V4L/DVB (13598): videobuf_dma_contig_user_get() for non-aligned offsets

If a USERPTR address that is not aligned to page boundary is passed to the
videobuf_dma_contig_user_get() function, it saves a page aligned address to
the dma_handle. This is not correct. This issue is observed when using USERPTR
IO machism for buffer exchange.

Updates from last version:-

Adding offset for size calculation as per comment from Magnus Damm. This
ensures the last page is also included for checking if memory is
contiguous.
Signed-off-by: Muralidharan Karicheri <m-karicheri2@ti.com>
Acked-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/videobuf-dma-contig.c

@@ -141,9 +141,11 @@ static int videobuf_dma_contig_user_get(struct videobuf_dma_contig_memory *mem,
 	struct vm_area_struct *vma;
 	unsigned long prev_pfn, this_pfn;
 	unsigned long pages_done, user_address;
+	unsigned int offset;
 	int ret;
 
-	mem->size = PAGE_ALIGN(vb->size);
+	offset = vb->baddr & ~PAGE_MASK;
+	mem->size = PAGE_ALIGN(vb->size + offset);
 	mem->is_userptr = 0;
 	ret = -EINVAL;
 
@@ -166,7 +168,7 @@ static int videobuf_dma_contig_user_get(struct videobuf_dma_contig_memory *mem,
 			break;
 
 		if (pages_done == 0)
-			mem->dma_handle = this_pfn << PAGE_SHIFT;
+			mem->dma_handle = (this_pfn << PAGE_SHIFT) + offset;
 		else if (this_pfn != (prev_pfn + 1))
 			ret = -EFAULT;