DEVICE DRIVER

1
DEVICE DRIVER

• VINOD KAMATH
• CS691X PROJECT WORK

2
Introduction

• How to write/install device drivers
• Systems, Kernel Programming
• Character, Block and Network devices

3
Tasks involved

• Building and Running modules
• Character device drivers

4
Building device driver module

• Module vs. Applications
• Appln - single task
• Module - register for future
• Compiling and Loading
• ___KERNEL__, MODULE
• insmod,rmmod
• Global var-Symtab
• Do in Kernel space (not User space)
• response time block/network devs

5
Character device drivers

• Scull - Simple Char. Util. for Loading Localities
• Acts on mem. Area as though it is a device
• Demonstrate interface betn. Kernel and Char
  drivers
• n devices for n mem. areas
• Major/Minor no.- (un)register chr_dev

6
Design and implementation of Scull

• File operations/structure
• Device id. By file structure
• Kenerl uses file ops. To access drivers
  functions
• Open and Close
• Initialize device, usage count,
• Memory
• Device-memory Link List
• Read and Write
• Transfer data from Kernel-User
• Testing/Debugging
• cp, cat, dd wls-l gt dev/scull0

7
Examples-Hello World

• define MODULE
• include ltlinux/module.hgt
• int init_module (void) printk(lt1gtHello,
  World\n) return 0
• void cleanup_module printk(lt1gtGoodbye, cruel
  World\n)

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Examples-Scull

• define MODULE, __KERNEL__
• include ltlinux/module.hgt.
• Struct file_operations d0_fops r,w,o,c
• int init_module (void) malloc, reg do_fops
• void cleanup_module (unreg, free...)l

9
Conclusions

• Writing device drivers is not for faint
  heart/Adventure
• Very careful with Kernel codes

10
Future work

• Try Advanced drivers, Scheduling
• Understand principle for multi user