5.3.3. Registering a character driver

• inform kernel about what operations the driver provide for a device

• struct file_operations in include/linux/fs.h

• error handling (goto's, errno)

• carefull: driver can be called as soon as it has registered! (cdev_add)

• object orientation?

API: Character driver registration

type:

struct cdev

allocate at runtime: (need to add fops by hand)

struct cdev* cdev_alloc(void);
...
my_cdev->ops = &my_fops;

allocate statically and only initalize at runtime:

void cdev_init (struct cdev* cdev, const struct file_operations *fops);

for both cases initalize owner field to THIS_MODULE:

my_cdev.owner = THIS_MODULE;

register the character driver with the kernel:

int cdev_add(struct cdev *dev, dev_t num, unsigned int count);

• cdev: the initalized struct cdev
• num: first device number of device
• count: number of minor numbers

remove (and if necessary free memory):

void cdev_del(struct cdev *dev);

include/linux/cdev.h

old way (do not use anymore):

int register_chrdev(unsigned int major, const char *name, struct file_operations *fops);
void unregister_chrdev(unsigned int major, const char *name);