[PATCHv2 9/9] v4l: vb2-dma-contig: use dma_get_sgtable

[Tomasz Stanislawski]

This patch removes a workaround for extraction of struct pages
from DMA buffer. The method of using follow_pfn for artificial
VMA is dropped in favour of dma_get_sgtable function.

Signed-off-by: Tomasz Stanislawski <t.stanislaws at samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park at samsung.com>
---
 drivers/media/video/videobuf2-dma-contig.c |   60 ++--------------------------
 1 file changed, 4 insertions(+), 56 deletions(-)

diff --git a/drivers/media/video/videobuf2-dma-contig.c b/drivers/media/video/videobuf2-dma-contig.c
index a845ff7..73297b7 100644
--- a/drivers/media/video/videobuf2-dma-contig.c
+++ b/drivers/media/video/videobuf2-dma-contig.c
@@ -361,73 +361,21 @@ static struct dma_buf_ops vb2_dc_dmabuf_ops = {
 	.release = vb2_dc_dmabuf_ops_release,
 };
 
-/**
- * vb2_dc_kaddr_to_pages() - extract list of struct pages from a kernel
- * pointer.  This function is a workaround to extract pages from a pointer
- * returned by dma_alloc_coherent. The pages are obtained by creating an
- * artificial vma and using follow_pfn to do a page walk to find a PFN
- */
-static int vb2_dc_kaddr_to_pages(unsigned long kaddr,
-	struct page **pages, unsigned int n_pages)
-{
-	unsigned int i;
-	unsigned long pfn;
-	/* create an artificial VMA */
-	struct vm_area_struct vma = {
-		.vm_flags = VM_IO | VM_PFNMAP,
-		.vm_mm = &init_mm,
-	};
-
-	for (i = 0; i < n_pages; ++i, kaddr += PAGE_SIZE) {
-		if (follow_pfn(&vma, kaddr, &pfn))
-			break;
-		pages[i] = pfn_to_page(pfn);
-	}
-
-	return i;
-}
-
 static struct sg_table *vb2_dc_get_base_sgt(struct vb2_dc_buf *buf)
 {
-	int n_pages;
-	struct page **pages = NULL;
 	int ret;
 	struct sg_table *sgt;
 
-	n_pages = PAGE_ALIGN(buf->size) >> PAGE_SHIFT;
-
-	pages = kmalloc(n_pages * sizeof pages[0], GFP_KERNEL);
-	if (!pages) {
-		dev_err(buf->dev, "failed to alloc page table\n");
-		return ERR_PTR(-ENOMEM);
-	}
-
-	ret = vb2_dc_kaddr_to_pages((unsigned long)buf->vaddr, pages, n_pages);
-	if (ret < 0) {
-		dev_err(buf->dev, "failed to get buffer pages from DMA API\n");
-		kfree(pages);
-		return ERR_PTR(ret);
-	}
-	if (ret != n_pages) {
-		dev_err(buf->dev, "got only %d of %d pages from DMA API\n",
-			ret, n_pages);
-		kfree(pages);
-		return ERR_PTR(-EFAULT);
-	}
-
 	sgt = kmalloc(sizeof *sgt, GFP_KERNEL);
 	if (!sgt) {
 		dev_err(buf->dev, "failed to alloc sg table\n");
-		kfree(pages);
 		return ERR_PTR(-ENOMEM);
 	}
 
-	ret = sg_alloc_table_from_pages(sgt, pages, n_pages, 0,
-		buf->size, GFP_KERNEL);
-	/* failure or not, pages are no longer needed */
-	kfree(pages);
-	if (ret) {
-		dev_err(buf->dev, "failed to covert pages to sg table\n");
+	ret = dma_get_sgtable(buf->dev, sgt, buf->vaddr, buf->dma_addr,
+		buf->size, NULL);
+	if (ret < 0) {
+		dev_err(buf->dev, "failed to get scatterlist from DMA API\n");
 		kfree(sgt);
 		return ERR_PTR(ret);
 	}
-- 
1.7.9.5