linux内核驱动初始化流程,linux 内核设备驱动初始化的实现（转）

太过爱你忘了你带给我的痛 2023-01-20 03:00 254阅读 0赞

解压,打印“Uncompressing Linux...”，调用gunzip()，打印"done, booting the kernel."然后call\_kernel,执行解压后的kernel,经/arch//kernel/head.S调用start\_kernel转入体系结构无关的通用C代码，在start\_kernel()中完成了一系列系统初始化，设备及驱动的注册即在此时完成：

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asmlinkage void \_\_init start\_kernel(void)

char \* command\_line;

extern struct kernel\_param \_\_start\_\_\_param\[\], \_\_stop\_\_\_param\[\];

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printk(KERN\_NOTICE "Kernel command line: %s\\n", saved\_command\_line);

//打印内核命令行

parse\_early\_param();

parse\_args("Booting kernel", command\_line, \_\_start\_\_\_param, \_\_stop\_\_\_param - \_\_start\_\_\_param,

&unknown\_bootoption);

//解析由BOOT传递的启动参数

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/\* Do the rest non-\_\_init'ed, we're now alive \*/

rest\_init();

start\_kernel()中的函数rest\_init()将创建第一个核心线程kernel\_thread(init, NULL, CLONE\_FS | CLONE\_SIGHAND)，调用init()函数：

static int init(void \* unused)－－－－－－－－－－－－－－－－－－－

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do\_basic\_setup();

/\*

\* We try each of these until one succeeds.

\* The Bourne shell can be used instead of init if we are

\* trying to recover a really broken machine.

\*/

if (execute\_command) \{ //判断在启动时是否指定了init参数

//如果指定则执行用户init进程，成功将不会返回

run\_init\_process(execute\_command);

printk(KERN\_WARNING "Failed to execute %s. Attempting " "defaults...\\n", execute\_command);

/\* 如果没有指定init启动参数，则查找下面的目录init进程,成功将不会返回，否则打印出错信息 \*/

run\_init\_process("/sbin/init");

run\_init\_process("/etc/init");

run\_init\_process("/bin/init");

run\_init\_process("/bin/sh");

panic("No init found. Try passing init= option to kernel.");

继而调用函数do\_basic\_setup()(此时与体系结构相关的部分已经初始化完了,现在开始初始化设备了)：

/\*

\* Ok, the machine is now initialized. None of the devices \* have been touched yet, but the CPU subsystem is up and \* running, and memory and process management works.

\* Now we can finally start doing some real work..

\*/

static void \_\_init do\_basic\_setup(void)－－－－－－－－－－－－－－－－－

/\* drivers will send hotplug events \*/

init\_workqueues();

usermodehelper\_init();

driver\_init(); //建立设备模型子系统

\#ifdef CONFIG\_SYSCTL

sysctl\_init();

\#endif

/\* Networking initialization needs a process context \*/

sock\_init();

do\_initcalls(); //系统初始化(包括设备，文件系统，内核模块等)

下面分析driver\_init():

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/\*\*

\* driver\_init - initialize driver model.

\* Call the driver model init functions to initialize their

\* subsystems. Called early from init/main.c.

\*/

void \_\_init driver\_init(void)

/\* These are the core pieces \*/

devices\_init();

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int \_\_init devices\_init(void)

return subsystem\_register(&devices\_subsys);

subsystem\_register():

buses\_init();

classes\_init();

firmware\_init();

/\* These are also core pieces, but must come after the \* core core pieces.

\*/

platform\_bus\_init();

system\_bus\_init();

cpu\_dev\_init();

memory\_dev\_init();

attribute\_container\_init();

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extern initcall\_t \_\_initcall\_start\[\], \_\_initcall\_end\[\];

static void \_\_init do\_initcalls(void)

initcall\_t \*call;

int count = preempt\_count();

for (call = \_\_initcall\_start; call < \_\_initcall\_end; call++) \{

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(\*call)(); //调用一系列初始化函数

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\_\_initcall\_start和\_\_initcall\_end界定了存放初始化函数指针区域的起始地址，即从\_\_initcall\_start开始到\_\_initcall\_end结束的区域中存放了指向各个初始化函数的函数指针。 由 (\*call)()完成各个部分的初始化工作，且便于扩充。具体实现如下：－－－－－－－－－－－－－－－－－\_\_initcall\_start = .;

\*(.initcall1.init) \*(.initcall2.init) \*(.initcall3.init) \*(.initcall4.init) \*(.initcall5.init) \*(.initcall6.init) \*(.initcall7.init) \_\_initcall\_end = .;

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\#ifndef MODULE /\*如果驱动模块静态编译进内核\*/

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/\* initcalls are now grouped by functionality into separate

\* subsections. Ordering inside the subsections is determined \* by link order. \* For backwards compatibility, initcall() puts the call in \* the device init subsection.

\*/

\#define \_\_define\_initcall(level,fn) \\

static initcall\_t \_\_initcall\_\#\#fn \_\_attribute\_used\_\_ \\

\_\_attribute\_\_((\_\_section\_\_(".initcall" level ".init"))) = fn

\#define core\_initcall(fn) \_\_define\_initcall("1",fn) \#define postcore\_initcall(fn) \_\_define\_initcall("2",fn) \#define arch\_initcall(fn) \_\_define\_initcall("3",fn)

//此处初始化了设备

/\*－－－－eg：arch\_initcall(at91sam9261\_device\_init)－－－

static int \_\_init at91sam9261\_device\_init(void)

at91\_add\_device\_udc();

at91\_add\_device\_dm9000();

ebs3\_add\_input\_buttons();

return platform\_add\_devices(at91sam9261\_devices, ARRAY\_SIZE(at91sam9261\_devices));

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\#define subsys\_initcall(fn) \_\_define\_initcall("4",fn) \#define fs\_initcall(fn) \_\_define\_initcall("5",fn) \#define device\_initcall(fn) \_\_define\_initcall("6",fn)

//此处初始化了静态编译的驱动模块

\#define late\_initcall(fn) \_\_define\_initcall("7",fn)

\#define \_\_initcall(fn) device\_initcall(fn)

/\*\*

\* module\_init() - driver initialization entry point

\* @x: function to be run at kernel boot time or module insertion

\* module\_init() will either be called during do\_initcalls (if

\* builtin) or at module insertion time (if a module). There can only \* be one per module.

\*/

\#define module\_init(x) \_\_initcall(x);

//静态编译的驱动模块作为device\_initcall在内核启动就被do\_initcalls

/\*\*

\* module\_exit() - driver exit entry point

\* @x: function to be run when driver is removed

\* module\_exit() will wrap the driver clean-up code

\* with cleanup\_module() when used with rmmod when

\* the driver is a module. If the driver is statically \* compiled into the kernel, module\_exit() has no effect. \* There can only be one per module.

\*/

\#define module\_exit(x) \_\_exitcall(x);

\#else /\* MODULE如果驱动模块动态加载入内核\*/

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/\* Each module must use one module\_init(), or one no\_module\_init \*/

\#define module\_init(initfn) \\

static inline initcall\_t \_\_inittest(void) \\

\{ return initfn; \} \\

int init\_module(void) \_\_attribute\_\_((alias(\#initfn)));

//insmod 是通过系统调用sys\_init\_module(const char \*name\_user, struct module \*mod\_user)

//将动态驱动模块载入到内核空间

/\* This is only required if you want to be unloadable. \*/