1 files changed, 47 insertions, 0 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 13cbc420fead..ba94dec5b259 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2393,6 +2393,53 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
 }
 EXPORT_SYMBOL(remap_pfn_range);
 
+/**
+ * vm_iomap_memory - remap memory to userspace
+ * @vma: user vma to map to
+ * @start: start of area
+ * @len: size of area
+ *
+ * This is a simplified io_remap_pfn_range() for common driver use. The
+ * driver just needs to give us the physical memory range to be mapped,
+ * we'll figure out the rest from the vma information.
+ *
+ * NOTE! Some drivers might want to tweak vma->vm_page_prot first to get
+ * whatever write-combining details or similar.
+ */
+int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len)
+{
+        unsigned long vm_len, pfn, pages;
+
+        /* Check that the physical memory area passed in looks valid */
+        if (start + len < start)
+                return -EINVAL;
+        /*
+         * You *really* shouldn't map things that aren't page-aligned,
+         * but we've historically allowed it because IO memory might
+         * just have smaller alignment.
+         */
+        len += start & ~PAGE_MASK;
+        pfn = start >> PAGE_SHIFT;
+        pages = (len + ~PAGE_MASK) >> PAGE_SHIFT;
+        if (pfn + pages < pfn)
+                return -EINVAL;
+
+        /* We start the mapping 'vm_pgoff' pages into the area */
+        if (vma->vm_pgoff > pages)
+                return -EINVAL;
+        pfn += vma->vm_pgoff;
+        pages -= vma->vm_pgoff;
+
+        /* Can we fit all of the mapping? */
+        vm_len = vma->vm_end - vma->vm_start;
+        if (vm_len >> PAGE_SHIFT > pages)
+                return -EINVAL;
+
+        /* Ok, let it rip */
+        return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot);
+}
+EXPORT_SYMBOL(vm_iomap_memory);
+
 static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
                                      unsigned long addr, unsigned long end,
                                      pte_fn_t fn, void *data)