linux设备驱动程序3-字符驱动

1、函数container_of()根据一个结构体变量中的一个域成员变量的指针来获取指向整个结构体变量的指针
contain定义在中，原型如下：
/**
 * container_of - cast a member of a structure out to the containing structure
 * @ptr:    the pointer to the member.
 * @type:    the type of the container struct this is embedded in.
 * @member:    the name of the member within the struct.
 *
 */
#define container_of(ptr, type, member) ({            \
    const typeof( ((type *)0)->member ) *__mptr = (ptr);    \
    (type *)( (char *)__mptr - offsetof(type,member) );})
其中offsetof()定义在中，原型如下：
#ifdef __compiler_offsetof
#define offsetof(TYPE,MEMBER) __compiler_offsetof(TYPE,MEMBER)
#else
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
#endif
例如：
int scull_open(struct inode *inode, struct file *filp)
{
struct scull_dev *dev; /* device information */
//已知inode->i_cdev是struct scull_dev中成员cdev的地址，可得到inode->i_cdev所在的scull_dev类型变量的地址。
dev = container_of(inode->i_cdev, struct scull_dev, cdev);
filp->private_data = dev; /* for other methods */
/* now trim to 0 the length of the device if open was write-only
*/
if ( (filp->f_flags & O_ACCMODE) == O_WRONLY)
{
scull_trim(dev); /* ignore errors */
}
return 0; /* success */
}
2、strace 工具：用来跟踪进程执行时的系统调用和所接收的信号
[chenyun@pon platform]$ strace ls
execve("/bin/ls", ["ls"], [/* 30 vars */]) = 0
brk(0)                                  = 0x9099000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=62697, ...}) = 0
mmap2(NULL, 62697, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7f0a000
close(3)                                = 0
open("/lib/librt.so.1", O_RDONLY)       = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\200\350\270\0004\0\0\0"..., 512) = 512
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f09000
fstat64(3, {st_mode=S_IFREG|0755, st_size=48156, ...}) = 0
mmap2(0xb8d000, 33324, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb8d000
mmap2(0xb94000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x7) = 0xb94000
close(3)                                = 0
open("/lib/libacl.so.1", O_RDONLY)      = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0@\222\267\0004\0\0\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=25660, ...}) = 0
mmap2(0xb78000, 27008, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb78000
mmap2(0xb7e000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x5) = 0xb7e000
close(3)                                = 0
open("/lib/libselinux.so.1", O_RDONLY)  = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\240\265\271\0004\0\0\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=93508, ...}) = 0
mmap2(0xb98000, 97120, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb98000
mmap2(0xbae000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x15) = 0xbae000
close(3)                                = 0
open("/lib/libc.so.6", O_RDONLY)        = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\0\20\236\0004\0\0\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=1710436, ...}) = 0
mmap2(0x9cb000, 1426884, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x9cb000
mmap2(0xb22000, 12288, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x157) = 0xb22000
mmap2(0xb25000, 9668, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb25000
close(3)                                = 0
open("/lib/libpthread.so.0", O_RDONLY)  = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0p\10\266\0004\0\0\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=137944, ...}) = 0
mmap2(0xb5c000, 102884, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb5c000
mmap2(0xb72000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x15) = 0xb72000
mmap2(0xb74000, 4580, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb74000
close(3)                                = 0
open("/lib/libattr.so.1", O_RDONLY)     = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\200+\24\0004\0\0\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0775, st_size=15780, ...}) = 0
mmap2(0x142000, 17056, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x142000
mmap2(0x146000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x3) = 0x146000
close(3)                                = 0
open("/lib/libdl.so.2", O_RDONLY)       = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0p\252\262\0004\0\0\0"..., 512) = 512
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f08000
fstat64(3, {st_mode=S_IFREG|0755, st_size=20668, ...}) = 0
mmap2(0xb2a000, 16504, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb2a000
mmap2(0xb2d000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x2) = 0xb2d000
close(3)                                = 0
open("/lib/libsepol.so.1", O_RDONLY)    = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0@O\273\0004\0\0\0"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=245376, ...}) = 0
mmap2(0xbb2000, 285024, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xbb2000
mmap2(0xbed000, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x3b) = 0xbed000
mmap2(0xbee000, 39264, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xbee000
close(3)                                = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f07000
set_thread_area({entry_number:-1 -> 6, base_addr:0xb7f078e0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0
mprotect(0xb94000, 4096, PROT_READ)     = 0
mprotect(0xb22000, 8192, PROT_READ)     = 0
mprotect(0xb72000, 4096, PROT_READ)     = 0
mprotect(0x9c7000, 4096, PROT_READ)     = 0
mprotect(0xb2d000, 4096, PROT_READ)     = 0
munmap(0xb7f0a000, 62697)               = 0
set_tid_address(0xb7f07928)             = 9780
set_robust_list(0xb7f07930, 0xc)        = 0
futex(0xbf879bb4, FUTEX_WAKE_PRIVATE, 1) = 0
rt_sigaction(SIGRTMIN, {0xb60400, [], SA_SIGINFO}, NULL, 8) = 0
rt_sigaction(SIGRT_1, {0xb60300, [], SA_RESTART|SA_SIGINFO}, NULL, 8) = 0
rt_sigprocmask(SIG_UNBLOCK, [RTMIN RT_1], NULL, 8) = 0
getrlimit(RLIMIT_STACK, {rlim_cur=10240*1024, rlim_max=RLIM_INFINITY}) = 0
uname({sys="Linux", node="pon.twsh.com", ...}) = 0
access("/etc/selinux/", F_OK)           = 0
brk(0)                                  = 0x9099000
brk(0x90ba000)                          = 0x90ba000
open("/etc/selinux/config", O_RDONLY|O_LARGEFILE) = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=511, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f19000
read(3, "# This file controls the state o"..., 4096) = 511
read(3, "", 4096)                       = 0
close(3)                                = 0
munmap(0xb7f19000, 4096)                = 0
open("/proc/mounts", O_RDONLY|O_LARGEFILE) = 3
fstat64(3, {st_mode=S_IFREG|0444, st_size=0, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f19000
read(3, "rootfs / rootfs rw 0 0\n/dev/root"..., 1024) = 677
read(3, "", 1024)                       = 0
close(3)                                = 0
munmap(0xb7f19000, 4096)                = 0
open("/usr/lib/locale/locale-archive", O_RDONLY|O_LARGEFILE) = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=56426176, ...}) = 0
mmap2(NULL, 2097152, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7d07000
close(3)                                = 0
ioctl(1, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon echo ...}) = 0
ioctl(1, TIOCGWINSZ, {ws_row=61, ws_col=132, ws_xpixel=0, ws_ypixel=0}) = 0
open(".", O_RDONLY|O_NONBLOCK|O_LARGEFILE|O_DIRECTORY) = 3
fcntl64(3, F_SETFD, FD_CLOEXEC)         = 0
getdents64(3, /* 9 entries */, 32768)   = 240
getdents64(3, /* 0 entries */, 32768)   = 0
close(3)                                = 0
fstat64(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 44), ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f19000
write(1, "build  docs  make  Makefile  src"..., 40build  docs  make  Makefile  src  tools
) = 40
close(1)                                = 0
munmap(0xb7f19000, 4096)                = 0
exit_group(0)                           = ?
[chenyun@pon platform]$
[chenyun@pon platform]$
更详细的说明见如下链接：http://www.cnblogs.com/bangerlee/archive/2012/02/20/2356818.html
3、awk命令: 简单来说awk就是把文件逐行的读入，以空格为默认分隔符将每行切片，切开的部分再进行各种分析处理
语法：

awk '{pattern + action}' {filenames} awk工作流程是这样的：读入有'\n'换行符分割的一条记录，然后将记录按指定的域分隔符划分域，填充域， $0则表示所有域,$1表示第一个域,$n表示第n个域。默认域分隔符是"空白键" 或 "[tab]键",所以$1表示登录用户，$3表示登录用户ip,以此类推。 

[chenyun@pon platform]$ ll
total 28
drwxr-xr-x  3 chenyun chenyun 4096 Nov 24 11:17 build
drwxr-xr-x  7 chenyun chenyun 4096 Nov  4 11:21 docs
drwxr-xr-x  3 chenyun chenyun 4096 Nov  4 11:19 make
-rwxr-xr-x  1 chenyun chenyun 6961 Nov  4 11:21 Makefile
drwxr-xr-x 10 chenyun chenyun 4096 Nov  4 11:20 src
drwxr-xr-x  8 chenyun chenyun 4096 Nov  4 11:19 tools
[chenyun@pon platform]$
[chenyun@pon platform]$

[chenyun@pon platform]$
[chenyun@pon platform]$ ll |awk '{print $1"\t"$9}'
total
drwxr-xr-x      build
drwxr-xr-x      docs
drwxr-xr-x      make
-rwxr-xr-x      Makefile
drwxr-xr-x      src
drwxr-xr-x      tools
[chenyun@pon platform]$
例子：读取proc/device中scull的设备号
#!/bin/sh
module="scull"
major=$(awk "\\$2==\"$module\" {print \\$1}" /proc/devices)
更详细的参考见：http://www.cnblogs.com/ggjucheng/archive/2013/01/13/2858470.html