/*
 * Copyright (c) 2019-2020 François Tigeot <ftigeot@wolfpond.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice unmodified, this list of conditions, and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/dma-buf.h>
#include <linux/dma-fence.h>
#include <linux/export.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/poll.h>
#include <linux/reservation.h>
#include <linux/mm.h>

struct fileops dmabuf_fileops;

static int
dmabuf_stat(struct file *fp, struct stat *sb, struct ucred *cred)
{
STUB();
        KASSERT(fp->f_type == DTYPE_DMABUF, ("fp is not DMABUF"));
        struct dma_buf *dmabuf = fp->private_data;

        memset(sb, 0, sizeof(*sb));
        sb->st_size = dmabuf->size;
        sb->st_mode = S_IFIFO;  /* XXX */

        return (0);
}

static int
dmabuf_close(struct file *fp)
{
        struct dma_buf *dmabuf;
        if (fp->f_ops != &dmabuf_fileops) {
                kprintf("dmabuf_close(): file->f_ops != &dmabuf_fileops\n");
                return EINVAL;
        }
        dmabuf = fp->private_data;
        dmabuf->ops->release(dmabuf);
        kfree(dmabuf);

        //kprintf("dmabuf_close(): success\n");
        return 0;
}

static int
dmabuf_ioctl(struct file *fp, u_long com, caddr_t data,
            struct ucred *cred, struct sysmsg *msgv)
{
        kprintf("dmabuf_ioctl: com=%lu\n", com);
        return (EBADF);
}

static int
dmabuf_seek(struct file *fp, off_t offset, int whence, off_t *res)
{
        KASSERT(fp->f_type == DTYPE_DMABUF, ("fp is not DMABUF"));
        struct dma_buf *dmabuf = fp->private_data;
        off_t newoff;

        if (offset != 0) {
                return EINVAL;
        }

        switch (whence) {
        case SEEK_SET:
                newoff = 0;
                break;
        case SEEK_END:
                newoff = dmabuf->size;
                break;
        default:
                return EINVAL;
        }
        spin_lock(&fp->f_spin);
        fp->f_offset = newoff;
        spin_unlock(&fp->f_spin);
        *res = newoff;
        return 0;
        
}

struct fileops dmabuf_fileops = {
        .fo_read        = badfo_readwrite,
        .fo_write       = badfo_readwrite,
        .fo_ioctl       = dmabuf_ioctl,
        .fo_kqfilter    = badfo_kqfilter,
        .fo_stat        = dmabuf_stat,
        .fo_close       = dmabuf_close,
        .fo_seek        = dmabuf_seek,
};

struct dma_buf *
dma_buf_export(const struct dma_buf_export_info *exp_info)
{
        struct dma_buf *dmabuf;
        struct file *fp;

        falloc(curthread->td_lwp, &fp, NULL);
        if (fp == NULL)
                return ERR_PTR(-ENFILE);

        dmabuf = kmalloc(sizeof(struct dma_buf), M_DRM, M_WAITOK);
        fp->f_type = DTYPE_DMABUF;
        fp->f_ops = &dmabuf_fileops;
        fp->private_data = dmabuf;
        dmabuf->priv = exp_info->priv;
        dmabuf->ops = exp_info->ops;
        dmabuf->size = exp_info->size;
        dmabuf->file = fp;

        return dmabuf;
}

int
dma_buf_fd(struct dma_buf *dmabuf, int flags)
{
        int fd, error;

        if (dmabuf == NULL)
                return -EINVAL;

        if (dmabuf->file == NULL)
                return -EINVAL;

        if (flags & O_CLOEXEC) {
        /* XXX: CLOEXEC not handled yet */
#if 0
                __set_close_on_exec(fd, fdt);
        else
                __clear_close_on_exec(fd, fdt);
#endif
        }

        error = fdalloc(curproc, 0, &fd);
        if (error != 0)
                return -error;

        fsetfd(curproc->p_fd, dmabuf->file, fd);

        return fd;
}

struct dma_buf *
dma_buf_get(int fd)
{
        struct file *fp;
        struct dma_buf *dmabuf;

        if ((fp = holdfp(curthread, fd, -1)) == NULL)
                return ERR_PTR(-EBADF);

        if (fp->f_ops != &dmabuf_fileops) {
                kprintf("dma_buf_get(): file->f_ops != &dmabuf_fileops\n");
                dropfp(curthread, fd, fp);
                return ERR_PTR(-EBADF);
        }

        dmabuf = fp->private_data;
        dropfp(curthread, fd, fp);

        return dmabuf;
}

struct sg_table *
dma_buf_map_attachment(struct dma_buf_attachment *attach,
                                enum dma_data_direction direction)
{
STUB();
        struct sg_table *sg_table;

        if (attach == NULL)
                return ERR_PTR(-EINVAL);

        if (attach->dmabuf == NULL)
                return ERR_PTR(-EINVAL);

        sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
        if (sg_table == NULL)
                return ERR_PTR(-ENOMEM);

        return sg_table;
}

void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
                                struct sg_table *sg_table,
                                enum dma_data_direction direction)
{
STUB();
}