/*
 * STK1160 driver
 *
 * Copyright (C) 2012 Ezequiel Garcia
 * <elezegarcia--a.t--gmail.com>
 *
 * Based on Easycap driver by R.M. Thomas
 *      Copyright (C) 2010 R.M. Thomas
 *      <rmthomas--a.t--sciolus.org>
 *
 * 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 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */

#include <linux/module.h>
#include <linux/usb.h>
#include <linux/slab.h>
#include <linux/ratelimit.h>

#include "stk1160.h"

static unsigned int debug;
module_param(debug, int, 0644);
MODULE_PARM_DESC(debug, "enable debug messages");

static inline void print_err_status(struct stk1160 *dev,
                                     int packet, int status)
{
        char *errmsg = "Unknown";

        switch (status) {
        case -ENOENT:
                errmsg = "unlinked synchronously";
                break;
        case -ECONNRESET:
                errmsg = "unlinked asynchronously";
                break;
        case -ENOSR:
                errmsg = "Buffer error (overrun)";
                break;
        case -EPIPE:
                errmsg = "Stalled (device not responding)";
                break;
        case -EOVERFLOW:
                errmsg = "Babble (bad cable?)";
                break;
        case -EPROTO:
                errmsg = "Bit-stuff error (bad cable?)";
                break;
        case -EILSEQ:
                errmsg = "CRC/Timeout (could be anything)";
                break;
        case -ETIME:
                errmsg = "Device does not respond";
                break;
        }

        if (packet < 0)
                printk_ratelimited(KERN_WARNING "URB status %d [%s].\n",
                                status, errmsg);
        else
                printk_ratelimited(KERN_INFO "URB packet %d, status %d [%s].\n",
                               packet, status, errmsg);
}

static inline
struct stk1160_buffer *stk1160_next_buffer(struct stk1160 *dev)
{
        struct stk1160_buffer *buf = NULL;
        unsigned long flags = 0;

        /* Current buffer must be NULL when this functions gets called */
        WARN_ON(dev->isoc_ctl.buf);

        spin_lock_irqsave(&dev->buf_lock, flags);
        if (!list_empty(&dev->avail_bufs)) {
                buf = list_first_entry(&dev->avail_bufs,
                                struct stk1160_buffer, list);
                list_del(&buf->list);
        }
        spin_unlock_irqrestore(&dev->buf_lock, flags);

        return buf;
}

static inline
void stk1160_buffer_done(struct stk1160 *dev)
{
        struct stk1160_buffer *buf = dev->isoc_ctl.buf;

        buf->vb.sequence = dev->sequence++;
        buf->vb.field = V4L2_FIELD_INTERLACED;
        buf->vb.vb2_buf.timestamp = ktime_get_ns();

        vb2_set_plane_payload(&buf->vb.vb2_buf, 0, buf->bytesused);
        vb2_buffer_done(&buf->vb.vb2_buf, VB2_BUF_STATE_DONE);

        dev->isoc_ctl.buf = NULL;
}

static inline
void stk1160_copy_video(struct stk1160 *dev, u8 *src, int len)
{
        int linesdone, lineoff, lencopy;
        int bytesperline = dev->width * 2;
        struct stk1160_buffer *buf = dev->isoc_ctl.buf;
        u8 *dst = buf->mem;
        int remain;

        /*
         * TODO: These stk1160_dbg are very spammy!
         * We should 1) check why we are getting them
         * and 2) add ratelimit.
         *
         * UPDATE: One of the reasons (the only one?) for getting these
         * is incorrect standard (mismatch between expected and configured).
         * So perhaps, we could add a counter for errors. When the counter
         * reaches some value, we simply stop streaming.
         */

        len -= 4;
        src += 4;

        remain = len;

        linesdone = buf->pos / bytesperline;
        lineoff = buf->pos % bytesperline; /* offset in current line */

        if (!buf->odd)
                dst += bytesperline;

        /* Multiply linesdone by two, to take account of the other field */
        dst += linesdone * bytesperline * 2 + lineoff;

        /* Copy the remaining of current line */
        if (remain < (bytesperline - lineoff))
                lencopy = remain;
        else
                lencopy = bytesperline - lineoff;

        /*
         * Check if we have enough space left in the buffer.
         * In that case, we force loop exit after copy.
         */
        if (lencopy > buf->bytesused - buf->length) {
                lencopy = buf->bytesused - buf->length;
                remain = lencopy;
        }

        /* Check if the copy is done */
        if (lencopy == 0 || remain == 0)
                return;

        /* Let the bug hunt begin! sanity checks! */
        if (lencopy < 0) {
                stk1160_dbg("copy skipped: negative lencopy\n");
                return;
        }

        if ((unsigned long)dst + lencopy >
                (unsigned long)buf->mem + buf->length) {
                printk_ratelimited(KERN_WARNING "stk1160: buffer overflow detected\n");
                return;
        }

        memcpy(dst, src, lencopy);

        buf->bytesused += lencopy;
        buf->pos += lencopy;
        remain -= lencopy;

        /* Copy current field line by line, interlacing with the other field */
        while (remain > 0) {

                dst += lencopy + bytesperline;
                src += lencopy;

                /* Copy one line at a time */
                if (remain < bytesperline)
                        lencopy = remain;
                else
                        lencopy = bytesperline;

                /*
                 * Check if we have enough space left in the buffer.
                 * In that case, we force loop exit after copy.
                 */
                if (lencopy > buf->bytesused - buf->length) {
                        lencopy = buf->bytesused - buf->length;
                        remain = lencopy;
                }

                /* Check if the copy is done */
                if (lencopy == 0 || remain == 0)
                        return;

                if (lencopy < 0) {
                        printk_ratelimited(KERN_WARNING "stk1160: negative lencopy detected\n");
                        return;
                }

                if ((unsigned long)dst + lencopy >
                        (unsigned long)buf->mem + buf->length) {
                        printk_ratelimited(KERN_WARNING "stk1160: buffer overflow detected\n");
                        return;
                }

                memcpy(dst, src, lencopy);
                remain -= lencopy;

                buf->bytesused += lencopy;
                buf->pos += lencopy;
        }
}

/*
 * Controls the isoc copy of each urb packet
 */
static void stk1160_process_isoc(struct stk1160 *dev, struct urb *urb)
{
        int i, len, status;
        u8 *p;

        if (!dev) {
                stk1160_warn("%s called with null device\n", __func__);
                return;
        }

        if (urb->status < 0) {
                /* Print status and drop current packet (or field?) */
                print_err_status(dev, -1, urb->status);
                return;
        }

        for (i = 0; i < urb->number_of_packets; i++) {
                status = urb->iso_frame_desc[i].status;
                if (status < 0) {
                        print_err_status(dev, i, status);
                        continue;
                }

                /* Get packet actual length and pointer to data */
                p = urb->transfer_buffer + urb->iso_frame_desc[i].offset;
                len = urb->iso_frame_desc[i].actual_length;

                /* Empty packet */
                if (len <= 4)
                        continue;

                /*
                 * An 8-byte packet sequence means end of field.
                 * So if we don't have any packet, we start receiving one now
                 * and if we do have a packet, then we are done with it.
                 *
                 * These end of field packets are always 0xc0 or 0x80,
                 * but not always 8-byte long so we don't check packet length.
                 */
                if (p[0] == 0xc0) {

                        /*
                         * If first byte is 0xc0 then we received
                         * second field, and frame has ended.
                         */
                        if (dev->isoc_ctl.buf != NULL)
                                stk1160_buffer_done(dev);

                        dev->isoc_ctl.buf = stk1160_next_buffer(dev);
                        if (dev->isoc_ctl.buf == NULL)
                                return;
                }

                /*
                 * If we don't have a buffer here, then it means we
                 * haven't found the start mark sequence.
                 */
                if (dev->isoc_ctl.buf == NULL)
                        continue;

                if (p[0] == 0xc0 || p[0] == 0x80) {

                        /* We set next packet parity and
                         * continue to get next one
                         */
                        dev->isoc_ctl.buf->odd = *p & 0x40;
                        dev->isoc_ctl.buf->pos = 0;
                        continue;
                }

                stk1160_copy_video(dev, p, len);
        }
}


/*
 * IRQ callback, called by URB callback
 */
static void stk1160_isoc_irq(struct urb *urb)
{
        int i, rc;
        struct stk1160 *dev = urb->context;

        switch (urb->status) {
        case 0:
                break;
        case -ECONNRESET:   /* kill */
        case -ENOENT:
        case -ESHUTDOWN:
                /* TODO: check uvc driver: he frees the queue here */
                return;
        default:
                stk1160_err("urb error! status %d\n", urb->status);
                return;
        }

        stk1160_process_isoc(dev, urb);

        /* Reset urb buffers */
        for (i = 0; i < urb->number_of_packets; i++) {
                urb->iso_frame_desc[i].status = 0;
                urb->iso_frame_desc[i].actual_length = 0;
        }

        rc = usb_submit_urb(urb, GFP_ATOMIC);
        if (rc)
                stk1160_err("urb re-submit failed (%d)\n", rc);
}

/*
 * Cancel urbs
 * This function can't be called in atomic context
 */
void stk1160_cancel_isoc(struct stk1160 *dev)
{
        int i, num_bufs = dev->isoc_ctl.num_bufs;

        /*
         * This check is not necessary, but we add it
         * to avoid a spurious debug message
         */
        if (!num_bufs)
                return;

        stk1160_dbg("killing %d urbs...\n", num_bufs);

        for (i = 0; i < num_bufs; i++) {

                /*
                 * To kill urbs we can't be in atomic context.
                 * We don't care for NULL pointer since
                 * usb_kill_urb allows it.
                 */
                usb_kill_urb(dev->isoc_ctl.urb[i]);
        }

        stk1160_dbg("all urbs killed\n");
}

/*
 * Releases urb and transfer buffers
 * Obviusly, associated urb must be killed before releasing it.
 */
void stk1160_free_isoc(struct stk1160 *dev)
{
        struct urb *urb;
        int i, num_bufs = dev->isoc_ctl.num_bufs;

        stk1160_dbg("freeing %d urb buffers...\n", num_bufs);

        for (i = 0; i < num_bufs; i++) {

                urb = dev->isoc_ctl.urb[i];
                if (urb) {

                        if (dev->isoc_ctl.transfer_buffer[i]) {
#ifndef CONFIG_DMA_NONCOHERENT
                                usb_free_coherent(dev->udev,
                                        urb->transfer_buffer_length,
                                        dev->isoc_ctl.transfer_buffer[i],
                                        urb->transfer_dma);
#else
                                kfree(dev->isoc_ctl.transfer_buffer[i]);
#endif
                        }
                        usb_free_urb(urb);
                        dev->isoc_ctl.urb[i] = NULL;
                }
                dev->isoc_ctl.transfer_buffer[i] = NULL;
        }

        kfree(dev->isoc_ctl.urb);
        kfree(dev->isoc_ctl.transfer_buffer);

        dev->isoc_ctl.urb = NULL;
        dev->isoc_ctl.transfer_buffer = NULL;
        dev->isoc_ctl.num_bufs = 0;

        stk1160_dbg("all urb buffers freed\n");
}

/*
 * Helper for cancelling and freeing urbs
 * This function can't be called in atomic context
 */
void stk1160_uninit_isoc(struct stk1160 *dev)
{
        stk1160_cancel_isoc(dev);
        stk1160_free_isoc(dev);
}

/*
 * Allocate URBs
 */
int stk1160_alloc_isoc(struct stk1160 *dev)
{
        struct urb *urb;
        int i, j, k, sb_size, max_packets, num_bufs;

        /*
         * It may be necessary to release isoc here,
         * since isoc are only released on disconnection.
         * (see new_pkt_size flag)
         */
        if (dev->isoc_ctl.num_bufs)
                stk1160_uninit_isoc(dev);

        stk1160_dbg("allocating urbs...\n");

        num_bufs = STK1160_NUM_BUFS;
        max_packets = STK1160_NUM_PACKETS;
        sb_size = max_packets * dev->max_pkt_size;

        dev->isoc_ctl.buf = NULL;
        dev->isoc_ctl.max_pkt_size = dev->max_pkt_size;
        dev->isoc_ctl.urb = kzalloc(sizeof(void *)*num_bufs, GFP_KERNEL);
        if (!dev->isoc_ctl.urb) {
                stk1160_err("out of memory for urb array\n");
                return -ENOMEM;
        }

        dev->isoc_ctl.transfer_buffer = kzalloc(sizeof(void *)*num_bufs,
                                              GFP_KERNEL);
        if (!dev->isoc_ctl.transfer_buffer) {
                stk1160_err("out of memory for usb transfers\n");
                kfree(dev->isoc_ctl.urb);
                return -ENOMEM;
        }

        /* allocate urbs and transfer buffers */
        for (i = 0; i < num_bufs; i++) {

                urb = usb_alloc_urb(max_packets, GFP_KERNEL);
                if (!urb)
                        goto free_i_bufs;
                dev->isoc_ctl.urb[i] = urb;

#ifndef CONFIG_DMA_NONCOHERENT
                dev->isoc_ctl.transfer_buffer[i] = usb_alloc_coherent(dev->udev,
                        sb_size, GFP_KERNEL, &urb->transfer_dma);
#else
                dev->isoc_ctl.transfer_buffer[i] = kmalloc(sb_size, GFP_KERNEL);
#endif
                if (!dev->isoc_ctl.transfer_buffer[i]) {
                        stk1160_err("cannot alloc %d bytes for tx[%d] buffer\n",
                                sb_size, i);

                        /* Not enough transfer buffers, so just give up */
                        if (i < STK1160_MIN_BUFS)
                                goto free_i_bufs;
                        goto nomore_tx_bufs;
                }
                memset(dev->isoc_ctl.transfer_buffer[i], 0, sb_size);

                /*
                 * FIXME: Where can I get the endpoint?
                 */
                urb->dev = dev->udev;
                urb->pipe = usb_rcvisocpipe(dev->udev, STK1160_EP_VIDEO);
                urb->transfer_buffer = dev->isoc_ctl.transfer_buffer[i];
                urb->transfer_buffer_length = sb_size;
                urb->complete = stk1160_isoc_irq;
                urb->context = dev;
                urb->interval = 1;
                urb->start_frame = 0;
                urb->number_of_packets = max_packets;
#ifndef CONFIG_DMA_NONCOHERENT
                urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
#else
                urb->transfer_flags = URB_ISO_ASAP;
#endif

                k = 0;
                for (j = 0; j < max_packets; j++) {
                        urb->iso_frame_desc[j].offset = k;
                        urb->iso_frame_desc[j].length =
                                        dev->isoc_ctl.max_pkt_size;
                        k += dev->isoc_ctl.max_pkt_size;
                }
        }

        stk1160_dbg("%d urbs allocated\n", num_bufs);

        /* At last we can say we have some buffers */
        dev->isoc_ctl.num_bufs = num_bufs;

        return 0;

nomore_tx_bufs:
        /*
         * Failed to allocate desired buffer count. However, we may have
         * enough to work fine, so we just free the extra urb,
         * store the allocated count and keep going, fingers crossed!
         */
        usb_free_urb(dev->isoc_ctl.urb[i]);
        dev->isoc_ctl.urb[i] = NULL;

        stk1160_warn("%d urbs allocated. Trying to continue...\n", i - 1);

        dev->isoc_ctl.num_bufs = i - 1;

        return 0;

free_i_bufs:
        /* Save the allocated buffers so far, so we can properly free them */
        dev->isoc_ctl.num_bufs = i+1;
        stk1160_free_isoc(dev);
        return -ENOMEM;
}