Character Device Drivers in deep

Linux Kernel Programming - Character Device Drivers

(3 ratings)

71 students

Created by Linux Trainer

Last updated 10/2020

English

English [Auto]

30-Day Money-Back Guarantee

What you'll learn

Write character device driver from scratch
Understand the various file operations provided by character driver

Requirements

Should be able to write/compile/load/unload Hello World Linux Kernel Modules

Description

Updated on Oct 10: Added Downloads section

What will you learn from this course?

Introduction to character drivers
What is device number and device file
Allocating device number - statically and dynamically
Creating device file - Manually(mknod) and automatically (udev)
Registering character device and its file operation with Kernel
Copying data from user space to kernel space and vice versa
Understanding the various structures - struct file and struct inode
Implementation of open, release, read, write, llseek, ioctl file operations
How to create multiple device nodes and add support for private data
Flow of write system call from kernel system call entry point to driver write file operations
Handling all the error cases in ioctl implementation
Sending a signal to user space from kernel space
Various access control mechanisms and capabilities
Misc Driver

API's covered in this course:

MAJOR
MINOR
MKDEV
register_chrdev_region
alloc_chrdev_region
class_create
device_create
class_destroy
device_destroy
unregister_chrdev_region
imajor
iminor
copy_from_user
copy_to_user
put_user
get_user
print_dev_t
format_dev_t
strnlen_user
container_of
access_ok

Commands used in this course:

mknod
udevadm monitor

Who this course is for:

Developers interested in learning Linux Kernel Programming

6 sections • 88 lectures • 4h 20m total length

Preview03:36
Preview02:28
Preview00:41
Preview03:32
How to choose a device number
01:58
Data type for device number dev_t
00:50
Example of MAJOR,MINOR,MKDEV macros
03:27
/proc/devices file
01:03
Static Allocation of Device Numbers
01:36
Example of static allocation of device numbers
02:26
Test cases on Previous Example
01:58
Preview01:39
What happens if i try to register same name
01:36
Registering Maximum Minor Numbers
03:27
Preview03:02
Dynamic Allocation of Device Number
00:48
Example of dynamic allocation of device number
01:54
Calling alloc_chrdev_region in loop
04:12
Manual Device Node Creation
03:54
Automatic Device Node Creation - class_create
04:02
Automatic Device Node Creation - device_create
02:48
Example of automatic device node creation
01:54
Quiz 1
11 questions

Introduction
01:46
Registering file_operations with Linux Kernel
01:44
cdev_init vs cdev_alloc
01:27
Linux Kernel Module example of file operations registrations - cdev_alloc
03:14
Linux Kernel Module example of file operations registrations - cdev_init
02:33
Preview04:25
Walkthrough of drivers/char/mem.c
02:42
How many times open and release will be called in case of fork
04:16
How many times open and release will be called in case of multiple processes
01:27
struct file
03:14
Example of struct file
02:27
struct inode
03:12
Example of struct inode
02:33
Example of struct inode vs struct file
03:28
What happens when i print user space buffer in write function
05:27
Accessing user space buffer in Kernel space
02:26
copy_from_user
02:58
What happens when i pass NULL ptr in write system call
01:19
copy_to_user
01:41
put_user
04:11
get_user
02:14
Passing structure from user space to kernel space and vice versa
02:47
Can i pass user variables on heap to kernel driver
01:52
Passing structure with one member from stack and other in heap
02:29
Kernel utility to print dev_t - print_dev_t, format_dev_t
03:53
Can i use strlen in kernel space
04:14
strnlen_user
02:30
Solution to passing structure with one member in stack and other in heap
03:16
Problem in character driver when we read character by character
02:33
Adding offset support in read and write implementation
05:44
Updated logic to read/write bytes less than requested/available
03:51
Adding lseek support
02:17
Creating multiple device nodes
03:52
Preview03:32
Adding support for private data
02:25
What happens when i call write from user space
04:26

Introduction
03:54
Ioctl example - BLKGETSIZE
03:13
Ioctl example - BLKGETSIZE64
01:16
Ioctl driver method - unlocked_ioctl
03:26
Adding three ioctls in kernel driver
03:24
Symbolic names to ioctls commands
01:58
Defining ioctl commands
06:07
C Example of ioctl macros
01:52
Macros to decode information from ioctl command
01:59
Updated driver code using ioctl macros
01:59
What should be the return value if unsupported command is sent from user space
01:34
access_ok macro
02:25
Updated driver code using access_ok macro
02:32
Fail scenarios of access_ok
02:23
What happens when we pass a different size in ioctl command
02:41
compat_ioctl
06:05
Issues when 32-bit process trying to perform ioctl command
06:21
Sending a signal from module to process
03:39

How many times a device driver is being used by application
02:34
Allow only one process to use the device file at a time
04:59
Restricting access to a single user at a time
05:59
Capabilities
05:19
Example of using capabilities - cap_dac_override
03:15
Example of using capabilities - cap_sys_module
03:14
Example of using capabilities - cap_sys_admin
02:55
Open Flags
05:11
What happens if I don't call close and process terminates
01:47

Linux Trainer

Trainer at Linux Weekend Learning

4.0 Instructor Rating
394 Reviews
7,041 Students
16 Courses

I have been working on Linux for more than 7 years. I have seen many people still lack their skills on Linux. So, i am working on courses for Linux which will make them Learn Linux in an easy way. The agenda of my courses will be more practical and less theoretical. Show more examples and you will easily grab the concepts.

This course includes:

Character Device Drivers in deep

What you'll learn

Requirements

Description

Who this course is for:

Course content

Instructor

This course includes:

Character Device Drivers in deep

What you'll learn

Requirements

Description

Who this course is for:

Course content

Introduction22 lectures • 53min

File Operations36 lectures • 1hr 48min

IOCTL18 lectures • 57min

Access Control and Capabilities9 lectures • 35min

Misc Driver2 lectures • 7min

Resources1 lecture • 1min

Instructor