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 driver’s 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 > dev/scull0

7. Examples-Hello World • #define MODULE • #include <linux/module.h> • int init_module (void) {printk(“<1>Hello, World\n”); return 0} • void cleanup_module {printk(“<1>Goodbye, cruel World\n”);}

8. Examples-Scull • #define MODULE, __KERNEL__ • #include <linux/module.h>…. • 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