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 <asm/uaccess.h>
  13
  14 #include "usb_mon.h"
  15
  16 #define STAT_BUF_SIZE  80
  17
  18 struct snap {
  19         int slen;
  20         char str[STAT_BUF_SIZE];
  21 };
  22
  23 static int mon_stat_open(struct inode *inode, struct file *file)
  24 {
  25         struct mon_bus *mbus;
  26         struct snap *sp;
  27
  28         if ((sp = kmalloc(sizeof(struct snap), GFP_KERNEL)) == NULL)
  29                 return -ENOMEM;
  30
  31         mbus = inode->i_private;
  32
  33         sp->slen = snprintf(sp->str, STAT_BUF_SIZE,
  34             "nreaders %d events %u text_lost %u\n",
  35             mbus->nreaders, mbus->cnt_events, mbus->cnt_text_lost);
  36
  37         file->private_data = sp;
  38         return 0;
  39 }
  40
  41 static ssize_t mon_stat_read(struct file *file, char __user *buf,
  42                                 size_t nbytes, loff_t *ppos)
  43 {
  44         struct snap *sp = file->private_data;
  45         loff_t pos = *ppos;
  46         int cnt;
  47
  48         if (pos < 0 || pos >= sp->slen)
  49                 return 0;
  50         if (nbytes == 0)
  51                 return 0;
  52         if ((cnt = sp->slen - pos) > nbytes)
  53                 cnt = nbytes;
  54         if (copy_to_user(buf, sp->str + pos, cnt))
  55                 return -EFAULT;
  56         *ppos = pos + cnt;
  57         return cnt;
  58 }
  59
  60 static int mon_stat_release(struct inode *inode, struct file *file)
  61 {
  62         return 0;
  63 }
  64
  65 const struct file_operations mon_fops_stat = {
  66         .owner =        THIS_MODULE,
  67         .open =         mon_stat_open,
  68         .llseek =       no_llseek,
  69         .read =         mon_stat_read,
  70         /* .write =     mon_stat_write, */
  71         /* .poll =              mon_stat_poll, */
  72         /* .ioctl =     mon_stat_ioctl, */
  73         .release =      mon_stat_release,
  74 };