drm/omap: Use drm_gem_mmap_obj() to implement dma-buf mmap

The dma-buf mmap code was copied from the GEM mmap implementation.
Replace it with the new drm_gem_mmap_obj() function.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c

@@ -136,10 +136,6 @@ static void omap_gem_dmabuf_kunmap(struct dma_buf *buffer,
 	kunmap(pages[page_num]);
 }
 
-/*
- * TODO maybe we can split up drm_gem_mmap to avoid duplicating
- * some here.. or at least have a drm_dmabuf_mmap helper.
- */
 static int omap_gem_dmabuf_mmap(struct dma_buf *buffer,
 		struct vm_area_struct *vma)
 {
@@ -149,31 +145,9 @@ static int omap_gem_dmabuf_mmap(struct dma_buf *buffer,
 	if (WARN_ON(!obj->filp))
 		return -EINVAL;
 
-	/* Check for valid size. */
-	if (omap_gem_mmap_size(obj) < vma->vm_end - vma->vm_start) {
-		ret = -EINVAL;
-		goto out_unlock;
-	}
-
-	if (!obj->dev->driver->gem_vm_ops) {
-		ret = -EINVAL;
-		goto out_unlock;
-	}
-
-	vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
-	vma->vm_ops = obj->dev->driver->gem_vm_ops;
-	vma->vm_private_data = obj;
-	vma->vm_page_prot =  pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
-
-	/* Take a ref for this mapping of the object, so that the fault
-	 * handler can dereference the mmap offset's pointer to the object.
-	 * This reference is cleaned up by the corresponding vm_close
-	 * (which should happen whether the vma was created by this call, or
-	 * by a vm_open due to mremap or partial unmap or whatever).
-	 */
-	vma->vm_ops->open(vma);
-
-out_unlock:
+	ret = drm_gem_mmap_obj(obj, omap_gem_mmap_size(obj), vma);
+	if (ret < 0)
+		return ret;
 
 	return omap_gem_mmap_obj(obj, vma);
 }