ldd3 scullc编译出错的解决方法

错误1：

make -C /lib/modules/3.2.0-23-generic-pae/build M=/home/yangql/ldd3/code/scullc LDDINC=/home/yangql/ldd3/code/scullc modules
make[1]: Entering directory `/usr/src/linux-headers-3.2.0-23-generic-pae'
scripts/Makefile.build:49: *** CFLAGS was changed in "/home/yangql/ldd3/code/scullc/Makefile". Fix it to use ccflags-y. Stop.
make[1]: *** [_module_/home/yangql/ldd3/code/scullc] Error 2
make[1]: Leaving directory `/usr/src/linux-headers-3.2.0-23-generic-pae'
make: *** [modules] Error 2

修改Makefile，将CFLAGS修改为EXTRA_CFLAGS

错误2：

make -C /lib/modules/3.2.0-23-generic-pae/build M=/home/yangql/ldd3/code/scullc LDDINC=/home/yangql/ldd3/code/scullc modules
make[1]: Entering directory `/usr/src/linux-headers-3.2.0-23-generic-pae'
  CC [M] /home/yangql/ldd3/code/scullc/main.o
/home/yangql/ldd3/code/scullc/main.c:18:26: fatal error: linux/config.h: No such file or directory
compilation terminated.
make[2]: *** [/home/yangql/ldd3/code/scullc/main.o] Error 1
make[1]: *** [_module_/home/yangql/ldd3/code/scullc] Error 2
make[1]: Leaving directory `/usr/src/linux-headers-3.2.0-23-generic-pae'
make: *** [modules] Error 2

去掉头文件config.h
错误3：

make -C /lib/modules/3.2.0-23-generic-pae/build M=/home/yangql/ldd3/code/scullc LDDINC=/home/yangql/ldd3/code/scullc modules
make[1]: Entering directory `/usr/src/linux-headers-3.2.0-23-generic-pae'
  CC [M] /home/yangql/ldd3/code/scullc/main.o
/home/yangql/ldd3/code/scullc/main.c:52:1: error: unknown type name ???kmem_cache_t???
/home/yangql/ldd3/code/scullc/main.c: In function ???scullc_write???:
/home/yangql/ldd3/code/scullc/main.c:247:3: warning: passing argument 1 of ???kmem_cache_alloc??? from incompatible pointer type [enabled by default]

这是因为kmem_cache_t结构被换成了kmem_cache。而kmem_cache定义在和。但是你并不需要包含这两个文件中的一个。因为会根据CONFIG_SLUB等来判断具体包含，还是。故例程中需要将

kmem_cache_t *scullc_cache;
改为：
struct kmem_cache *scullc_cache;

错误4：

CC [M] /home/yangql/ldd3/code/scullc/main.o
/home/yangql/ldd3/code/scullc/main.c: In function ???scullc_defer_op???:
/home/yangql/ldd3/code/scullc/main.c:440:54: error: macro "INIT_WORK" passed 3 arguments, but takes just 2
/home/yangql/ldd3/code/scullc/main.c:440:2: error: ???INIT_WORK??? undeclared (first use in this function)
/home/yangql/ldd3/code/scullc/main.c:440:2: note: each undeclared identifier is reported only once for each function it appears in
/home/yangql/ldd3/code/scullc/main.c:441:2: warning: passing argument 1 of ???schedule_delayed_work??? from incompatible pointer type [enabled by default]

修改

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

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

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

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

错误5：
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/home/yangql/ldd3/code/scullc/main.c: In function ???scullc_init???:
/home/yangql/ldd3/code/scullc/main.c:561:4: 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。

错误6：
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/home/yangql/ldd3/code/scullc/main.c:470:2: error: unknown field ???ioctl??? specified in initializer

修改.ioctl = scullc_ioctl, 为.unlocked_ioctl = scullc_ioctl, 同时将scullc_ioctl的返回值修改为

long scullc_ioctl (struct file *filp, unsigned int cmd, unsigned long arg)



处理警告信息

/home/yangql/ldd3/code/scullc/main.c: In function ???scullc_defer_op???:
/home/yangql/ldd3/code/scullc/main.c:440:2: warning: assignment from incompatible pointer type [enabled by default]
/home/yangql/ldd3/code/scullc/main.c: At top level:
/home/yangql/ldd3/code/scullc/main.c:470:2: warning: initialization from incompatible pointer type [enabled by default]
/home/yangql/ldd3/code/scullc/main.c:470:2: warning: (near initialization for ???scullc_fops.unlocked_ioctl???) [enabled by default]
/home/yangql/ldd3/code/scullc/main.c:473:2: warning: initialization from incompatible pointer type [enabled by default]
/home/yangql/ldd3/code/scullc/main.c:473:2: warning: (near initialization for ???scullc_fops.aio_read???) [enabled by default]
/home/yangql/ldd3/code/scullc/main.c:474:2: warning: initialization from incompatible pointer type [enabled by default]
/home/yangql/ldd3/code/scullc/main.c:474:2: warning: (near initialization for ???scullc_fops.aio_write???) [enabled by default]

在2.6.22版本以后的内核中，INIT_WORK已经做了大幅度的修改 ，INIT_WORK现在使用2个参数，去掉了最后一个data参数，传入func的声明也有所变化。如下所示：
INIT_WORK(struct work_struct *work, void (*function)(struct work_struct *));
INIT_DELAYED_WORK(struct delayed_work *work, void (*function)(struct work_struct *));
这时function以INIT_WROK中的第一参数work作为参数。因此在使用时需要将的struct work_struct *work加入到data所在的数据结构。这里需要注意在引用INIT_DELAYED_WORK时struct work_struct这个结构自身的改动，work_struct结构体包含于delayed_work结构体中，如下：
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struct delayed_work {
        struct work_struct work;
        struct timer_list timer;
}

因此函数scullc_do_deferred_op修改如下：

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

由于aio_read和aio_write函数有改变，最新的声明为：
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ssize_t (*aio_read) (struct kiocb *iocb, const struct iovec *iov, unsigned long niov, loff_t pos);
ssize_t (*aio_write) (struct kiocb *iocb, const struct iovec *iov, unsigned long niov, loff_t pos);

根据上面的声明修改下面的函数为

static ssize_t scullc_aio_read(struct kiocb *iocb, const struct iovec *iov, unsigned long niov, loff_t pos)
{
    return scullc_defer_op(0, iocb, iov, niov, pos);
}

static ssize_t scullc_aio_write(struct kiocb *iocb, const struct iovec *iov,unsigned long niov, loff_t pos)
{
    return scullc_defer_op(1, iocb, iov, niov, pos);
}

static int scullc_defer_op(int write, struct kiocb *iocb, const struct iovec *iov, unsigned long niov, loff_t pos)
{
    struct async_work *stuff;
    int result;

     /* Copy now while we can access the buffer */
     if (write)
         result = scullc_write(iocb->ki_filp, (char *)(iov->iov_base), iov->iov_len, &pos);
    else
         result = scullc_read(iocb->ki_filp, (char *)(iov->iov_base), iov->iov_len, &pos);

    /* If this is a synchronous IOCB, we return our status now. */
    if (is_sync_kiocb(iocb))
        return result;

     /* Otherwise defer the completion for a few milliseconds. */
    stuff = kmalloc (sizeof (*stuff), GFP_KERNEL);
    if (stuff == NULL)
        return result; /* No memory, just complete now */
    stuff->iocb = iocb;
    stuff->result = result;
    INIT_DELAYED_WORK(&(stuff->delayed_work), scullc_do_deferred_op);
    schedule_delayed_work(&(stuff->delayed_work), HZ/100);
    return -EIOCBQUEUED;
}