linux.device.drivers

sailor_973

linux.device.drivers
=====================

1. modules
        -- insmod, insert a module in kernel, and run the init function which is specified            by
                module_init(<init func>);

        -- rmmod, remove a module from kernel, and run the exit function which is specified                       by
                module_exit(<exit func>);

modules vs applications
        All event-driven applications can be implemented as modules.
        module's exit function must undo everything the init function built up.(i.e. free         resources)
        But application may not always do those all.

        A module, on the other hand, is linked only to the kernel, and the only functions it can call are the ones exported by the kernel;
        an application can call functions it doesn't define, only if it is defined in shared         lib.

2.

printk() is defined in kernel, but it do not support floating-point.
因为module没有lib可用，所以不要include那些常用的head file, i.e. stdarg.h
all head file can be included in module, is include/linux and include/asm

Concurrency in the Kernel
kernel code and driver code must be reentrant(可重入的)

'current' is the global item that can be used in kernel programing.
I.e.
printk(KERN_INFO "The process is \"%s\" (pid %i)\n",

        current->comm, current->pid);

Kernel's stack size is only 4KB.
So if you need larger structures, just get memory by malloc instead of apply great buffer by automatic variables.

obj-m := module.o

module-objs := file1.o file2.o

all system calls has a same prefix: 'sys_'

runlover

楼主这篇东西让人意犹未尽啊，好像没讲清楚。