[src/trunk]: src/sys/external/bsd/drm2/include/linux Fix indexing convention ...

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/dcef5cb5866b
branches:  trunk
changeset: 340952:dcef5cb5866b
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Tue Oct 13 00:42:20 2015 +0000

description:
Fix indexing convention of Linux __ffs/__ffs64 shims.

They reject zero input, and yield zero-based indexing, unlike our
ffs/ffs64, which return zero for zero and yield one-based indexing.

May let nouveau make a little more progress toward booting!

Found by mrg@.

diffstat:

 sys/external/bsd/drm2/include/linux/bitops.h |  14 +++++++++++---
 1 files changed, 11 insertions(+), 3 deletions(-)

diffs (36 lines):

diff -r 287811f7e9af -r dcef5cb5866b sys/external/bsd/drm2/include/linux/bitops.h
--- a/sys/external/bsd/drm2/include/linux/bitops.h      Tue Oct 13 00:29:34 2015 +0000
+++ b/sys/external/bsd/drm2/include/linux/bitops.h      Tue Oct 13 00:42:20 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: bitops.h,v 1.9 2015/02/25 15:40:20 riastradh Exp $     */
+/*     $NetBSD: bitops.h,v 1.10 2015/10/13 00:42:20 riastradh Exp $    */
 
 /*-
  * Copyright (c) 2013 The NetBSD Foundation, Inc.
@@ -42,16 +42,24 @@
 
 #include <lib/libkern/libkern.h>
 
+/*
+ * Linux __ffs/__ffs64 is zero-based; zero input is undefined.  Our
+ * ffs/ffs is one-based; zero input yields zero.
+ */
 static inline unsigned long
 __ffs(unsigned long x)
 {
-       return ffs64(x);
+
+       KASSERT(x != 0);
+       return ffs64(x) - 1;
 }
 
 static inline unsigned long
 __ffs64(uint64_t x)
 {
-       return ffs64(x);
+
+       KASSERT(x != 0);
+       return ffs64(x) - 1;
 }
 
 static inline unsigned int