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