/*
   * Copyright(c) 2004 - 2006 Intel Corporation. All rights reserved.
   * Portions based on net/core/datagram.c and copyrighted by their authors.
   *
   * 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.
   *
   * You should have received a copy of the GNU General Public License along with
   * this program; if not, write to the Free Software Foundation, Inc., 59
   * Temple Place - Suite 330, Boston, MA  02111-1307, USA.
   *
   * The full GNU General Public License is included in this distribution in the
   * file called COPYING.
   */
  
  /*
   * This code allows the net stack to make use of a DMA engine for
   * skb to iovec copies.
   */
  
  #include <linux/dmaengine.h>
  #include <linux/pagemap.h>
  #include <linux/slab.h>
  #include <net/tcp.h> /* for memcpy_toiovec */
  #include <asm/io.h>
  #include <asm/uaccess.h>
  
  static int num_pages_spanned(struct iovec *iov)
  {
  	return
  	((PAGE_ALIGN((unsigned long)iov->iov_base + iov->iov_len) -
  	((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT);
  }
  
  /*
   * Pin down all the iovec pages needed for len bytes.
   * Return a struct dma_pinned_list to keep track of pages pinned down.
   *
   * We are allocating a single chunk of memory, and then carving it up into
   * 3 sections, the latter 2 whose size depends on the number of iovecs and the
   * total number of pages, respectively.
   */
  struct dma_pinned_list *dma_pin_iovec_pages(struct iovec *iov, size_t len)
  {
  	struct dma_pinned_list *local_list;
  	struct page **pages;
  	int i;
  	int ret;
  	int nr_iovecs = 0;
  	int iovec_len_used = 0;
  	int iovec_pages_used = 0;
  
  	/* don't pin down non-user-based iovecs */
  	if (segment_eq(get_fs(), KERNEL_DS))
  		return NULL;
  
  	/* determine how many iovecs/pages there are, up front */
  	do {
  		iovec_len_used += iov[nr_iovecs].iov_len;
  		iovec_pages_used += num_pages_spanned(&iov[nr_iovecs]);
  		nr_iovecs++;
  	} while (iovec_len_used < len);
  
  	/* single kmalloc for pinned list, page_list[], and the page arrays */
  	local_list = kmalloc(sizeof(*local_list)
  		+ (nr_iovecs * sizeof (struct dma_page_list))
  		+ (iovec_pages_used * sizeof (struct page*)), GFP_KERNEL);
  	if (!local_list)
  		goto out;
  
  	/* list of pages starts right after the page list array */
  	pages = (struct page **) &local_list->page_list[nr_iovecs];
  
  	local_list->nr_iovecs = 0;
  
  	for (i = 0; i < nr_iovecs; i++) {
  		struct dma_page_list *page_list = &local_list->page_list[i];
  
  		len -= iov[i].iov_len;
  
  		if (!access_ok(VERIFY_WRITE, iov[i].iov_base, iov[i].iov_len))
  			goto unpin;
  
  		page_list->nr_pages = num_pages_spanned(&iov[i]);
  		page_list->base_address = iov[i].iov_base;
  
  		page_list->pages = pages;
  		pages += page_list->nr_pages;
  
  		/* pin pages down */
  		down_read(&current->mm->mmap_sem);
  		ret = get_user_pages(
  			current,
  			current->mm,
  			(unsigned long) iov[i].iov_base,
  			page_list->nr_pages,
  			1,	/* write */
  			0,	/* force */
  			page_list->pages,
  			NULL);
  		up_read(&current->mm->mmap_sem);
  
  		if (ret != page_list->nr_pages)
  			goto unpin;
  
  		local_list->nr_iovecs = i + 1;
  	}
  
  	return local_list;
  
  unpin:
  	dma_unpin_iovec_pages(local_list);
  out:
  	return NULL;
  }
  
  void dma_unpin_iovec_pages(struct dma_pinned_list *pinned_list)
  {
  	int i, j;
  
  	if (!pinned_list)
  		return;
  
  	for (i = 0; i < pinned_list->nr_iovecs; i++) {
  		struct dma_page_list *page_list = &pinned_list->page_list[i];
  		for (j = 0; j < page_list->nr_pages; j++) {
  			set_page_dirty_lock(page_list->pages[j]);
  			page_cache_release(page_list->pages[j]);
  		}
  	}
  
  	kfree(pinned_list);
  }
  
  
  /*
   * We have already pinned down the pages we will be using in the iovecs.
   * Each entry in iov array has corresponding entry in pinned_list->page_list.
   * Using array indexing to keep iov[] and page_list[] in sync.
   * Initial elements in iov array's iov->iov_len will be 0 if already copied into
   *   by another call.
   * iov array length remaining guaranteed to be bigger than len.
   */
  dma_cookie_t dma_memcpy_to_iovec(struct dma_chan *chan, struct iovec *iov,
  	struct dma_pinned_list *pinned_list, unsigned char *kdata, size_t len)
  {
  	int iov_byte_offset;
  	int copy;
  	dma_cookie_t dma_cookie = 0;
  	int iovec_idx;
  	int page_idx;
  
  	if (!chan)
  		return memcpy_toiovec(iov, kdata, len);
  
  	iovec_idx = 0;
  	while (iovec_idx < pinned_list->nr_iovecs) {
  		struct dma_page_list *page_list;
  
  		/* skip already used-up iovecs */
  		while (!iov[iovec_idx].iov_len)
  			iovec_idx++;
  
  		page_list = &pinned_list->page_list[iovec_idx];
  
  		iov_byte_offset = ((unsigned long)iov[iovec_idx].iov_base & ~PAGE_MASK);
  		page_idx = (((unsigned long)iov[iovec_idx].iov_base & PAGE_MASK)
  			 - ((unsigned long)page_list->base_address & PAGE_MASK)) >> PAGE_SHIFT;
  
  		/* break up copies to not cross page boundary */
  		while (iov[iovec_idx].iov_len) {
  			copy = min_t(int, PAGE_SIZE - iov_byte_offset, len);
  			copy = min_t(int, copy, iov[iovec_idx].iov_len);
  
  			dma_cookie = dma_async_memcpy_buf_to_pg(chan,
  					page_list->pages[page_idx],
  					iov_byte_offset,
  					kdata,
  					copy);
  			/* poll for a descriptor slot */
  			if (unlikely(dma_cookie < 0)) {
  				dma_async_issue_pending(chan);
  				continue;
  			}
  
  			len -= copy;
  			iov[iovec_idx].iov_len -= copy;
  			iov[iovec_idx].iov_base += copy;
  
  			if (!len)
  				return dma_cookie;
  
  			kdata += copy;
  			iov_byte_offset = 0;
  			page_idx++;
  		}
  		iovec_idx++;
  	}
  
  	/* really bad if we ever run out of iovecs */
  	BUG();
  	return -EFAULT;
  }
  
  dma_cookie_t dma_memcpy_pg_to_iovec(struct dma_chan *chan, struct iovec *iov,
  	struct dma_pinned_list *pinned_list, struct page *page,
  	unsigned int offset, size_t len)
  {
  	int iov_byte_offset;
  	int copy;
  	dma_cookie_t dma_cookie = 0;
  	int iovec_idx;
  	int page_idx;
  	int err;
  
  	/* this needs as-yet-unimplemented buf-to-buff, so punt. */
  	/* TODO: use dma for this */
  	if (!chan || !pinned_list) {
  		u8 *vaddr = kmap(page);
  		err = memcpy_toiovec(iov, vaddr + offset, len);
  		kunmap(page);
  		return err;
  	}
  
  	iovec_idx = 0;
  	while (iovec_idx < pinned_list->nr_iovecs) {
  		struct dma_page_list *page_list;
  
  		/* skip already used-up iovecs */
  		while (!iov[iovec_idx].iov_len)
  			iovec_idx++;
  
  		page_list = &pinned_list->page_list[iovec_idx];
  
  		iov_byte_offset = ((unsigned long)iov[iovec_idx].iov_base & ~PAGE_MASK);
  		page_idx = (((unsigned long)iov[iovec_idx].iov_base & PAGE_MASK)
  			 - ((unsigned long)page_list->base_address & PAGE_MASK)) >> PAGE_SHIFT;
  
  		/* break up copies to not cross page boundary */
  		while (iov[iovec_idx].iov_len) {
  			copy = min_t(int, PAGE_SIZE - iov_byte_offset, len);
  			copy = min_t(int, copy, iov[iovec_idx].iov_len);
  
  			dma_cookie = dma_async_memcpy_pg_to_pg(chan,
  					page_list->pages[page_idx],
  					iov_byte_offset,
  					page,
  					offset,
  					copy);
  			/* poll for a descriptor slot */
  			if (unlikely(dma_cookie < 0)) {
  				dma_async_issue_pending(chan);
  				continue;
  			}
  
  			len -= copy;
  			iov[iovec_idx].iov_len -= copy;
  			iov[iovec_idx].iov_base += copy;
  
  			if (!len)
  				return dma_cookie;
  
  			offset += copy;
  			iov_byte_offset = 0;
  			page_idx++;
  		}
  		iovec_idx++;
  	}
  
  	/* really bad if we ever run out of iovecs */
  	BUG();
  	return -EFAULT;
  }