自学教程：C++ sys_read函数代码示例

static int read_eri(const char *path, eri_read_req_type* read_req_ptr, eri_read_rsp_type* read_rsp_ptr){    int read;//	size_t count;    int read_size;//	int ret;    mm_segment_t oldfs;#ifdef DEBUG_ERI    printk(KERN_ERR "%s, UTS ERI READ Test START/n",__func__);#endif    oldfs = get_fs();    set_fs(KERNEL_DS);    memset(eri_buf,0,sizeof(byte) * 1400);    read = sys_open((const char __user *)path, O_RDONLY , 0);    if(read < 0) {#ifdef DEBUG_ERI        printk(KERN_ERR "%s, ERI File Open Fail/n",__func__);#endif        return -1;    } else {#ifdef DEBUG_ERI        printk(KERN_ERR "%s, ERI File Open Success/n",__func__);#endif    }    read_size = 0;    while(sys_read(read, &eri_buf[read_size++], 1) == 1) {}    memcpy(read_rsp_ptr->eri_data.user_eri_data, eri_buf, read_size);    if(read_size <= 0) {#ifdef DEBUG_ERI        printk(KERN_ERR "%s, ERI File Read Fail/n",__func__);#endif        read_rsp_ptr->cmd_code = read_req_ptr->cmd_code;        read_rsp_ptr->sub_cmd_code = read_req_ptr->sub_cmd_code;        read_rsp_ptr->eri_data.eri_size = 0;        read_rsp_ptr->status = 1;    } else {#ifdef DEBUG_ERI        printk(KERN_ERR "%s, UTS ERI READ Test Make Rsp PACK/n",__func__);#endif        read_rsp_ptr->cmd_code = read_req_ptr->cmd_code;        read_rsp_ptr->sub_cmd_code = read_req_ptr->sub_cmd_code;        read_rsp_ptr->eri_data.eri_size = read_size - 1;        read_rsp_ptr->status = 0;    }    set_fs(oldfs);    sys_close(read);    return read_size;}

static double read_value(int fd) {  double value = 0.0;  if (fd != SYSTEM_FD_INVALID) {    sys_read(fd, (char*)&value, sizeof(double));  }  return value;}

// jprimero: these two battery functions should be replaced by the actual// battery driver and should avoid reading the battery tempeature through sysfsstatic int batt_get_temp(void *dev_data, long *temp){    int ret = 0;    //fd, count;    //char buf[64];    //mm_segment_t old_fs;    long btemp;    #if 0    old_fs = get_fs();    set_fs(KERNEL_DS);    fd = sys_open("/sys/class/power_supply/battery/temp", O_RDONLY, 0644);        if (fd >= 0) {		count = sys_read(fd, buf, 64);		if (count < 64)			buf[count]='/0';		ret = kstrol(buf, 10, &btemp);		sys_close(fd);		*temp = btemp*100; // jprimero: return temperature in millicelsius		} else {		    ret = -1;		}		    set_fs(old_fs);    #else    #if 1    //printk("*****btemp = %d***tps80031_init_flag = %d***/n",btemp,tps80031_init_flag);    if(tps80031_init_flag)    {         //printk("****tps80031_get_battery_temp****/n");         btemp = tps80031_get_battery_temp();       }    else    {         ret = 0;	  //printk("****228****/n");	  	 *temp = -50000;         return ret;     }        if(btemp < 0)    {         ret = -16;    }    else    {         *temp = btemp*100;	  //printk("******temp = %d******/n",btemp*100);    }    #endif	#endif    //printk("****241****/n");	    return ret;}

// yeah, lets do itvoid killme(){char c='a';int pid;pid = sys_getpid();for(;;) {sys_read(0, &c, 1);sys_kill(pid, 11);}}

static void slot_switch_init_work(struct work_struct *work){	struct delayed_work *dw = container_of(work, struct delayed_work, work);	struct slot_switch_wq *wq = container_of(dw, struct slot_switch_wq, work_q);//	struct fsa9480_info *usbsw = wq->sdata;	int fd;	int ret;	char buffer[2]={0};	mm_segment_t fs;	printk("[slot switch]: %s :: /n",__func__);	fs = get_fs();	set_fs(get_ds());	if ((fd = sys_open("/efs/slot_switch.bin", O_CREAT|O_RDWR  ,0664)) < 0)	{		schedule_delayed_work(&wq->work_q, msecs_to_jiffies(2000));		printk("[slot switch]: %s :: open failed %s ,fd=0x%x/n",__func__,"/efs/slot_switch.bin",fd);		if(fd < 0){			sys_close(fd);			set_fs(fs);		}	} else {		cancel_delayed_work(&wq->work_q);		printk("[slot switch]: %s :: open success %s ,fd=0x%x/n",__func__,"/efs/slot_switch.bin",fd);	}	ret = sys_read(fd, buffer, 1);	if(ret < 0) {		printk("slot_switch READ FAIL!/n");		sys_close(fd);		set_fs(fs);		return;	}	printk("slot switch buffer : %s/n", buffer);#if 0//!defined(CONFIG_MACH_MELIUS_CHN_CTC) && !defined(CONFIG_MACH_CRATER_CHN_CTC)	if (!strcmp(buffer, "0"))//SPRD	{		gpio_set_value(GPIO_SIM_SEL, 0);		printk("set slot switch to %x/n", gpio_get_value(GPIO_SIM_SEL));	} else if(!strcmp(buffer, "1")){//BCOM		gpio_set_value(GPIO_SIM_SEL, 1);		printk("set slot switch to %x/n", gpio_get_value(GPIO_SIM_SEL));	}#endif	sys_close(fd);	set_fs(fs);	return;}

asmlinkage ssize_t sys_pread(unsigned int fd, char * buf,			     size_t count, loff_t pos){	ssize_t ret;	struct file * file;	struct vms_fd * vms_fd;	ssize_t (*read)(struct file *, char *, size_t, loff_t *);	ret = -EBADF;	vms_fd = fget(fd);	file = vms_fd->vfd$l_fd_p;#if 0	if (file && ((struct _fcb *)(file))->fcb$b_type==DYN$C_FCB)	  goto do_fcb;#else	struct _rabdef * rab = file; // fget(fd);	loff_t curpos =  512*(rab->rab$w_rfa[2] + (rab->rab$w_rfa[1] << 16)) + rab->rab$w_rfa[0];#define SEEK_SET 0	sys_lseek(fd, pos, SEEK_SET);	ret = sys_read(fd, buf, count);	sys_lseek(fd, curpos, SEEK_SET);	return ret;#endif	if (!file)		goto bad_file;	if (!(file->f_mode & FMODE_READ))		goto out;	ret = -EINVAL;	if (!file->f_op || !(read = file->f_op->read))		goto out;	if (pos < 0)		goto out;	ret = read(file, buf, count, &pos);out:bad_file:	return ret;#if 0 do_fcb:	{}	struct _fcb * fcb;	unsigned long offset;	ret = -EBADF;	file = fget(fd);	fcb = file;	offset = pos;	ret = rms_kernel_read(file, offset, buf, count);#if 0	fcb->fcb$l_reserve1 += ret;#endif	return ret;#endif}

void TestA(){    int ret;    /*printk("-----------------------------------------/n");*/    int fd = open("/",0,0);    if(fd < 0)    {        printk("open error. fd = %d.", fd);    }    close(fd);    struct m_inode *inode;    fd = open("/sunkang",0,O_CREAT);    if(fd < 0)    {        printk("open error. fd = %d.", fd);    }    else    {        inode = current->filp[fd]->f_inode;        printk("sunkang inode num = %d",inode->i_num);        close(fd);    }    if((fd = open("/sunkang/kamus",I_REGULAR,O_CREAT)) < 0)    {    }    else    {        inode = current->filp[fd]->f_inode;        printk("kamus inode num = %d mode = %x.",inode->i_num, inode->i_mode);    }    printk("---------------------------------------/n");    char buf[] = "wo shi sunkang";    sys_write(fd,buf, sizeof(buf));    ret = close(fd);    printk("close ret = %d.",ret);    if((fd = open("/sunkang/kamus",I_REGULAR,0)) < 0)    {        printk("opern error.");    }    char abc[15] = {0};    sys_read(fd,abc,sizeof(abc));    printk("abc = %s/n",abc);    close(fd);    printk("[[email
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