DMA是数据传输的快速通道,不经过CPU,只占用总线周期。主要是根据DATASHEET配置DMA
现写一驱动程序:设置需要用到DMA通道传输数据的源、目的、长度等参数,让DMA自行传输,
传输完毕后,比较源、目的的最终数据,检验是否传输完整并正确。
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/device.h>
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#include <linux/cdev.h>
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#include <linux/fs.h>
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#include <linux/sched.h>
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#include <linux/wait.h>
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#include <linux/dma-mapping.h>
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#include <linux/string.h>
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#include <linux/interrupt.h>
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#include <mach/irqs.h>
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#define BUF_SZ 512*1024
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#define NO_DMA 0
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#define USE_DMA 1
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#define DMA0_BASE_ADDR 0x4B000000
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#define DMA1_BASE_ADDR 0x4B000040
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#define DMA2_BASE_ADDR 0x4B000080
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#define DMA3_BASE_ADDR 0x4B0000C0
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struct dma_regs {
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unsigned long disrc;
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unsigned long disrcc;
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unsigned long didst;
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unsigned long didstc;
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unsigned long dcon;
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unsigned long dstat;
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unsigned long dcsrc;
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unsigned long dcdst;
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unsigned long dmasktrig;
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};
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static DECLARE_WAIT_QUEUE_HEAD(dma_waith);
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volatile struct dma_regs *dma_regs;
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static dma_addr_t src_phys;
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static dma_addr_t dst_phys;
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static char *src;
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static char *dst;
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static struct cdev cdev;
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static int major;
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static struct class *cls;
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static volatile int ev_dma = 0;
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static int dma_ioctl (struct inode *inode, struct file *filp, unsigned int cmd, unsigned long arg)
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{
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int i;
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memset(src, 1, BUF_SZ);
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memset(dst, 0, BUF_SZ);
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switch (cmd) {
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case NO_DMA:
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{
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for(i=0; i<BUF_SZ; i++)
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dst[i] = src[i];
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if (0 == memcmp(src, dst, BUF_SZ))
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printk("(NO_DMA)Success to memcpy from source to destination.n");
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else
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printk("(NO_DMA)Failed to memcpy from source to destination.n");
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}
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break;
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case USE_DMA:
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{
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ev_dma = 1;
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/* 设置DMA相关寄存器 */
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* DISRC[30:0]= src_phys:base address of source data to transfer
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* DIDST[30:0]= dst_phys:base address of destination for the transfer
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* DISRCC[1] = 0 : the source is in the system bus (AHB)
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* DISRCC[0] = 0 : select the address increment.
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* DIDSTC[2] = 0 : interrupt will occur when TC reaches 0
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* DIDSTC[1] = 0 : the destination is in the system bus (AHB)
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* DIDSTC[0] = 0 : select the address increment
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* DCON[31] = 0 : demand mode will be selected
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* DCON[30] = 1 : DREQ and DACK are synchronized to HCLK (AHB clock)
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* DCON[29] = 1 : interrupt request is generated when all the transfer is done
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* DCON[28] = 0 : a unit transfer is performed
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* DCON[27] = 1 : whole service mode
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* DCON[26:24]=000: select DMA request source for each DMA
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* DCON[23] = 0 : S/W request mode is selected
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* DCON[22] = 0 : auto reload
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* DCON[21:20]= 00: data size(byte) to be transferred.
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* DCON[19:0] = BUF_SZ : initial transfer count
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* DMASKTRIG[1] = 1 : DMA channel is turned on
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* DMASKTRIG[0] = 1 : trigger the DMA channel in S/W request mode.
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*/
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dma_regs->disrc = src_phys;
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dma_regs->didst = dst_phys;
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dma_regs->disrcc = (0<<1)|(0<<0);
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dma_regs->didstc = (0<<2)|(0<<1)|(0<<0);
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dma_regs->dcon = (0<<31)|(1<<30)|(1<<29)|(0<<28)|(1<<27)|(0<<24)|
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(0<<23)|(0<<22)|(0<<20)|(BUF_SZ<<0);
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/* 启动DMA */
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dma_regs->dmasktrig = (1<<1)|(1<<0);
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/* 休眠等待数据传输 */
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wait_event_interruptible(dma_waith, ev_dma);
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if (0 == memcmp(src, dst, BUF_SZ))
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printk("(USE_DMA)Success to memcpy from source to destination.n");
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else
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printk("(USE_DMA)Failed to memcpy from source to destination.n");
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}
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break;
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}
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return 0;
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}
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static struct file_operations fops =
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{
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.ioctl = dma_ioctl,
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};
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static irqreturn_t mydma_irq(int irq, void *dat)
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{
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ev_dma = 1;
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/* 数据传输完毕唤醒队列 */
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wake_up_interruptible(&dma_waith);
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return IRQ_HANDLED;
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}
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static int mydma_init(void)
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{
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dev_t devt;
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/* 分配源、目的 缓冲区 */
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src = dma_alloc_writecombine(NULL, BUF_SZ, &src_phys,GFP_KERNEL);
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if (NULL == src)
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{
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printk("src-dma alloc failed!n");
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return -ENOMEM;
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}
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dst = dma_alloc_writecombine(NULL, BUF_SZ, &dst_phys, GFP_KERNEL);
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if (NULL == dst)
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{
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printk("dst-dma alloc failedn");
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dma_free_writecombine(NULL, BUF_SZ, src, src_phys);
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return -ENOMEM;
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}
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/* 动态申请字符设备区域 */
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alloc_chrdev_region(&devt, 0, 1, "mydma");
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/* MAJOR得到主设备号*/
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major = MAJOR(devt);
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/* 初始化并添加字符设备 */
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cdev_init(&cdev, &fops);
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cdev_add(&cdev, devt, 1);
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/* 创建类 */
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cls = class_create(THIS_MODULE, "mycls");
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/* 创建类下的设备 */
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device_create(cls, NULL, devt, NULL, "mydma");
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/* 映射DMA寄存器 */
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dma_regs = ioremap(DMA3_BASE_ADDR, sizeof(struct dma_regs));
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/* 申请DMA中断*/
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request_irq(IRQ_DMA3, mydma_irq, 0, "dma3", 1);
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return 0;
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}
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static void mydma_exit(void)
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{
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free_irq(IRQ_DMA3, 1);
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iounmap(dma_regs);
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device_destroy(cls, MKDEV(major, 0));
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class_destroy(cls);
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cdev_del(&cdev);
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unregister_chrdev_region(MKDEV(major, 0), 1);
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dma_free_writecombine(NULL, BUF_SZ, src, src_phys);
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dma_free_writecombine(NULL, BUF_SZ, dst, dst_phys);
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return ;
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}
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module_init(mydma_init);
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module_exit(mydma_exit);
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MODULE_LICENSE("GPL");
测试程序:
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#include <stdio.h>
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#include <string.h>
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#include <fcntl.h>
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#define NO_DMA 0
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#define USE_DMA 1
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int main(int argc, char *argv[])
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{
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int cmd, fd;
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if (argc != 2)
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{
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printf("%s n", argv[0]);
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return -1;
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}
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fd = open("/dev/mydma", O_RDWR);
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if(fd < 0)
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printf("can not open /dev/mydman");
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if(0 == strcmp(argv[1], "nodma"))
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{
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cmd = NO_DMA;
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}
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else if(0 == strcmp(argv[1], "usedma"))
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{
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cmd = USE_DMA;
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}
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else
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{
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printf("%s n", argv[0]);
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return -1;
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}
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while(1)
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{
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ioctl(fd, cmd);
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}
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return 0;
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}
2012-05-10 16:05 发表于百度空间,今搬至CU。
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