Skip to content

Instantly share code, notes, and snippets.

@dhilst
Created August 5, 2013 00:01
Show Gist options
  • Save dhilst/6152604 to your computer and use it in GitHub Desktop.
Save dhilst/6152604 to your computer and use it in GitHub Desktop.
cdev06
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/semaphore.h>
#include <linux/slab.h>
#include <linux/sysfs.h>
#include <linux/fs.h>
#include <asm/uaccess.h>
#define MODULE_NAME "cdev06.c"
#define DEBUG(msg, args...) do { \
printk(KERN_DEBUG MODULE_NAME " %s()@%d " msg, __func__, __LINE__, ##args); \
} while (0)
#define DEVICE_NAME "gdev"
#define FIRST 0
static int ndevs = 0;
struct gdev_s {
dev_t dev;
struct cdev *cdev;
struct class *class;
struct device **device;
};
struct gdev_buffer_s {
char *buffer;
int len;
};
static struct gdev_buffer_s gbuffer[] = {
{ "Hello World\n", 12 },
{ "How are you doing\n", 18 },
{ "You should play *skyrim* a little\n", 34 },
{ "I could be leveling right now\n", 30 },
{ "Don't play tibia, is too hard\n", 31 },
{ "Fuz ho dah!\n", 12 },
};
/* static char *hello = "Hello World\n"; */
/* static int hello_len = 12; */
static struct gdev_s gdev;
static int dev_open(struct inode *ip, struct file *fp)
{
return 0;
}
static int dev_release(struct inode *ip, struct file *fp)
{
return 0;
}
static ssize_t dev_read(struct file *fp,
char *buf,
size_t len,
loff_t *off)
{
int tocopy;
int copied;
int i = MINOR(fp->f_inode->i_rdev) - FIRST;
char *hello = gbuffer[i].buffer;
int hello_len = gbuffer[i].len;
DEBUG("dev_read() called with device %d:%d",
MAJOR(fp->f_inode->i_rdev), MINOR(fp->f_inode->i_rdev));
if (*off > len)
return 0;
if (len + *off > hello_len)
len = hello_len - *off;
tocopy = copy_to_user(buf + *off,
hello,
len);
copied = len - tocopy;
*off += copied;
return copied;
}
struct file_operations fops = {
.owner = THIS_MODULE,
.read = dev_read,
.open = dev_open,
.release = dev_release,
};
int init_module(void)
{
int error;
int rval;
int i = 0;
DEBUG("module initialize");
/* determine the number of devices to create */
ndevs = sizeof(gbuffer) / sizeof (gbuffer[0]);
error = alloc_chrdev_region(&gdev.dev, FIRST, ndevs, DEVICE_NAME);
if (error) {
DEBUG("alloc_chrdev_region() fails");
return -1;
}
gdev.class = class_create(THIS_MODULE, "gko");
if (IS_ERR(gdev.class)) {
DEBUG("class_create() fails");
goto class_error;
}
gdev.cdev = cdev_alloc();
if (!gdev.cdev) {
DEBUG("alloc_cdev() fails at %i", i);
goto cdev_error;
}
cdev_init(gdev.cdev, &fops);
rval = cdev_add(gdev.cdev, gdev.dev, ndevs);
if (rval < 0) {
DEBUG("cdev_add() fails");
goto cdev_error;
}
gdev.device = kmalloc(sizeof (struct device *) * ndevs, GFP_KERNEL);
if (!gdev.device) {
DEBUG("kamalloc() fails");
goto cdev_error;
}
DEBUG("ndevs = %d", ndevs);
for (i = 0; i < ndevs; i++) {
int minor = MINOR(gdev.dev) + i;
int major = MAJOR(gdev.dev);
gdev.device[i] = device_create(gdev.class, NULL,
MKDEV(major, minor),
NULL, "gdev%d", minor);
if (IS_ERR(gdev.device[i])) {
DEBUG("device_create() fails");
goto device_error;
} else
DEBUG("device gdev%d created", minor);
}
return 0;
device_error:
do {
int j;
for (j = 0; j < i; j++)
device_destroy(gdev.class, MKDEV(MAJOR(gdev.dev),
MINOR(gdev.dev) + j));
} while (0);
kfree(gdev.device);
cdev_error:
cdev_del(gdev.cdev);
unregister_chrdev_region(gdev.dev, ndevs);
class_error:
class_unregister(gdev.class);
class_destroy(gdev.class);
return -1;
}
void cleanup_module(void)
{
int i;
for (i = 0; i < ndevs; i++)
device_destroy(gdev.class, MKDEV(MAJOR(gdev.dev),
MINOR(gdev.dev) + i));
class_unregister(gdev.class);
class_destroy(gdev.class);
cdev_del(gdev.cdev);
unregister_chrdev_region(gdev.dev, ndevs);
}
MODULE_LICENSE("GPL");
obj-m += cdev06.o
KDIR = /home/geckos/abs/linux/src/linux-3.10
all:
make -C $(KDIR) M=$(PWD) modules
clean:
make -C $(KDIR) M=$(PWD) clean
@rm -v *~
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment