学步园

drivers/mtd/nandsim.c

<1>:打开文件

  cfile = filp_open(cache_file, O_CREAT | O_RDWR | O_LARGEFILE, 0600);
  if (IS_ERR(cfile))
   return PTR_ERR(cfile);
  if (!cfile->f_op || (!cfile->f_op->read && !cfile->f_op->aio_read)) {
   NS_ERR("alloc_device: cache file not readable/n");
   err = -EINVAL;
   goto err_close;
  }
  if (!cfile->f_op->write && !cfile->f_op->aio_write) {
   NS_ERR("alloc_device: cache file not writeable/n");
   err = -EINVAL;
   goto err_close;
  }

<2>:读文件

static ssize_t read_file(struct nandsim *ns, struct file *file, void *buf, size_t count, loff_t *pos)
{
 mm_segment_t old_fs;
 ssize_t tx;
 int err, memalloc;

 err = get_pages(ns, file, count, *pos);
 if (err)
  return err;
 old_fs = get_fs();
 set_fs(get_ds());    //将地址空间设置为内核空间，防止vfs_read返回失败
 memalloc = set_memalloc();
 tx = vfs_read(file, (char __user *)buf, count, pos);
 clear_memalloc(memalloc);
 set_fs(old_fs);
 put_pages(ns);
 return tx;
}

<3>:写文件

static ssize_t write_file(struct nandsim *ns, struct file *file, void *buf, size_t count, loff_t *pos)
{
 mm_segment_t old_fs;
 ssize_t tx;
 int err, memalloc;

 err = get_pages(ns, file, count, *pos);
 if (err)
  return err;
 old_fs = get_fs();
 set_fs(get_ds());  //#define get_ds() (KERNEL_DS)
 memalloc = set_memalloc();
 tx = vfs_write(file, (char __user *)buf, count, pos);
 clear_memalloc(memalloc);
 set_fs(old_fs);
 put_pages(ns);
 return tx;
}

/*<br /> * createfile.c<br /> * Author: Woody <Pecker.hu@gmail.com><br /> *<br /> * Use kernel APIs to create a file<br /> *<br /> * This program is free software; you can redistribute it and/or modify<br /> * it under the terms of the GNU General Public License version 2 as<br /> * published by the Free Software Foundation.<br /> *<br /> */ </p> <p>#include <linux/module.h> /* MODULE_LICENSE */<br /> #include <linux/kernel.h> /* printk,pr_info */<br /> #include <linux/errno.h> /* EINVAL,EAGAIN,etc. */<br /> #include <linux/err.h> /* IS_ERR */<br /> #include <linux/init.h> /* module_init */<br /> #include <linux/delay.h> /* mdelay,msleep */<br /> #include <linux/hrtimer.h> /* hrtimer APIs */<br /> #include <linux/time.h> /* struct timespec */<br /> #include <linux/device.h> /* device_create */<br /> #include <linux/fs.h><br /> #include <linux/slab.h> /* kzalloc */<br /> #include <asm/uaccess.h> /* get_fs */<br /> #include <linux/mutex.h> /* struct mutex */<br /> struct kernel_test { /* Just for kernel test code */<br /> wait_queue_head_t waitq;<br /> struct mutex test_lock;<br /> struct class *sys_print_class;<br /> struct device *dev;<br /> int rw_flag;<br /> int print_flag;<br /> };<br /> static struct kernel_test *data;<br /> static ssize_t enable_show(struct device *dev, struct device_attribute *attr,<br /> char *buf)<br /> {<br /> int ret = 0;<br /> DECLARE_WAITQUEUE(wait, current);<br /> set_current_state(TASK_UNINTERRUPTIBLE);<br /> add_wait_queue(&data->waitq, &wait);<br /> if (data->rw_flag == 0) {<br /> printk("Begin to sched...>/n");<br /> schedule();<br /> } </p> <p> printk("@@@@@@@@@@@@Wake up the current/n");<br /> remove_wait_queue(&data->waitq, &wait);<br /> set_current_state(TASK_RUNNING);<br /> ret = sprintf(buf, "%d/n", data->print_flag);</p> <p> data->rw_flag = 0;<br /> return ret;<br /> } </p> <p>static ssize_t enable_store(<br /> struct device *dev, struct device_attribute *attr,<br /> const char *buf, size_t size)<br /> {<br /> sscanf(buf, "%d", &data->print_flag);</p> <p> data->rw_flag = 1;<br /> wake_up(&data->waitq);<br /> return size;<br /> }<br /> static DEVICE_ATTR(enable, 0644, enable_show, enable_store);<br /> static int open_file(void)<br /> {<br /> struct file * cfile;<br /> uint32_t err = 0;<br /> mm_segment_t old_fs;<br /> ssize_t tx;<br /> uint8_t buf[16] = "Hello World!";<br /> loff_t pos = 0;</p> <p> cfile = filp_open("/kernel_test", O_CREAT | O_RDWR | O_LARGEFILE, 0644);<br /> if (IS_ERR(cfile))<br /> return PTR_ERR(cfile);</p> <p> if (!cfile->f_op || (!cfile->f_op->read && !cfile->f_op->aio_read)) {<br /> printk("alloc_device: cache file not readable/n");<br /> err = -EINVAL;<br /> goto err_close;<br /> }<br /> if (!cfile->f_op->write && !cfile->f_op->aio_write) {<br /> printk("alloc_device: cache file not writeable/n");<br /> err = -EINVAL;<br /> goto err_close;<br /> }<br /> printk("Open the file /huyugui/log/n");<br /> old_fs = get_fs();<br /> set_fs(get_ds());<br /> tx = vfs_write(cfile, (char __user *)buf, 16, &pos);<br /> set_fs(old_fs);</p> <p>err_close:<br /> filp_close(cfile, NULL);<br /> return err;<br /> }<br /> static int __init file_init_module(void)<br /> {<br /> int ret = 0;<br /> printk("[%s,%d]/n", __FUNCTION__, __LINE__);<br /> data = kzalloc(sizeof(struct kernel_test), GFP_KERNEL);<br /> if (data == NULL) {<br /> printk("[%s,%d]out of memory!/n", __FUNCTION__, __LINE__);<br /> return -ENOMEM;<br /> } </p> <p> mutex_init(&data->test_lock);<br /> init_waitqueue_head(&data->waitq);<br /> data->rw_flag = 0; /* when write new data,the rw_flag will be set to "1" */<br /> data->sys_print_class = class_create(THIS_MODULE, "kernel_test");<br /> if (IS_ERR(data->sys_print_class)) {<br /> ret = PTR_ERR(data->sys_print_class);<br /> goto fail;<br /> } else {<br /> printk("Create the /sys/class/kernel_test/n");<br /> }</p> <p> data->dev = device_create(data->sys_print_class,<br /> NULL, MKDEV(255, 0), NULL, "file");<br /> printk("Create the foder:/sys/class/kernel_test/file/n");<br /> ret = device_create_file(data->dev, &dev_attr_enable);<br /> ret = open_file();<br /> if (ret == 0) {<br /> printk("Create file successfully!/n");<br /> } else {<br /> printk("Create file failed!/n");<br /> }<br /> goto out;</p> <p>fail:<br /> kfree(data);<br /> out:<br /> return ret;<br /> } </p> <p>static void __exit file_cleanup_module(void)<br /> {<br /> printk("[%s,%d]/n", __FUNCTION__, __LINE__);</p> <p> device_remove_file(data->dev, &dev_attr_enable);<br /> device_destroy(data->sys_print_class, MKDEV(255, 0));<br /> class_destroy(data->sys_print_class);<br /> kfree(data); /* free the memory when remove modules */</p> <p>}<br /> module_init(file_init_module);<br /> module_exit(file_cleanup_module); </p> <p>MODULE_AUTHOR("Woody <Pecker.hu@gmail.com>");<br /> MODULE_DESCRIPTION("Use Kernel APIs to create files");<br /> MODULE_LICENSE("GPL");<br />