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我在閱讀一個簡單的驅(qū)動代碼時,有一個地方看不懂,在程序的開頭定義了一個結(jié)構(gòu)體類型的指針struct mem_dev *mem_devp,可在程序中卻出現(xiàn)了memdevp,i取0和1,這在程序中有定義,mem_dev【i】算是指針數(shù)組嗎,如果是,怎么沒在程序的開頭定義呢,再說指針數(shù)組在這里又起什么用呢?程序代碼如下:(紅色字體是我不懂的地方)
#include <linux/module.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <asm/io.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include "memdev.h"
static mem_major = MEMDEV_MAJOR;
module_param(mem_major, int, S_IRUGO);
struct mem_dev *mem_devp; /*設(shè)備結(jié)構(gòu)體指針*/
struct cdev cdev;
/*設(shè)備驅(qū)動模塊加載函數(shù)*/
static int memdev_init(void)
{
int result;
int i;
dev_t devno = MKDEV(mem_major, 0);
/* 靜態(tài)申請設(shè)備號*/
if (mem_major)
result = register_chrdev_region(devno, 2, "memdev");
else /* 動態(tài)分配設(shè)備號 */
{
result = alloc_chrdev_region(&devno, 0, 2, "memdev");
mem_major = MAJOR(devno);
}
if (result < 0)
return result;
/*初始化cdev結(jié)構(gòu)*/
cdev_init(&cdev, &mem_fops);
cdev.owner = THIS_MODULE;
cdev.ops = &mem_fops;
/* 注冊字符設(shè)備 */
cdev_add(&cdev, MKDEV(mem_major, 0), MEMDEV_NR_DEVS);
/* 為設(shè)備描述結(jié)構(gòu)分配內(nèi)存*/
mem_devp = kmalloc(MEMDEV_NR_DEVS * sizeof(struct mem_dev), GFP_KERNEL);
if (!mem_devp) /*申請失敗*/
{
result = - ENOMEM;
goto fail_malloc;
}
memset(mem_devp, 0, sizeof(struct mem_dev));
/*為設(shè)備分配內(nèi)存*/
for (i=0; i < MEMDEV_NR_DEVS; i++)
{
mem_devp.size = MEMDEV_SIZE;
mem_devp.data = kmalloc(MEMDEV_SIZE, GFP_KERNEL);
memset(mem_devp.data, 0, MEMDEV_SIZE);
}
return 0;
fail_malloc:
unregister_chrdev_region(devno, 1);
return result;
}
/*模塊卸載函數(shù)*/
static void memdev_exit(void)
{
cdev_del(&cdev); /*注銷設(shè)備*/
kfree(mem_devp); /*釋放設(shè)備結(jié)構(gòu)體內(nèi)存*/
unregister_chrdev_region(MKDEV(mem_major, 0), 2); /*釋放設(shè)備號*/
}
MODULE_AUTHOR("David Xie");
MODULE_LICENSE("GPL");
module_init(memdev_init);
module_exit(memdev_exit); |
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