[src/trunk]: src/sys/external/bsd/drm2/include/linux Try setting and clearing...

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

details:   https://anonhg.NetBSD.org/src/rev/57263210bc85
branches:  trunk
changeset: 835406:57263210bc85
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Mon Aug 27 14:50:24 2018 +0000

description:
Try setting and clearing the bits we meant, not other bits.

Fix comments to match intent while we're fixing reality too.

diffstat:

 sys/external/bsd/drm2/include/linux/bitmap.h |  37 +++++++++++++++------------
 1 files changed, 20 insertions(+), 17 deletions(-)

diffs (73 lines):

diff -r 6a8ab9761411 -r 57263210bc85 sys/external/bsd/drm2/include/linux/bitmap.h
--- a/sys/external/bsd/drm2/include/linux/bitmap.h      Mon Aug 27 14:50:04 2018 +0000
+++ b/sys/external/bsd/drm2/include/linux/bitmap.h      Mon Aug 27 14:50:24 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: bitmap.h,v 1.3 2018/08/27 07:13:45 riastradh Exp $     */
+/*     $NetBSD: bitmap.h,v 1.4 2018/08/27 14:50:24 riastradh Exp $     */
 
 /*-
  * Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -96,44 +96,47 @@
 /*
  * bitmap_set(bitmap, startbit, nbits)
  *
- *     Set bits at startbit, startbit+1, ..., nbits-2, nbits-1 to 1.
+ *     Set bits at startbit, startbit+1, ..., startbit+nbits-2,
+ *     startbit+nbits-1 to 1.
  */
 static inline void
 bitmap_set(unsigned long *bitmap, size_t startbit, size_t nbits)
 {
        const size_t bpl = NBBY * sizeof(*bitmap);
-       unsigned long *p;
+       unsigned long *p = bitmap + startbit/bpl;
        unsigned long mask;
+       unsigned sz;
 
-       for (p = bitmap + startbit/bpl, mask = ~(~0UL << (startbit%bpl));
-            nbits >= bpl;
-            p++, nbits -= bpl, mask = ~0UL)
-               *p |= mask;
+       for (sz = bpl - (startbit%bpl), mask = ~0UL << (startbit%bpl);
+            nbits >= sz;
+            nbits -= sz, sz = bpl, mask = ~0UL)
+               *p++ |= mask;
 
        if (nbits)
-               *p |= mask & (~0UL << nbits);
+               *p |= mask & ~(~0UL << (nbits + bpl - sz));
 }
 
 /*
- * bitmap_set(bitmap, startbit, nbits)
+ * bitmap_clear(bitmap, startbit, nbits)
  *
- *     Clear bits at startbit, startbit+1, ..., nbits-2, nbits-1,
- *     replacing them by 0.
+ *     Clear bits at startbit, startbit+1, ..., startbit+nbits-2,
+ *     startbit+nbits-1, replacing them by 0.
  */
 static inline void
 bitmap_clear(unsigned long *bitmap, size_t startbit, size_t nbits)
 {
        const size_t bpl = NBBY * sizeof(*bitmap);
-       unsigned long *p;
+       unsigned long *p = bitmap + startbit/bpl;
        unsigned long mask;
+       unsigned sz;
 
-       for (p = bitmap + startbit/bpl, mask = ~0UL << (startbit%bpl);
-            nbits >= bpl;
-            p++, nbits -= bpl, mask = 0UL)
-               *p &= mask;
+       for (sz = bpl - (startbit%bpl), mask = ~(~0UL << (startbit%bpl));
+            nbits >= sz;
+            nbits -= sz, sz = bpl, mask = 0UL)
+               *p++ &= mask;
 
        if (nbits)
-               *p &= mask | ~(~0UL << nbits);
+               *p &= mask | (~0UL << (nbits + bpl - sz));
 }
 
 /*