1 files changed, 19 insertions, 6 deletions

diff --git a/drivers/char/bsr.c b/drivers/char/bsr.c
index 7d9fd8a8dfd0..c02db01f736e 100644
--- a/drivers/char/bsr.c
+++ b/drivers/char/bsr.c
@@ -27,6 +27,7 @@
 #include <linux/cdev.h>
 #include <linux/list.h>
 #include <linux/mm.h>
+#include <asm/pgtable.h>
 #include <asm/io.h>
 
 /*
@@ -118,15 +119,22 @@ static int bsr_mmap(struct file *filp, struct vm_area_struct *vma)
 {
         unsigned long size   = vma->vm_end - vma->vm_start;
         struct bsr_dev *dev = filp->private_data;
+        int ret;
 
-        if (size > dev->bsr_len || (size & (PAGE_SIZE-1)))
-                return -EINVAL;
-
-        vma->vm_flags |= (VM_IO | VM_DONTEXPAND);
         vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 
-        if (io_remap_pfn_range(vma, vma->vm_start, dev->bsr_addr >> PAGE_SHIFT,
-                               size, vma->vm_page_prot))
+        /* check for the case of a small BSR device and map one 4k page for it*/
+        if (dev->bsr_len < PAGE_SIZE && size == PAGE_SIZE)
+                ret = remap_4k_pfn(vma, vma->vm_start, dev->bsr_addr >> 12,
+                                   vma->vm_page_prot);
+        else if (size <= dev->bsr_len)
+                ret = io_remap_pfn_range(vma, vma->vm_start,
+                                         dev->bsr_addr >> PAGE_SHIFT,
+                                         size, vma->vm_page_prot);
+        else
+                return -EINVAL;
+
+        if (ret)
                 return -EAGAIN;
 
         return 0;
@@ -206,6 +214,11 @@ static int bsr_add_node(struct device_node *bn)
                 cur->bsr_stride = bsr_stride[i];
                 cur->bsr_dev    = MKDEV(bsr_major, i + total_bsr_devs);
 
+                /* if we have a bsr_len of > 4k and less then PAGE_SIZE (64k pages) */
+                /* we can only map 4k of it, so only advertise the 4k in sysfs */
+                if (cur->bsr_len > 4096 && cur->bsr_len < PAGE_SIZE)
+                        cur->bsr_len = 4096;
+
                 switch(cur->bsr_bytes) {
                 case 8:
                         cur->bsr_type = BSR_8;