// SPDX-License-Identifier: GPL-2.0
/*
 * The USB Monitor, inspired by Dave Harding's USBMon.
 *
 * This is the 's' or 'stat' reader which debugs usbmon itself.
 * Note that this code blows through locks, so make sure that
 * /dbg/usbmon/0s is well protected from non-root users.
 *
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/export.h>
#include <linux/usb.h>
#include <linux/fs.h>
#include <linux/uaccess.h>

#include "usb_mon.h"

#define STAT_BUF_SIZE  80

struct snap {
        int slen;
        char str[STAT_BUF_SIZE];
};

static int mon_stat_open(struct inode *inode, struct file *file)
{
        struct mon_bus *mbus;
        struct snap *sp;

        sp = kmalloc_obj(struct snap);
        if (sp == NULL)
                return -ENOMEM;

        mbus = inode->i_private;

        sp->slen = scnprintf(sp->str, STAT_BUF_SIZE,
                             "nreaders %d events %u text_lost %u\n",
                             mbus->nreaders, mbus->cnt_events, mbus->cnt_text_lost);

        file->private_data = sp;
        return 0;
}

static ssize_t mon_stat_read(struct file *file, char __user *buf,
                                size_t nbytes, loff_t *ppos)
{
        struct snap *sp = file->private_data;

        return simple_read_from_buffer(buf, nbytes, ppos, sp->str, sp->slen);
}

static int mon_stat_release(struct inode *inode, struct file *file)
{
        struct snap *sp = file->private_data;
        file->private_data = NULL;
        kfree(sp);
        return 0;
}

const struct file_operations mon_fops_stat = {
        .owner =        THIS_MODULE,
        .open =         mon_stat_open,
        .read =         mon_stat_read,
        /* .write =     mon_stat_write, */
        /* .poll =              mon_stat_poll, */
        /* .unlocked_ioctl =    mon_stat_ioctl, */
        .release =      mon_stat_release,
};