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