From: Julien Grall <julien.grall@arm.com>
Date: Fri, 22 Apr 2016 15:58:32 +0000 (+0100)
Subject: xen/bitops: Introduce GENMASK to generate mask
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~1226
X-Git-Url: https://dgit.raspbian.org/%22http://www.example.com/cgi/%22/%22http:/www.example.com/cgi/%22?a=commitdiff_plain;h=edd429c9cc2af99df9dda10002cc59011edf0cac;p=xen.git

xen/bitops: Introduce GENMASK to generate mask

The code has been imported from the header include/linux/bitops.h in
Linux v4.6-rc3.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
---

diff --git a/xen/include/xen/bitops.h b/xen/include/xen/bitops.h
index cb56f247ab..bd0883ab22 100644
--- a/xen/include/xen/bitops.h
+++ b/xen/include/xen/bitops.h
@@ -2,6 +2,14 @@
 #define _LINUX_BITOPS_H
 #include <asm/types.h>
 
+/*
+ * Create a contiguous bitmask starting at bit position @l and ending at
+ * position @h. For example
+ * GENMASK(30, 21) gives us the 32bit vector 0x01fe00000.
+ */
+#define GENMASK(h, l) \
+    (((~0UL) << (l)) & (~0UL >> (BITS_PER_LONG - 1 - (h))))
+
 /*
  * ffs: find first bit set. This is defined the same way as
  * the libc and compiler builtin ffs routines, therefore