ldd3 源码编译之 scullc 字符设备驱动

转自：http://blog.chinaunix.net/uid-25381054-id-3261527.html

使用内核版本-linux-3.2

错误1：

 make -C /lib/modules/3.2.0/build M=/home/wrk/works/drivers/ldd3/examples/scullc LDDINC=/home/wrk/works/drivers/ldd3/examples/scullc modules
 make[1]: Entering directory `/home/wrk/works/drivers/linux-kernel/linux-3.2'
 scripts/Makefile.build:49: *** CFLAGS was changed in "/home/wrk/works/drivers/ldd3/examples/scullc/Makefile". Fix it to use ccflags-y. Stop.
 make[1]: *** [_module_/home/wrk/works/drivers/ldd3/examples/scullc] Error 2
 make[1]: Leaving directory `/home/wrk/works/drivers/linux-kernel/linux-3.2'
 make: *** [modules] Error 2

这个错误还比较好解决，像提示的那样在Makefile中用 ccflags-y 替换 CFLAGS 

错误2：

 /home/wrk/works/drivers/ldd3/examples/scullc/main.c:52:1: error: unknown type name ‘kmem_cache_t’

这是因为kmem_cache_t结构被换成了kmem_cache。而kmem_cache定义在<linux/slab_def.h>和<linux/slub_def.h>。但是你并不需要包含这两个文件中的一个。因为<linux/slab.h>会根据CONFIG_SLUB等来判断具体包含<linux/slab_def.h>，还是<linux/slub_def.h>。故例程中需要将

kmem_cache_t *scullc_cache;
改为：
struct kmem_cache *scullc_cache;

错误3：

 /home/wrk/works/drivers/ldd3/examples/scullc/main.c: In function ‘scullc_defer_op’:
 /home/wrk/works/drivers/ldd3/examples/scullc/main.c:437:54: error: macro "INIT_WORK" passed 3 arguments, but takes just 2
 /home/wrk/works/drivers/ldd3/examples/scullc/main.c:437:2: error: ‘INIT_WORK’ undeclared (first use in this function)

这里需要将

 INIT_WORK(&stuff->work, scull_do_deferred_op, stuff);

改为：

 INIT_WORK(&stuff->work, scull_do_deferred_op);

并且将scullc_do_deferred_op函数改为

 static void scullc_do_deferred_op(struct work_struct *p)
 {
         struct async_work *stuff = container_of(p, struct async_work, work);
         aio_complete(stuff->iocb, stuff->result, 0);
         kfree(stuff);
 }

错误4：  

 /home/wrk/works/drivers/ldd3/examples/scullc/main.c:467:2: error: unknown field ‘ioctl’ specified in initializer

这里因为内核接口变化需要将 .ioctl改为 .unlocked_ioctl

错误5：

 /home/wrk/works/drivers/ldd3/examples/scullc/main.c:558:4: error: too many arguments to function ‘kmem_cache_create’

函数kmem_cache_create的原型已经改变：
struct kmem_cache *kmem_cache_create(const char *, size_t, size_t, unsigned long, void (*)(void *));故调用它的时候应该将参数做出相应的改变。需要将最后一个NULL去掉。

下面来解决 warning：

 /home/wrk/works/drivers/ldd3/examples/scullc/main.c: In function ‘scullc_defer_op’:
 /home/wrk/works/drivers/ldd3/examples/scullc/main.c:437:2: warning: assignment from incompatible pointer type [enabled by default]
 /home/wrk/works/drivers/ldd3/examples/scullc/main.c:438:2: warning: passing argument 1 of ‘schedule_delayed_work’ from incompatible pointer type [enabled by default]
 include/linux/workqueue.h:363:12: note: expected ‘struct delayed_work *’ but argument is of type ‘struct work_struct *’
 /home/wrk/works/drivers/ldd3/examples/scullc/main.c: At top level:
 /home/wrk/works/drivers/ldd3/examples/scullc/main.c:467:2: warning: initialization from incompatible pointer type [enabled by default]
 /home/wrk/works/drivers/ldd3/examples/scullc/main.c:467:2: warning: (near initialization for ‘scullc_fops.unlocked_ioctl’) [enabled by default]
 /home/wrk/works/drivers/ldd3/examples/scullc/main.c:470:2: warning: initialization from incompatible pointer type [enabled by default]
 /home/wrk/works/drivers/ldd3/examples/scullc/main.c:470:2: warning: (near initialization for ‘scullc_fops.aio_read’) [enabled by default]
 /home/wrk/works/drivers/ldd3/examples/scullc/main.c:471:2: warning: initialization from incompatible pointer type [enabled by default]
 /home/wrk/works/drivers/ldd3/examples/scullc/main.c:471:2: warning: (near initialization for ‘scullc_fops.aio_write’) [enabled by default]

1.把

 struct async_work {
 struct kiocb *iocb;
 int result;
 struct work_struct work;
 };

改为：

 struct async_work {
 struct kiocb *iocb;
 int result;
 struct delayed_work delayed_work;
 }

然后把：

 INIT_WORK(&stuff->work, scull_do_deferred_op, stuff);
 schedule_delayed_work(&stuff->work, HZ/100);

改为：

 INIT_DELAYED_WORK(&(stuff->delayed_work), scullc_do_deferred_op);
 schedule_delayed_work(&(stuff->delayed_work), HZ/100);

再编译即可通过。