drivers/usb/mon/mon_stat.c

   1 /*
   2  * The USB Monitor, inspired by Dave Harding's USBMon.
   3  *
   4  * This is the 's' or 'stat' reader which debugs usbmon itself.
   5  * Note that this code blows through locks, so make sure that
   6  * /dbg/usbmon/0s is well protected from non-root users.
   7  *
   8  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/usb.h>
  12 #include <linux/fs.h>
  13 #include <asm/uaccess.h>
  14
  15 #include "usb_mon.h"
  16
  17 #define STAT_BUF_SIZE  80
  18
  19 struct snap {
  20         int slen;
  21         char str[STAT_BUF_SIZE];
  22 };
  23
  24 static int mon_stat_open(struct inode *inode, struct file *file)
  25 {
  26         struct mon_bus *mbus;
  27         struct snap *sp;
  28
  29         if ((sp = kmalloc(sizeof(struct snap), GFP_KERNEL)) == NULL)
  30                 return -ENOMEM;
  31
  32         mbus = inode->i_private;
  33
  34         sp->slen = snprintf(sp->str, STAT_BUF_SIZE,
  35             "nreaders %d events %u text_lost %u\n",
  36             mbus->nreaders, mbus->cnt_events, mbus->cnt_text_lost);
  37
  38         file->private_data = sp;
  39         return 0;
  40 }
  41
  42 static ssize_t mon_stat_read(struct file *file, char __user *buf,
  43                                 size_t nbytes, loff_t *ppos)
  44 {
  45         struct snap *sp = file->private_data;
  46
  47         return simple_read_from_buffer(buf, nbytes, ppos, sp->str, sp->slen);
  48 }
  49
  50 static int mon_stat_release(struct inode *inode, struct file *file)
  51 {
  52         struct snap *sp = file->private_data;
  53         file->private_data = NULL;
  54         kfree(sp);
  55         return 0;
  56 }
  57
  58 const struct file_operations mon_fops_stat = {
  59         .owner =        THIS_MODULE,
  60         .open =         mon_stat_open,
  61         .llseek =       no_llseek,
  62         .read =         mon_stat_read,
  63         /* .write =     mon_stat_write, */
  64         /* .poll =              mon_stat_poll, */
  65         /* .ioctl =     mon_stat_ioctl, */
  66         .release =      mon_stat_release,
  67 };