What is Class_create?

DESCRIPTION This is used to create a struct class pointer that can then be used in calls to device_create. Note, the pointer created here is to be destroyed when finished by making a call to class_destroy.

What is Register_chrdev?

register_chrdev(major, name, fops); stores the given name (a string) and fops (a struct file_operations *) in the entry of the array chrdevs[] indexed by the integer major , the major device number of the device. (Devices have a number, the device number, a combination of major and minor device number.

What does struct Cdev C_dev represent in kernel space?

struct cdev represent a character device within the kernel. All streaming devices(ex: uart, keyboard) falls under the character device category and is available in user-space as a device node file (ex: /dev/ttyS0). User applications accesses the device by using the standard File I/O operations.

What is Mkdev in Linux?

Given two integers, MKDEV combines them into one 32 bit number. This is done by left shifting the major number MINORBIT times i.e. 20 times and then oring the result with the minor number. For e.g. if the major number is 2 => 000010 and the minor number is 1 => 000001.

What is the use of Class_create?

This is used to create a struct class pointer that can then be used in calls to device_create.

What is Err_ptr?

Using ERR_PTR() include/linux/err. h ; to encode a negative error number into a pointer, and IS_ERR() and PTR_ERR() to get it back out again: avoids a separate pointer parameter for the error number. Icky, but in a good way. Prev. Up.

What is Chardev?

The -chardev option is what creates and configures this back end. The “front end” is the part on the QEMU side of this. The most common use is a UART (serial port), but you can also use chardevs to specify how to talk to the QEMU monitor, or to a guest parallel port.

What is Loff_t?

“loff_t” is a “long offset”, i.e., a seek position that unifies the crazy diversity of off_t , off64_t , and so on, so that drivers can just use loff_t and not worry about it.

What is Dev_t Dev?

The Internal Representation of Device Numbers Within the kernel, the dev_t type (defined in ) is used to hold device numbers—both the major and minor parts. As of Version 2.6. 0 of the kernel, dev_t is a 32-bit quantity with 12 bits set aside for the major number and 20 for the minor number.

What does Mknod do in Linux?

mknod is the command used to create device files, which can act strangely compared to normal files. Device files are kept in /dev, and unlike normal files, these are files the kernel knows about, and reads/writes to.

What is Dev_t in Linux?

How use Mknod command in Linux?

Examples

1. To create the special file for a new diskette drive, enter the following command: mknod /dev/fd2 b 1 2.
2. To create the special file for a new character drive, enter the following command: mknod /dev/fc1 b 1 2.
3. To create a FIFO pipe file, enter the following command: mknod fifo1 p.