(struct inode *inode, struct file *file)
{
printk(KERN_DEBUG "i2c_7seg2_udev: opened.\n");
return 0;
}
static int i2c_7seg2_udev_close(struct inode *inode, struct file *file)
{
printk(KERN_DEBUG "i2c_7seg2_udev: closed.\n");
return 0;
}
static ssize_t i2c_7seg2_udev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
{
unsigned char read_datas[MAX_7SEG_KETA + 2];
unsigned long bytes_left;
const unsigned long bytes_to_send = MAX_7SEG_KETA + 2;
unsigned int i;
for(i = 0; i < MAX_7SEG_KETA; i++ ){
read_datas[i] = value_7seg[i];
}
read_datas[i] = '\n';
read_datas[i + 1] = '\0';
bytes_left = copy_to_user(buf, read_datas, bytes_to_send);
return (bytes_to_send - bytes_left);
}
static ssize_t i2c_7seg2_udev_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_pos)
{
unsigned char write_values[MAX_7SEG_KETA + 2];
unsigned long bytes_left;
const unsigned long bytes_to_send = MAX_7SEG_KETA + 2;
int i;
printk(KERN_DEBUG "i2c_7seg2_udev: write.");
printk(KERN_DEBUG "i2c_7seg2_udev: write.");
bytes_left = copy_from_user(write_values, buf, bytes_to_send);
mutex_lock(&__mutex_value_7seg);
for(i = 0; i < MAX_7SEG_KETA; i++){
if( (write_values[i] >= '0') && (write_values[i] <= '9') ){
value_7seg[i] = write_values[i];
}
}
mutex_unlock(&__mutex_value_7seg);
return (bytes_to_send - bytes_left);
}
struct file_operations s_i2c_7seg2_udev_fops = {
.open = i2c_7seg2_udev_open,
.release = i2c_7seg2_udev_close,
.read = i2c_7seg2_udev_read,
.write = i2c_7seg2_udev_write,
};
int init_regist_device(void)
{
int device_num = 0;
int devnum_err = 0;
int cdev_err = 0;
dev_t dev;
devnum_err = alloc_chrdev_region(&dev, MINOR_BASE, MINOR_NUM, DEVICE_NAME);
if (devnum_err != 0) {
printk(KERN_ERR "devnum_err = %d\n", devnum_err);
return -1;
}
if (device_num != 0) {
printk(KERN_ERR "i2c_7seg2_udev: error_init_regist_device , %d\n", device_num);
return -1;
}
major_num = MAJOR(dev);
cdev_init(&i2c_7seg2_udev_cdev, &s_i2c_7seg2_udev_fops);
i2c_7seg2_udev_cdev.owner = THIS_MODULE;
cdev_err = cdev_add(&i2c_7seg2_udev_cdev, dev, MINOR_NUM);
if (cdev_err != 0) {
printk(KERN_ERR "cdev_add = %d\n", cdev_err);
unregister_chrdev_region(dev, MINOR_NUM);
return -1;
}
printk(KERN_DEBUG "i2c_7seg2_udev: device registerd.\n");
return 0;
}
static int i2c_7seg2_udev_device_init(void)
{
printk(KERN_DEBUG "i2c_7seg2_udev device driver loaded.\n");
i2c_add_driver(&i2c_7seg2_udev_device_driver);
return 0;
}
static void i2c_7seg2_udev_device_exit(void)
{
printk(KERN_DEBUG "i2c_7seg2_udev device driver unloading.\n");
i2c_del_driver(&i2c_7seg2_udev_device_driver);
}
module_init(i2c_7seg2_udev_device_init);
module_exit(i2c_7seg2_udev_device_exit);
The second argument of the function kthread_create() is void *data.
Right now you are passing NULL, you can pass your pointer to the struct i2c_client instead.
Then you can do:
static int dynamic_7seg_kthread(void *data) {
struct i2c_client *client = data;
while (!kthread_should_stop()) {
change_7seg_keta(client);
usleep_range(LOOP_SLEEP_US, LOOP_SLEEP_US * 2);
}
return 0;
}
Thus eliminating global variable from the code.

One ioctl not being executed in kernel module

I wrote a kernel module demonstrating on how ioctl works.
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/kdev_t.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/cdev.h>
#include <linux/uaccess.h>
int base_minor = 0;
char *device_name = "msg";
int count = 1;
dev_t devicenumber;
static struct class *class = NULL;
static struct device *device = NULL;
static struct cdev mycdev;
#define MAX_SIZE 1024
char kernel_buffer[MAX_SIZE];
int buffer_index;
MODULE_LICENSE("GPL");
static int device_open(struct inode *inode, struct file *file)
{
pr_info("%s\n", __func__);
file->f_pos = 0;
buffer_index = 0;
return 0;
}
static int device_release(struct inode *inode, struct file *file)
{
pr_info("%s\n", __func__);
return 0;
}
static ssize_t device_read(struct file *file, char __user *user_buffer,
size_t read_count, loff_t *offset)
{
int bytes_read;
int available_space;
int bytes_to_read;
pr_info("%s read offset:%lld\n", __func__, *offset);
available_space = MAX_SIZE - *(offset);
if (read_count < available_space)
bytes_to_read = read_count;
else
bytes_to_read = available_space;
pr_info("bytes_to_read:%d\n", bytes_to_read);
if (bytes_to_read == 0) {
pr_err("%s: No available space in the buffer for reading\n",
__func__);
return -ENOSPC;
}
if (buffer_index > *offset)
bytes_to_read = buffer_index - *offset;
else
return 0;
bytes_read = bytes_to_read - copy_to_user(user_buffer, kernel_buffer+*offset, bytes_to_read);
pr_info("%s: Copy to user returned:%d\n", __func__, bytes_to_read);
//update file offset
*offset += bytes_read;
return bytes_read;
}
static ssize_t device_write(struct file *file, const char __user *user_buffer,
size_t write_count, loff_t *offset)
{
int bytes_written;
int available_space;
int bytes_to_write;
pr_info("%s write offset:%lld\n", __func__, *offset);
available_space = MAX_SIZE - *(offset);
if (write_count < available_space)
bytes_to_write = write_count;
else
bytes_to_write = available_space;
if (bytes_to_write == 0) {
pr_err("%s: No available space in the buffer for writing\n",
__func__);
return -ENOSPC;
}
bytes_written = bytes_to_write - copy_from_user(kernel_buffer+*offset, user_buffer, bytes_to_write);
pr_info("%s: Bytes written:%d\n", __func__, bytes_written);
pr_info("%s: kernel_buffer:%s\n", __func__, kernel_buffer);
//update file offset
*offset += bytes_written;
buffer_index += bytes_written;
return bytes_written;
}
static loff_t device_lseek(struct file *file, loff_t offset, int orig)
{
loff_t new_pos = 0;
switch(orig) {
case 0 : /*seek set*/
new_pos = offset;
break;
case 1 : /*seek cur*/
new_pos = file->f_pos + offset;
break;
case 2 : /*seek end*/
new_pos = MAX_SIZE - offset;
break;
}
if(new_pos > MAX_SIZE)
new_pos = MAX_SIZE;
if(new_pos < 0)
new_pos = 0;
file->f_pos = new_pos;
return new_pos;
}
long device_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
unsigned char ch;
pr_info("%s: Cmd:%u\t Arg:%lu\n", __func__, cmd, arg);
switch(cmd)
{
//Get Length of buffer
case 0x01:
pr_info("Get Buffer Length\n");
put_user(MAX_SIZE, (unsigned int *)arg);
break;
//clear buffer
case 0x02:
pr_info("Clear buffer\n");
memset(kernel_buffer, 0, sizeof(kernel_buffer));
break;
//fill character
case 0x03:
get_user(ch, (unsigned char *)arg);
pr_info("Fill Character:%c\n", ch);
memset(kernel_buffer, ch, sizeof(kernel_buffer));
buffer_index = sizeof(kernel_buffer);
break;
default:
pr_info("Unknown Command:%u\n", cmd);
return -EINVAL;
}
return 0;
}
struct file_operations device_fops = {
.read = device_read,
.write = device_write,
.open = device_open,
.release = device_release,
.llseek = device_lseek,
.unlocked_ioctl = device_ioctl
};
static int test_hello_init(void)
{
class = class_create(THIS_MODULE, "myclass");
if (!alloc_chrdev_region(&devicenumber, base_minor, count, device_name)) {
printk("Device number registered\n");
printk("Major number received:%d\n", MAJOR(devicenumber));
device = device_create(class, NULL, devicenumber, NULL, device_name);
cdev_init(&mycdev, &device_fops);
mycdev.owner = THIS_MODULE;
cdev_add(&mycdev, devicenumber, count);
}
else
printk("Device number registration Failed\n");
return 0;
}
static void test_hello_exit(void)
{
device_destroy(class, devicenumber);
class_destroy(class);
cdev_del(&mycdev);
unregister_chrdev_region(devicenumber, count);
}
module_init(test_hello_init);
module_exit(test_hello_exit);
Then i wrote a user space code
#include <stdio.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/ioctl.h>
int main(int argc, char *argv[])
{
char buffer[1024];
int fd;
unsigned int length;
unsigned char ch = 'A';
int i = 0;
fd = open("/dev/msg", O_RDWR);
if (fd < 0) {
perror("fd failed");
exit(2);
}
//Get Length - 0x01
ioctl(fd, 0x01, &length);
printf("Length:%u\n", length);
ioctl(fd, 0x02);
//Set Character - 0x03
ioctl(fd, 0x03, &ch);
perror("ioctl");
lseek(fd, 0, SEEK_SET);
perror("lseek");
length = read(fd, buffer, 1024);
perror("Read");
printf("length:%d\n", length);
buffer[1023] = '\0';
printf("Buffer:%s\n", buffer);
close(fd);
}
ioctl commands 1, 3 work but not 2. Can you please provide what's the mistake in the code
You should review the requirements for ioctl on the man page:
DESCRIPTION
The ioctl() system call manipulates the underlying device parameters of
special files. In particular, many operating characteristics of char‐
acter special files (e.g., terminals) may be controlled with ioctl()
requests. The argument fd must be an open file descriptor.
The second argument is a device-dependent request code. The third
argument is an untyped pointer to memory. It's traditionally char
*argp (from the days before void * was valid C), and will be so named
for this discussion.
An ioctl() request has encoded in it whether the argument is an in
parameter or out parameter, and the size of the argument argp in bytes.
Macros and defines used in specifying an ioctl() request are located in
the file <sys/ioctl.h>.

writing driver - "Failed to register device class"

I am trying to write a character device driver based on this tutorial.
But when trying to insert my module I get the following error:
$ sudo insmod modules/main/main.ko
insmod: ERROR: could not insert module modules/main/main.ko: Operation not permitted
$dmesg
[ 1085.409026] Failed to register device class
This is the corresponding code snippet:
#ifndef __KERNEL__
#define __KERNEL__
#endif
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/device.h>
#define CLASS_NAME "my_class"
#define DEV_NAME "my_device"
static int dev_open(struct inode *, struct file *);
static int dev_release(struct inode *, struct file *);
static ssize_t dev_read(struct file *, char *, size_t, loff_t *);
static ssize_t dev_write(struct file *, const char *, size_t, loff_t *);
static int myCharClass;
static int myCharDevice;
int majorNumber;
static struct file_operations fops =
{
.open = dev_open,
.read = dev_read,
.write = dev_write,
.release = dev_release
};
int init_module(void)
{
printk("Hello world - DAO \n");
majorNumber = register_chrdev(0, DEV_NAME, &fops);
if (majorNumber < 0)
{
printk("Error when registering character device driver.\n");
return -1;
}
myCharClass = class_create(THIS_MODULE, CLASS_NAME);
if (IS_ERR(myCharClass))
{
unregister_chrdev(majorNumber, DEV_NAME);
printk(KERN_ALERT "Failed to register device class\n");
return -1;
}
myCharDevice = device_create(myCharClass, NULL, MKDEV(majorNumber, 0), NULL, DEV_NAME);
if (IS_ERR(myCharDevice))
{
class_destroy(myCharClass);
unregister_chrdev(majorNumber, DEV_NAME);
printk(KERN_ALERT "Failed to create the device\n");
return -1;
}
return 0;
}
void cleanup_module(void)
{
printk("<1> Ciao - DAO\n");
}
static int dev_open(struct inode *p_inode, struct file *p_file)
{
printk("Opened device.\n");
return 0;
}
static ssize_t dev_read(struct file *filep, char *buffer, size_t len, loff_t *offset)
{
printk("Reading device.\n");
return 0;
}
static ssize_t dev_write(struct file *filep, const char *buffer, size_t len, loff_t *offset)
{
printk("Writing device\n");
return 0;
}
static int dev_release(struct inode *inodep, struct file *filep)
{
printk("Releasing device.\n");
return 0;
}
MODULE_LICENSE("GPL");
Does anybody know what I am doing incorrectly?
I had a look at this post, but it didn't really help me, because I didn't really what the issue is.
Thanks

IOCTL call not working with driver

I wrote a IOCTL driver and a corresponding ioctl app with a header file containing commands.
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kdev_t.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <asm/uaccess.h>
#include "myioctl.h"
#include <linux/ioctl.h>
#define NAME MyCharDevice
//Function Prototypes
int NAME_open(struct inode *inode, struct file *filp);
int NAME_release(struct inode *indoe, struct file *filp);
ssize_t NAME_write(struct file *filp, char __user *Ubuff, size_t count, loff_t *offp);
ssize_t NAME_read(struct file *filp, char __user *Ubuff, size_t count, loff_t *offp);
int NAME_flush (struct file *filp);
int NAME_IOCTL (struct inode *inode, struct file *filp, unsigned long cmd, unsigned long val);
//Structure that defines the operations that the driver provides
struct file_operations fops =
{
.owner = THIS_MODULE,
.open = NAME_open,
.read = NAME_read,
.write = NAME_write,
.unlocked_ioctl = NAME_IOCTL,
.release = NAME_release,
.flush = NAME_flush,
};
//Structure for a character driver
struct cdev *my_cdev;
//Init Module
static int __init CharDevice_init(void)
{
int result;
int MAJOR,MINOR;
dev_t Mydev;
Mydev = MKDEV(255,0);//Create a device number
MAJOR=MAJOR(Mydev);
MINOR=MINOR(Mydev);
printk("\nThe Major Number is %d...THe Minor Number is %d\n",MAJOR,MINOR);
result=register_chrdev_region(Mydev,1,"MyCharDevice");//register device region.....
if(result<0)
{
printk(KERN_ALERT "\nThe Region requested for is not obtainable\n");
return(-1);
}
my_cdev = cdev_alloc();//allocate memory to Char Device structure
my_cdev->ops = &fops;//link our file operations to the char device
result=cdev_add(my_cdev,Mydev,1);//Notify the kernel abt the new device
if(result<0)
{
printk(KERN_ALERT "\nThe Char Devide has not been created......\n");
return (-1);
}
return 0;
}
//Cleanup Module
void __exit CharDevice_exit(void)
{
dev_t Mydev;
int MAJOR,MINOR;
Mydev=MKDEV(255,0);
MAJOR=MAJOR(Mydev);
MINOR=MINOR(Mydev);
printk("\nThe Major Number is %d...THe Minor Number is %d\n",MAJOR,MINOR);
unregister_chrdev_region(Mydev,1);//unregister the device numbers and the device created
cdev_del(my_cdev);
printk(KERN_ALERT "\nI have unregistered the stuff that was allocated.....Goodbye for ever.....\n");
return;
}
int NAME_IOCTL (struct inode *inode, struct file *filp, unsigned long cmd, unsigned long val)
{
int BAUD=0, STOP;
char PARITY, CONFIG;
printk ("In IOCTL\n");
printk("command = %d %d val = %d\n", cmd, SET_BAUD, val);
switch (cmd) {
case SET_BAUD:
get_user (BAUD, (int *)val);
printk ("The baud is %d", BAUD);
case SET_PARITY:
case SET_STOP:
case READ_CONFIG:
default:
return -1;
}
return 0;
}
//Open System Call
int NAME_open(struct inode *inode, struct file *filp)
{
printk(KERN_ALERT "\nThis is the Kernel....Open Call.....I have nothing to do.....but YOU ALL HAVE....HAHAHAHA...\n");
return 0;
}
//Close System Call
int NAME_release(struct inode *indoe, struct file *filp)
{
printk(KERN_ALERT "\nThis is the release method of my Character Driver......Bye Dudes......\n");
return 0;
}
//Write Functionality
ssize_t NAME_write(struct file *filp, char __user *Ubuff, size_t count, loff_t *offp)
{
char Kbuff[80];
unsigned long result;
ssize_t retval;
//strcpy(Kbuff,Ubuff);
result=copy_from_user((char *)Kbuff,(char *)Ubuff,count); //get user data
if(result==0)
{
printk(KERN_ALERT "\nMessage from the user......\n>>>> %s <<<<\n",Kbuff);
printk(KERN_ALERT "\n Data Successfully Written.....\n");
retval=count;
return retval;
}
else
{
printk(KERN_ALERT "\n Error Writing Data\n");
retval=-EFAULT;
return retval;
}
}
//read Functionality
ssize_t NAME_read(struct file *filp, char __user *Ubuff, size_t count, loff_t *offp)
{
char Kbuff[]="THis is some date from the kernel to the user....User,ENJOY......";
unsigned long result;
ssize_t retval;
//strcpy(Kbuff,Ubuff);
result=copy_to_user((char *)Ubuff,(char *)Kbuff,sizeof(Kbuff)); //copy to user
if(result==0)
{
//printk("\nMessage from the user......\n>>>> %s <<<<\n");
printk(KERN_ALERT "\n Data Successfully read.....\n");
retval=count;
return retval;
}
else
{
printk(KERN_ALERT"\n Error Writing Data to User\n");
retval=-EFAULT;
return retval;
}
}
int NAME_flush (struct file *filp)
{
printk("\n This is the close function of the file....");
return 0;
}
//Module over ride functions
module_init(CharDevice_init);
module_exit(CharDevice_exit);
header file
#define MAGIC 'x'
#define SET_BAUD _IOW(MAGIC,0, int)
#define SET_PARITY _IOW(MAGIC, 1, char)
#define SET_STOP _IOW(MAGIC, 2, int)
#define READ_CONFIG _IOR(MAGIC, 3, int)
c file
#include <stdio.h>
#include <sys/types.h>
#include <fcntl.h>
#include <linux/ioctl.h>
#include "myioctl.h"
int main()
{
int FileDesc, Baud=9600;
// char Ubuff[]="THis is the User Buffer......Sending Data to the Kernel....";
// char Kbuff[100];
FileDesc=open("/dev/MyCharDevice",O_RDWR);
if(FileDesc <0)
{
printf("\nError Opening Device\n");
exit(1);
}
ioctl (FileDesc, SET_BAUD, &Baud);
printf("%d %d \n", SET_BAUD, &Baud);
// write(FileDesc,Ubuff,sizeof(Ubuff));
// read(FileDesc,Kbuff,sizeof(Ubuff));
// printf("\n The Data read from the Kernel is\n>>>> %s <<<<\n",Kbuff);
close(FileDesc);
}
I am printing in driver what are the command and value of the argument that print like this
command = 1622004312 1074034688 val = 1622004312
So sent command is equal to the argument I sent. Why this is happening?
I used older IOCTL prototype in my driver.
it should be of this type
#if (LINUX_VERSION_CODE < KERNEL_VERSION(2,6,35))
static int my_ioctl(struct inode *i, struct file *f, unsigned int cmd, unsigned long arg)
#else
static long my_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
#endif
In my case against my kernel
static long my_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
is the correct type.

char driver node is not opening

I wrote a simple char driver for my beaglebone kernel
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/fs.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("mrigendra.chaubey#gmail.com");
#define DEVICE_NAME "experm"
#define CLASS_NAME "exp"
static struct class* myclass = NULL; ///< The device-driver class struct pointer
static struct device* mychardevice = NULL; ///< The device-driver device struct pointer
static int myopen(struct inode *, struct file *);
static int release(struct inode *, struct file *);
static int myioctl(struct inode *, struct file *, unsigned int cmd, unsigned long arg);
static size_t myread(struct file *,char * , size_t, loff_t *);
static size_t mywrite(struct file *,char * , size_t, loff_t *);
static dev_t mydev;
static int myopen(struct inode *nd, struct file *fp)
{
printk(KERN_INFO "myopen\n");
return 0;
}
static int myrelease(struct inode *nd, struct file *fp)
{
printk(KERN_INFO "myrelease\n");
return 0;
}
static int myioctl(struct inode *nd, struct file *fp, unsigned int cmd, unsigned long arg)
{
printk(KERN_INFO "myioctl\n");
return 0;
}
static size_t myread(struct file *fp, char *buf, size_t len, loff_t *ofs)
{
printk(KERN_INFO "myread\n");
return 0;
}
static size_t mywrite(struct file *fp, char *buf, size_t len, loff_t *ofs)
{
printk(KERN_INFO "mywrite\n");
return 0;
}
static struct file_operations fops = {
.open = myopen,
.release = myrelease,
.read = myread,
.write = mywrite,
.unlocked_ioctl = myioctl,
};
static int __init myinit(void)
{
int err;
//extern int alloc_chrdev_region(dev_t *, unsigned minor number, unsigned total, const char *);
err = alloc_chrdev_region(&mydev, 0, 1, "expermdev");
if(err<0)
{
printk(KERN_INFO "major and minor can't be created, err = %d\n", err);
return err;
}
//struct class * class_create ( struct module *owner, const char *name);
myclass = class_create(THIS_MODULE, CLASS_NAME);
if(IS_ERR(myclass))
{
unregister_chrdev(MAJOR(mydev), "expermdev");
printk(KERN_ALERT "Failed to register device class\n");
return PTR_ERR(myclass);
}
//struct device *device_create(struct class *cls, struct device *parent, dev_t devt, void *drvdata, const char *fmt, ...);
//This function can be used by char device classes. A struct device will be created in sysfs, registered to the specified class.
mychardevice = device_create(myclass, NULL, mydev, NULL, "expermdev");
if(IS_ERR(mychardevice))
{
class_destroy(myclass);
unregister_chrdev(MAJOR(mydev), "expermdev");
printk(KERN_ALERT "Failed to create the device\n");
return PTR_ERR(mychardevice);
}
printk(KERN_INFO "my device created correctly\n");
return 0;
}
static void __exit myexit(void)
{
device_destroy(mychardevice, mydev);
class_unregister(myclass);
class_destroy(myclass);
unregister_chrdev(MAJOR(mydev), "expermdev");
printk(KERN_INFO "exited\n");
}
module_init(myinit);
module_exit(myexit);
and app.c file
#include <stdio.h>
#include<fcntl.h>
int main()
{
int fp;
fp = open ("/dev/expermdev", O_RDWR);
if(fp < 0)
printf("file can't be opened\n");
else
printf("file opened\n");
return 0;
}
I am compiling the driver as a module and insmod it, also compiled app.c with the same cross compiler, and put this binary in bin directory. I ran this bin file, but it says
file can't be opened
What am I doing wrong?
Got it. I did not used cdev struture and added fops to it. After that I have to tell kernel about it.
cdev = cdev_alloc();//allocate memory to Char Device structure
cdev->ops = &fops;//link our file operations to the char device
result=cdev_add(cdev,mydev,1);//Notify the kernel abt the new device
also delete this cdev in exit function before unregistering the driver.
In register_chrdev_region we do both things at the same time, but in dynamic allocation of major and minor numbers we have to use cdev to do the rest.

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