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BLOCK DEVICE DRIVER

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BLOCK DEVICE DRIVER

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    1. BLOCK DEVICE DRIVER LAB 12

    2. Linux Device Driver Architecture

    3. Quick Functions Reference #include <Linux/fs.h> int register_blkdev(unsigned int major, const char *name); int unregister_blkdev(unsigned int major, const char *name); struct block_device_operations #include <linux/genhd.h> struct gendisk *alloc_disk(int minors); void add_disk(struct gendisk *gd); void set_capacity(struct gendisk *gd, setor_t sectors); void put_disk(struct gendisk *gd); #include <linux/blkdev.h> #define blk_fs_request(rq) ((rq)->flags & REQ_CMD) request_queue_t blk_init_queue(request_fn_proc *request, spinlock_t *lock); struct request *elv_next_request(request_queue_t *queue); void end_request(struct request *req, int success); #include <mm/vmalloc.h> void *vmalloc(unsigned long size);

    4. Quick Functions Reference (cont’) #include <linux/fs.h> struct block_device_operations struct block_device struct inode #include <linuix/genhd.h> struct gendisk #include <linux/blkdev.h> struct request

    5. struct gendisk

    6. struct block_device

    7. struct block_device_operations

    8. Relationship between these structures

    9. Simple block device driver: sbull Needed files: sbull.c Makefile Driver description: it allocates 10 MB memory space to simulate a ramdisk which is like you insert a disk into the system the ramdisk has only one partition many file operations can be performed on it mkfs, mount, umount, cp, ls, …

    10. Simple block device driver: sbull (cont’) Needed functions: sbull_init() sbull_exit() sbull_open() sbull_release() sbull_request() sbull_transfer()

    11. Source code of sbull.c include and define

    12. Source code of sbull.c (cont’) struct and function prototype:

    13. Source code of sbull.c (cont’) struct Device and open, release methods:

    14. Source code of sbull.c (cont’) sbull_init method:

    15. Source code of sbull.c (cont’) sbull_init method: (cont’)

    16. Source code of sbull.c (cont’) sbull_request method:

    17. Source code of sbull.c (cont’) sbull_transfer method:

    18. Source code of sbull.c (cont’) sbull_exit method and module-related macros:

    19. The Makefile of sbull

    20. LAB 1 Create the simple block device driver and insert into the kernel: make sudo insmod sbull.ko cat /proc/devices | grep sbull

    21. LAB 1 (cont’) Create the device node and mount it: sudo mknod /dev/sbulla b XXX 0 replaces XXX to the major number you get above Ubuntu may create the /dev/sbulla for us sudo mkfs.ext2 /dev/sbulla mkdir temp sudo mount /dev/sbulla temp df

    22. LAB 1 (cont’)

    23. LAB 1 (cont’) Test the read and write abilities: cd temp sudo mkdir HANEL cd .. sudo umount temp mkdir temp2 sudo mount /dev/sbulla temp2 ls temp2

    24. LAB 1 (cont’)

    25. LAB 1 (cont’) Remove the sbull module from the kernel: sudo umount temp2 sudo rmmod sbull Ubuntu will also clear the /dev/sbulla for us

    26. LAB 2 In this exercise, a extended version sbull will be introduced it allocates 10 MB memory space to simulate a ramdisk which is like you insert a disk into the system the ramdisk has 2 partitions (partitionable) many file operations can be performed on it mkfs, mount, umount, cp, ls, …

    27. LAB 2 (cont’) In order to let the sbull able to be partitioned, there are something needed be done: sets SBULL_MINORS to 2 adds new structure member “short users” in sbull_dev adds one new function in sbull_ops structure alters the sbull_open and sbull_release functions

    28. LAB 2 (cont’) The structure method sbull_ioctl():

    29. LAB 2 (cont’) The functions sbull_open and sbull_release:

    30. LAB 2 (cont’) Test the extended sbull modules: make clean make sudo insmod sbull.ko sudo fdisk –H 16 /dev/sbulla

    31. LAB 2 (cont’)

    32. LAB 2 (cont’) Now we have two partitions in the sbull ramdisk Formats they by the following instructions: sudo mkfs.ext2 /dev/sbulla1 sudo mkfs.ext2 /dev/sbulla2 sudo mount /dev/sbulla1 temp sudo mount /dev/sbulla2 temp2 df

    33. LAB 3 Please format the sbull in LAB1 by instruction: sudo mkfs.vfat –F16 /dev/sbulla and observe what happened Try the same instruction executed on the sbulla in LAB2 Based on the LAB2, give me one block device with: 20MB and can be partitioned automatically: you can consult the sbull of LDD here

    34. LAB 3 (cont’)

    35. LAB 3 There are two errors in the sbull of O’Reilly: comment out the #include <linux/config.h> change the line 181 from “end_that_request_last(req);” to “end_that_request_last(req, 1);” if you want to try that one, just type: make sudo insmod sbull.ko ls –al /dev/sbull*

    36. Reference Driver porting: a simple block driver “Linux Device Drivers” 3rd Edition Cross-Referencing Linux Linux Block Device Architecture

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