/*
 * Copyright (C) 2007 Jens Axboe <jens.axboe@oracle.com>
 *
 * Scatterlist handling helpers.
 *
 * This source code is licensed under the GNU General Public License,
 * Version 2. See the file COPYING for more details.
 */

#include <linux/scatterlist.h>
#include <linux/slab.h>

#include "vmwgfx_compat.h"
#if (LINUX_VERSION_CODE < KERNEL_VERSION(3, 6, 0))

/**
 * sg_alloc_table_from_pages - Allocate and initialize an sg table from
 *			       an array of pages
 * @sgt:	The sg table header to use
 * @pages:	Pointer to an array of page pointers
 * @n_pages:	Number of pages in the pages array
 * @offset:     Offset from start of the first page to the start of a buffer
 * @size:       Number of valid bytes in the buffer (after offset)
 * @gfp_mask:	GFP allocation mask
 *
 *  Description:
 *    Allocate and initialize an sg table from a list of pages. Contiguous
 *    ranges of the pages are squashed into a single scatterlist node. A user
 *    may provide an offset at a start and a size of valid data in a buffer
 *    specified by the page array. The returned sg table is released by
 *    sg_free_table.
 *
 * Returns:
 *   0 on success, negative error on failure
 */
int sg_alloc_table_from_pages(struct sg_table *sgt,
	struct page **pages, unsigned int n_pages,
	unsigned long offset, unsigned long size,
	gfp_t gfp_mask)
{
	unsigned int chunks;
	unsigned int i;
	unsigned int cur_page;
	int ret;
	struct scatterlist *s;

	/* compute number of contiguous chunks */
	chunks = 1;
	for (i = 1; i < n_pages; ++i)
		if (page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) + 1)
			++chunks;

	ret = sg_alloc_table(sgt, chunks, gfp_mask);
	if (unlikely(ret))
		return ret;

	/* merging chunks and putting them into the scatterlist */
	cur_page = 0;
	for_each_sg(sgt->sgl, s, sgt->orig_nents, i) {
		unsigned long chunk_size;
		unsigned int j;

		/* look for the end of the current chunk */
		for (j = cur_page + 1; j < n_pages; ++j)
			if (page_to_pfn(pages[j]) !=
			    page_to_pfn(pages[j - 1]) + 1)
				break;

		chunk_size = ((j - cur_page) << PAGE_SHIFT) - offset;
		sg_set_page(s, pages[cur_page], min(size, chunk_size), offset);
		size -= chunk_size;
		offset = 0;
		cur_page = j;
	}

	return 0;
}

#endif
#if (LINUX_VERSION_CODE < KERNEL_VERSION(3, 9, 0))

static int sg_page_count(struct scatterlist *sg)
{
	return PAGE_ALIGN(sg->offset + sg->length) >> PAGE_SHIFT;
}

void __sg_page_iter_start(struct sg_page_iter *piter,
			  struct scatterlist *sglist, unsigned int nents,
			  unsigned long pgoffset)
{
	piter->__pg_advance = 0;
	piter->__nents = nents;

	piter->sg = sglist;
	piter->sg_pgoffset = pgoffset;
}

bool __sg_page_iter_next(struct sg_page_iter *piter)
{
	if (!piter->__nents || !piter->sg)
		return false;

	piter->sg_pgoffset += piter->__pg_advance;
	piter->__pg_advance = 1;

	while (piter->sg_pgoffset >= sg_page_count(piter->sg)) {
		piter->sg_pgoffset -= sg_page_count(piter->sg);
		piter->sg = sg_next(piter->sg);
		if (!--piter->__nents || !piter->sg)
			return false;
	}

	return true;
}
#endif

#if (LINUX_VERSION_CODE < KERNEL_VERSION(4, 5, 0))
/**
 * memdup_user_nul - duplicate memory region from user space and NUL-terminate
 *
 * @src: source address in user space
 * @len: number of bytes to copy
 *
 * Returns an ERR_PTR() on failure.
 */
void *memdup_user_nul(const void __user *src, size_t len)
{
	char *p;

	/*
	 * Always use GFP_KERNEL, since copy_from_user() can sleep and
	 * cause pagefault, which makes it pointless to use GFP_NOFS
	 * or GFP_ATOMIC.
	 */
	/* p = kmalloc_track_caller(len + 1, GFP_KERNEL); */
	p = kmalloc(len + 1, GFP_KERNEL);
	if (!p)
		return ERR_PTR(-ENOMEM);

	if (copy_from_user(p, src, len)) {
		kfree(p);
		return ERR_PTR(-EFAULT);
	}
	p[len] = '\0';

	return p;
}
EXPORT_SYMBOL(memdup_user_nul);
#endif

#ifdef DMA_BUF_STANDALONE
#include <linux/file.h>
#include <linux/anon_inodes.h>
#include <linux/fdtable.h>
#include <linux/sched.h>

static int dma_buf_release(struct inode *inode, struct file *file);

static const struct file_operations dma_buf_fops = {
	.release	= dma_buf_release,
};

static int is_dma_buf_file(struct file *file)
{
	return file->f_op == &dma_buf_fops;
}

static int dma_buf_release(struct inode *inode, struct file *file)
{
	struct dma_buf *dmabuf;

	if (!is_dma_buf_file(file))
		return -EINVAL;

	dmabuf = file->private_data;
	dmabuf->ops->release(dmabuf);

	kfree(dmabuf);
	return 0;
}

struct dma_buf *dma_buf_export(void *priv, const struct dma_buf_ops *ops,
			       size_t size, int flags)
{
	struct dma_buf *dmabuf;
	struct file *file;

	dmabuf = kzalloc(sizeof(struct dma_buf), GFP_KERNEL);
	if (dmabuf == NULL)
		return ERR_PTR(-ENOMEM);

	dmabuf->priv = priv;
	dmabuf->ops = ops;

	file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf, flags);
	if (IS_ERR(file)) {
		kfree(dmabuf);
		return ERR_CAST(file);
	}

	file->f_mode |= FMODE_LSEEK;
	dmabuf->file = file;

	return dmabuf;
}

void dma_buf_put(struct dma_buf *dmabuf)
{
	if (WARN_ON(!dmabuf || !dmabuf->file))
		return;

	fput(dmabuf->file);
}

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

	file = fget(fd);

	if (!file)
		return ERR_PTR(-EBADF);

	if (!is_dma_buf_file(file)) {
		fput(file);
		return ERR_PTR(-EINVAL);
	}

	return file->private_data;
}

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

	if (!dmabuf || !dmabuf->file)
		return -EINVAL;

	fd = get_unused_fd_flags(O_CLOEXEC);
	if (fd < 0)
		return fd;

	fd_install(fd, dmabuf->file);

	return fd;
}
#endif

#ifdef VMW_COMPAT_FD_FLAGS
static void compat_set_close_on_exec(unsigned int fd)
{
	struct files_struct *files = current->files;
	struct fdtable *fdt;
	spin_lock(&files->file_lock);
	fdt = files_fdtable(files);
	FD_SET(fd, fdt->close_on_exec);
	spin_unlock(&files->file_lock);
}

int vmw_get_unused_fd_flags(unsigned int flags)
{
	int fd = get_unused_fd();

	WARN_ON_ONCE(flags != O_CLOEXEC);
	if (fd < 0)
		return fd;

	/*
	 * We explicitly set close_on_exec here since the function
	 * get_unused_fd_flags() which is used in the core dma-buf
	 * implementation is not exported on early 3 series kernels.
	 */
	compat_set_close_on_exec(fd);
	return fd;
}
#endif

#ifdef VMW_IDA_SIMPLE
static DEFINE_SPINLOCK(simple_ida_lock);

/**
 * ida_simple_get - get a new id.
 * @ida: the (initialized) ida.
 * @start: the minimum id (inclusive, < 0x8000000)
 * @end: the maximum id (exclusive, < 0x8000000 or 0)
 * @gfp_mask: memory allocation flags
 *
 * Allocates an id in the range start <= id < end, or returns -ENOSPC.
 * On memory allocation failure, returns -ENOMEM.
 *
 * Compared to ida_get_new_above() this function does its own locking, and
 * should be used unless there are special requirements.
 *
 * Use ida_simple_remove() to get rid of an id.
 */
int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
		   gfp_t gfp_mask)
{
	int ret, id;
	unsigned int max;
	unsigned long flags;

	BUG_ON((int)start < 0);
	BUG_ON((int)end < 0);

	if (end == 0)
		max = 0x80000000;
	else {
		BUG_ON(end < start);
		max = end - 1;
	}

again:
	if (!ida_pre_get(ida, gfp_mask))
		return -ENOMEM;

	spin_lock_irqsave(&simple_ida_lock, flags);
	ret = ida_get_new_above(ida, start, &id);
	if (!ret) {
		if (id > max) {
			ida_remove(ida, id);
			ret = -ENOSPC;
		} else {
			ret = id;
		}
	}
	spin_unlock_irqrestore(&simple_ida_lock, flags);

	if (unlikely(ret == -EAGAIN))
		goto again;

	return ret;
}

/**
 * ida_simple_remove - remove an allocated id.
 * @ida: the (initialized) ida.
 * @id: the id returned by ida_simple_get.
 *
 * Use to release an id allocated with ida_simple_get().
 *
 * Compared to ida_remove() this function does its own locking, and should be
 * used unless there are special requirements.
 */
void ida_simple_remove(struct ida *ida, unsigned int id)
{
	unsigned long flags;

	BUG_ON((int)id < 0);
	spin_lock_irqsave(&simple_ida_lock, flags);
	ida_remove(ida, id);
	spin_unlock_irqrestore(&simple_ida_lock, flags);
}
#endif