/*
 *
 * Copyright 1999 Digi International (www.digi.com)
 *     James Puzzo <jamesp at digi dot com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY, EXPRESS OR IMPLIED; without even the
 * implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE.  See the GNU General Public License for more details.
 *
 */

/*
 *
 *  Filename:
 *
 *     dgrp_dpa_ops.c
 *
 *  Description:
 *
 *     Handle the file operations required for the "dpa" devices.
 *     Includes those functions required to register the "dpa" devices
 *     in "/proc".
 *
 *  Author:
 *
 *     James A. Puzzo
 *
 */

#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/tty.h>
#include <linux/poll.h>
#include <linux/cred.h>
#include <linux/sched.h>
#include <linux/ratelimit.h>
#include <linux/slab.h>
#include <asm/unaligned.h>

#include "dgrp_common.h"

/* File operation declarations */
static int dgrp_dpa_open(struct inode *, struct file *);
static int dgrp_dpa_release(struct inode *, struct file *);
static ssize_t dgrp_dpa_read(struct file *, char __user *, size_t, loff_t *);
static long dgrp_dpa_ioctl(struct file *file, unsigned int cmd,
                           unsigned long arg);
static unsigned int dgrp_dpa_select(struct file *, struct poll_table_struct *);

const struct file_operations dgrp_dpa_ops = {
        .owner   =  THIS_MODULE,
        .read    =  dgrp_dpa_read,
        .poll    =  dgrp_dpa_select,
        .unlocked_ioctl =  dgrp_dpa_ioctl,
        .open    =  dgrp_dpa_open,
        .release =  dgrp_dpa_release,
};

struct digi_node {
        uint    nd_state;               /* Node state: 1 = up, 0 = down. */
        uint    nd_chan_count;          /* Number of channels found */
        uint    nd_tx_byte;             /* Tx data count */
        uint    nd_rx_byte;             /* RX data count */
        u8      nd_ps_desc[MAX_DESC_LEN]; /* Description from PS */
};

#define DIGI_GETNODE      (('d'<<8) | 249)      /* get board info */


struct digi_chan {
        uint    ch_port;        /* Port number to get info on */
        uint    ch_open;        /* 1 if open, 0 if not */
        uint    ch_txcount;     /* TX data count  */
        uint    ch_rxcount;     /* RX data count  */
        uint    ch_s_brate;     /* Realport BRATE */
        uint    ch_s_estat;     /* Realport ELAST */
        uint    ch_s_cflag;     /* Realport CFLAG */
        uint    ch_s_iflag;     /* Realport IFLAG */
        uint    ch_s_oflag;     /* Realport OFLAG */
        uint    ch_s_xflag;     /* Realport XFLAG */
        uint    ch_s_mstat;     /* Realport MLAST */
};

#define DIGI_GETCHAN      (('d'<<8) | 248)      /* get channel info */


struct digi_vpd {
        int vpd_len;
        char vpd_data[VPDSIZE];
};

#define DIGI_GETVPD       (('d'<<8) | 246)      /* get VPD info */


struct digi_debug {
        int onoff;
        int port;
};

#define DIGI_SETDEBUG      (('d'<<8) | 247)     /* set debug info */


/*
 * dgrp_dpa_open -- open the DPA device for a particular PortServer
 */
static int dgrp_dpa_open(struct inode *inode, struct file *file)
{
        struct nd_struct *nd;
        int rtn = 0;

        rtn = try_module_get(THIS_MODULE);
        if (!rtn)
                return -ENXIO;

        rtn = 0;

        if (!capable(CAP_SYS_ADMIN)) {
                rtn = -EPERM;
                goto done;
        }

        /*
         *  Make sure that the "private_data" field hasn't already been used.
         */
        if (file->private_data) {
                rtn = -EINVAL;
                goto done;
        }

        /*
         *  Get the node pointer, and fail if it doesn't exist.
         */
        nd = PDE_DATA(inode);
        if (!nd) {
                rtn = -ENXIO;
                goto done;
        }

        file->private_data = (void *) nd;

        /*
         * Allocate the DPA buffer.
         */

        if (nd->nd_dpa_buf) {
                rtn = -EBUSY;
        } else {
                nd->nd_dpa_buf = kmalloc(DPA_MAX, GFP_KERNEL);

                if (!nd->nd_dpa_buf) {
                        rtn = -ENOMEM;
                } else {
                        nd->nd_dpa_out = 0;
                        nd->nd_dpa_in = 0;
                        nd->nd_dpa_lbolt = jiffies;
                }
        }

done:

        if (rtn)
                module_put(THIS_MODULE);
        return rtn;
}

/*
 * dgrp_dpa_release -- close the DPA device for a particular PortServer
 */
static int dgrp_dpa_release(struct inode *inode, struct file *file)
{
        struct nd_struct *nd;
        u8 *buf;
        unsigned long lock_flags;

        /*
         *  Get the node pointer, and quit if it doesn't exist.
         */
        nd = (struct nd_struct *)(file->private_data);
        if (!nd)
                goto done;

        /*
         *  Free the dpa buffer.
         */

        spin_lock_irqsave(&nd->nd_dpa_lock, lock_flags);

        buf = nd->nd_dpa_buf;

        nd->nd_dpa_buf = NULL;
        nd->nd_dpa_out = nd->nd_dpa_in;

        /*
         *  Wakeup any thread waiting for buffer space.
         */

        if (nd->nd_dpa_flag & DPA_WAIT_SPACE) {
                nd->nd_dpa_flag &= ~DPA_WAIT_SPACE;
                wake_up_interruptible(&nd->nd_dpa_wqueue);
        }

        spin_unlock_irqrestore(&nd->nd_dpa_lock, lock_flags);

        kfree(buf);

done:
        module_put(THIS_MODULE);
        file->private_data = NULL;
        return 0;
}

/*
 * dgrp_dpa_read
 *
 * Copy data from the monitoring buffer to the user, freeing space
 * in the monitoring buffer for more messages
 */
static ssize_t dgrp_dpa_read(struct file *file, char __user *buf, size_t count,
                             loff_t *ppos)
{
        struct nd_struct *nd;
        int n;
        int r;
        int offset = 0;
        int res = 0;
        ssize_t rtn;
        unsigned long lock_flags;

        /*
         *  Get the node pointer, and quit if it doesn't exist.
         */
        nd = (struct nd_struct *)(file->private_data);
        if (!nd)
                return -ENXIO;

        /*
         *  Wait for some data to appear in the buffer.
         */

        spin_lock_irqsave(&nd->nd_dpa_lock, lock_flags);

        for (;;) {
                n = (nd->nd_dpa_in - nd->nd_dpa_out) & DPA_MASK;

                if (n != 0)
                        break;

                nd->nd_dpa_flag |= DPA_WAIT_DATA;

                spin_unlock_irqrestore(&nd->nd_dpa_lock, lock_flags);

                /*
                 * Go to sleep waiting until the condition becomes true.
                 */
                rtn = wait_event_interruptible(nd->nd_dpa_wqueue,
                        ((nd->nd_dpa_flag & DPA_WAIT_DATA) == 0));

                if (rtn)
                        return rtn;

                spin_lock_irqsave(&nd->nd_dpa_lock, lock_flags);
        }

        /*
         *  Read whatever is there.
         */

        if (n > count)
                n = count;

        res = n;

        r = DPA_MAX - nd->nd_dpa_out;

        if (r <= n) {

                spin_unlock_irqrestore(&nd->nd_dpa_lock, lock_flags);
                rtn = copy_to_user((void __user *)buf,
                                   nd->nd_dpa_buf + nd->nd_dpa_out, r);
                spin_lock_irqsave(&nd->nd_dpa_lock, lock_flags);

                if (rtn) {
                        rtn = -EFAULT;
                        goto done;
                }

                nd->nd_dpa_out = 0;
                n -= r;
                offset = r;
        }

        spin_unlock_irqrestore(&nd->nd_dpa_lock, lock_flags);
        rtn = copy_to_user((void __user *)buf + offset,
                           nd->nd_dpa_buf + nd->nd_dpa_out, n);
        spin_lock_irqsave(&nd->nd_dpa_lock, lock_flags);

        if (rtn) {
                rtn = -EFAULT;
                goto done;
        }

        nd->nd_dpa_out += n;

        *ppos += res;

        rtn = res;

        /*
         *  Wakeup any thread waiting for buffer space.
         */

        n = (nd->nd_dpa_in - nd->nd_dpa_out) & DPA_MASK;

        if (nd->nd_dpa_flag & DPA_WAIT_SPACE &&
            (DPA_MAX - n) > DPA_HIGH_WATER) {
                nd->nd_dpa_flag &= ~DPA_WAIT_SPACE;
                wake_up_interruptible(&nd->nd_dpa_wqueue);
        }

 done:
        spin_unlock_irqrestore(&nd->nd_dpa_lock, lock_flags);
        return rtn;
}

static unsigned int dgrp_dpa_select(struct file *file,
                                    struct poll_table_struct *table)
{
        unsigned int retval = 0;
        struct nd_struct *nd = file->private_data;

        if (nd->nd_dpa_out != nd->nd_dpa_in)
                retval |= POLLIN | POLLRDNORM; /* Conditionally readable */

        retval |= POLLOUT | POLLWRNORM;        /* Always writeable */

        return retval;
}

static long dgrp_dpa_ioctl(struct file *file, unsigned int cmd,
                           unsigned long arg)
{

        struct nd_struct  *nd;
        struct digi_chan getchan;
        struct digi_node getnode;
        struct ch_struct *ch;
        struct digi_debug setdebug;
        struct digi_vpd vpd;
        unsigned int port;
        void __user *uarg = (void __user *) arg;

        nd = file->private_data;

        switch (cmd) {
        case DIGI_GETCHAN:
                if (copy_from_user(&getchan, uarg, sizeof(struct digi_chan)))
                        return -EFAULT;

                port = getchan.ch_port;

                if (port > nd->nd_chan_count)
                        return -EINVAL;

                ch = nd->nd_chan + port;

                getchan.ch_open = (ch->ch_open_count > 0) ? 1 : 0;
                getchan.ch_txcount = ch->ch_txcount;
                getchan.ch_rxcount = ch->ch_rxcount;
                getchan.ch_s_brate = ch->ch_s_brate;
                getchan.ch_s_estat = ch->ch_s_elast;
                getchan.ch_s_cflag = ch->ch_s_cflag;
                getchan.ch_s_iflag = ch->ch_s_iflag;
                getchan.ch_s_oflag = ch->ch_s_oflag;
                getchan.ch_s_xflag = ch->ch_s_xflag;
                getchan.ch_s_mstat = ch->ch_s_mlast;

                if (copy_to_user(uarg, &getchan, sizeof(struct digi_chan)))
                        return -EFAULT;
                break;


        case DIGI_GETNODE:
                getnode.nd_state = (nd->nd_state & NS_READY) ? 1 : 0;
                getnode.nd_chan_count = nd->nd_chan_count;
                getnode.nd_tx_byte = nd->nd_tx_byte;
                getnode.nd_rx_byte = nd->nd_rx_byte;

                memset(&getnode.nd_ps_desc, 0, MAX_DESC_LEN);
                strlcpy(getnode.nd_ps_desc, nd->nd_ps_desc, MAX_DESC_LEN);

                if (copy_to_user(uarg, &getnode, sizeof(struct digi_node)))
                        return -EFAULT;
                break;


        case DIGI_SETDEBUG:
                if (copy_from_user(&setdebug, uarg, sizeof(struct digi_debug)))
                        return -EFAULT;

                nd->nd_dpa_debug = setdebug.onoff;
                nd->nd_dpa_port = setdebug.port;
                break;


        case DIGI_GETVPD:
                memset(&vpd, 0, sizeof(vpd));
                if (nd->nd_vpd_len > 0) {
                        vpd.vpd_len = nd->nd_vpd_len;
                        memcpy(&vpd.vpd_data, &nd->nd_vpd, nd->nd_vpd_len);
                } else {
                        vpd.vpd_len = 0;
                }

                if (copy_to_user(uarg, &vpd, sizeof(struct digi_vpd)))
                        return -EFAULT;
                break;
        }

        return 0;
}

/**
 * dgrp_dpa() -- send data to the device monitor queue
 * @nd: pointer to a node structure
 * @buf: buffer of data to copy to the monitoring buffer
 * @len: number of bytes to transfer to the buffer
 *
 * Called by the net device routines to send data to the device
 * monitor queue.  If the device monitor buffer is too full to
 * accept the data, it waits until the buffer is ready.
 */
static void dgrp_dpa(struct nd_struct *nd, u8 *buf, int nbuf)
{
        int n;
        int r;
        unsigned long lock_flags;

        /*
         *  Grab DPA lock.
         */
        spin_lock_irqsave(&nd->nd_dpa_lock, lock_flags);

        /*
         *  Loop while data remains.
         */
        while (nbuf > 0 && nd->nd_dpa_buf != NULL) {

                n = (nd->nd_dpa_out - nd->nd_dpa_in - 1) & DPA_MASK;

                /*
                 * Enforce flow control on the DPA device.
                 */
                if (n < (DPA_MAX - DPA_HIGH_WATER))
                        nd->nd_dpa_flag |= DPA_WAIT_SPACE;

                /*
                 * This should never happen, as the flow control above
                 * should have stopped things before they got to this point.
                 */
                if (n == 0) {
                        spin_unlock_irqrestore(&nd->nd_dpa_lock, lock_flags);
                        return;
                }

                /*
                 * Copy as much data as will fit.
                 */

                if (n > nbuf)
                        n = nbuf;

                r = DPA_MAX - nd->nd_dpa_in;

                if (r <= n) {
                        memcpy(nd->nd_dpa_buf + nd->nd_dpa_in, buf, r);

                        n -= r;

                        nd->nd_dpa_in = 0;

                        buf += r;
                        nbuf -= r;
                }

                memcpy(nd->nd_dpa_buf + nd->nd_dpa_in, buf, n);

                nd->nd_dpa_in += n;

                buf += n;
                nbuf -= n;

                if (nd->nd_dpa_in >= DPA_MAX)
                        pr_info_ratelimited("%s - nd->nd_dpa_in (%i) >= DPA_MAX\n",
                                            __func__, nd->nd_dpa_in);

                /*
                 *  Wakeup any thread waiting for data
                 */
                if (nd->nd_dpa_flag & DPA_WAIT_DATA) {
                        nd->nd_dpa_flag &= ~DPA_WAIT_DATA;
                        wake_up_interruptible(&nd->nd_dpa_wqueue);
                }
        }

        /*
         *  Release the DPA lock.
         */
        spin_unlock_irqrestore(&nd->nd_dpa_lock, lock_flags);
}

/**
 * dgrp_monitor_data() -- builds a DPA data packet
 * @nd: pointer to a node structure
 * @type: type of message to be logged in the DPA buffer
 * @buf: buffer of data to be logged in the DPA buffer
 * @size -- number of bytes in the "buf" buffer
 */
void dgrp_dpa_data(struct nd_struct *nd, int type, u8 *buf, int size)
{
        u8 header[5];

        header[0] = type;

        put_unaligned_be32(size, header + 1);

        dgrp_dpa(nd, header, sizeof(header));
        dgrp_dpa(nd, buf, size);
}