From ef82c280fd63448b3f8199a53ecc7768e393ecdc Mon Sep 17 00:00:00 2001
From: Gregory Nutt <gnutt@nuttx.org>
Date: Sun, 2 Nov 2014 12:11:20 -0600
Subject: [PATCH] MM: Minimum memory allocation must to up to 32 if sizeof
 pointer is 8-bytes

---
 arch/sim/include/limits.h | 11 +++++++---
 include/nuttx/mm/mm.h     | 42 +++++++++++++++++++++++++++++----------
 2 files changed, 39 insertions(+), 14 deletions(-)

diff --git a/arch/sim/include/limits.h b/arch/sim/include/limits.h
index 5a8d7c54e8..fabb97d8ee 100644
--- a/arch/sim/include/limits.h
+++ b/arch/sim/include/limits.h
@@ -77,10 +77,15 @@
 #define LLONG_MAX   9223372036854775807LL
 #define ULLONG_MAX  18446744073709551615ULL
 
-/* A pointer is 4 bytes */
+/* A pointer is 4 or 8 bytes */
 
 #define PTR_MIN     (-PTR_MAX - 1)
-#define PTR_MAX     2147483647
-#define UPTR_MAX    4294967295U
+#if !defined(CONFIG_HOST_X86_64) || defined(CONFIG_SIM_M32)
+#  define PTR_MAX   2147483647
+#  define UPTR_MAX  4294967295U
+#else
+#  define PTR_MAX   9223372036854775807LL
+#  define UPTR_MAX  18446744073709551615ULL
+#endif
 
 #endif /* __ARCH_SIM_INCLUDE_LIMITS_H  */
diff --git a/include/nuttx/mm/mm.h b/include/nuttx/mm/mm.h
index 707d7f7daa..97c260f501 100644
--- a/include/nuttx/mm/mm.h
+++ b/include/nuttx/mm/mm.h
@@ -112,24 +112,44 @@
 /* These definitions define the characteristics of allocator
  *
  * MM_MIN_SHIFT is used to define MM_MIN_CHUNK.
- * MM_MIN_CHUNK - is the smallest physical chunk that can
- *   be allocated.  It must be at least a large as
- *   sizeof(struct mm_freenode_s).  Larger values may
- *   improve performance slightly, but will waste memory
- *   due to quantization losses.
+ * MM_MIN_CHUNK - is the smallest physical chunk that can be allocated.  It
+ *   must be at least a large as sizeof(struct mm_freenode_s).  Larger values
+ *   may improve performance slightly, but will waste memory due to
+ *   quantization losses.
  *
  * MM_MAX_SHIFT is used to define MM_MAX_CHUNK
- * MM_MAX_CHUNK is the largest, contiguous chunk of memory
- *   that can be allocated.  It can range from 16-bytes to
- *   4Gb.  Larger values of MM_MAX_SHIFT can cause larger
- *   data structure sizes and, perhaps, minor performance
- *   losses.
+ * MM_MAX_CHUNK is the largest, contiguous chunk of memory that can be
+ *   allocated.  It can range from 16-bytes to 4Gb.  Larger values of
+ *   MM_MAX_SHIFT can cause larger data structure sizes and, perhaps,
+ *   minor performance losses.
+ */
+
+#if defined(CONFIG_MM_SMALL) && UINTPTR_MAX <= UINT32_MAX
+/* Two byte offsets; Pointers may be 2 or 4 bytes;
+ * sizeof(struct mm_freenode_s) is 8 or 12 bytes.
+ * REVISIT: We could do better on machines with 16-bit addressing.
  */
 
-#ifdef CONFIG_MM_SMALL
 #  define MM_MIN_SHIFT    4  /* 16 bytes */
 #  define MM_MAX_SHIFT   15  /* 32 Kb */
+
+#elif defined(CONFIG_HAVE_LONG_LONG)
+/* Four byte offsets; Pointers may be 4 or 8 bytes
+ * sizeof(struct mm_freenode_s) is 16 or 24 bytes.
+ */
+  
+#  if UINTPTR_MAX <= UINT32_MAX
+#    define MM_MIN_SHIFT  4  /* 16 bytes */
+#  elif UINTPTR_MAX <= UINT64_MAX
+#    define MM_MIN_SHIFT  5  /* 32 bytes */
+#  endif
+#  define MM_MAX_SHIFT   22  /*  4 Mb */
+
 #else
+/* Four byte offsets; Pointers must be 4 bytes.
+ * sizeof(struct mm_freenode_s) is 16 bytes.
+ */
+
 #  define MM_MIN_SHIFT    4  /* 16 bytes */
 #  define MM_MAX_SHIFT   22  /*  4 Mb */
 #endif