[PATCH] v4l2: vb2: use dma_get_sgtable

[Subash Patel]

This is patch to remove vb2_dc_kaddr_to_pages() function with dma_get_sgtable()
in the patch set posted by Tomasz. It was observed that the former function
fails to get the pages, as follow_pfn() can fail for remapped kernel va provided
by the dma-mapping sub-system.

As Tomasz mentioned, the later call was temporary patch until dma-mapping author
finalizes the implementation of dma_get_sgtable(). One can use this patch to use
this vb2 patch-set for his/her work in the meantime.

Signed-off-by: Subash Patel <subash.ramaswamy at linaro.org>
---
 drivers/media/video/videobuf2-dma-contig.c |   53 ++-------------------------
 1 files changed, 4 insertions(+), 49 deletions(-)

diff --git a/drivers/media/video/videobuf2-dma-contig.c b/drivers/media/video/videobuf2-dma-contig.c
index e8da7f1..1b9023a 100644
--- a/drivers/media/video/videobuf2-dma-contig.c
+++ b/drivers/media/video/videobuf2-dma-contig.c
@@ -143,32 +143,11 @@ static void vb2_dc_put(void *buf_priv)
 	kfree(buf);
 }
 
-static int vb2_dc_kaddr_to_pages(unsigned long kaddr,
-	struct page **pages, unsigned int n_pages)
-{
-	unsigned int i;
-	unsigned long pfn;
-	struct vm_area_struct vma = {
-		.vm_flags = VM_IO | VM_PFNMAP,
-		.vm_mm = current->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 void *vb2_dc_alloc(void *alloc_ctx, unsigned long size)
 {
 	struct device *dev = alloc_ctx;
 	struct vb2_dc_buf *buf;
 	int ret = -ENOMEM;
-	int n_pages;
-	struct page **pages = NULL;
 
 	buf = kzalloc(sizeof *buf, GFP_KERNEL);
 	if (!buf)
@@ -183,35 +162,14 @@ static void *vb2_dc_alloc(void *alloc_ctx, unsigned long size)
 	WARN_ON((unsigned long)buf->vaddr & ~PAGE_MASK);
 	WARN_ON(buf->dma_addr & ~PAGE_MASK);
 
-	n_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
+	ret = dma_get_sgtable(dev, &buf->sgt_base, buf->vaddr,
+						buf->dma_addr, size, NULL);
 
-	pages = kmalloc(n_pages * sizeof pages[0], GFP_KERNEL);
-	if (!pages) {
-		dev_err(dev, "failed to alloc page table\n");
-		goto fail_dma;
-	}
-
-	ret = vb2_dc_kaddr_to_pages((unsigned long)buf->vaddr, pages, n_pages);
 	if (ret < 0) {
-		dev_err(dev, "failed to get buffer pages from DMA API\n");
-		goto fail_pages;
-	}
-	if (ret != n_pages) {
-		ret = -EFAULT;
-		dev_err(dev, "failed to get all pages from DMA API\n");
-		goto fail_pages;
-	}
-
-	ret = sg_alloc_table_from_pages(&buf->sgt_base,
-		pages, n_pages, 0, size, GFP_KERNEL);
-	if (ret) {
-		dev_err(dev, "failed to prepare sg table\n");
-		goto fail_pages;
+		dev_err(dev, "failed to get the SGT for the allocated pages\n");
+		goto fail_dma;
 	}
 
-	/* pages are no longer needed */
-	kfree(pages);
-
 	buf->dev = dev;
 	buf->size = size;
 
@@ -223,9 +181,6 @@ static void *vb2_dc_alloc(void *alloc_ctx, unsigned long size)
 
 	return buf;
 
-fail_pages:
-	kfree(pages);
-
 fail_dma:
 	dma_free_coherent(dev, size, buf->vaddr, buf->dma_addr);
 
-- 
1.7.5.4


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