Introduce debug macro hooks for AVR

When AVR_HAS_MEMX_PTR is enabled provide dbg macro hooks that place
the format strings in program memory releasing RAM for other tasks.

arch/avr/include/debug.h

@@ -0,0 +1,85 @@
+/****************************************************************************
+ * arch/avr/include/debug.h
+ *
+ *   Copyright (C) 2007-2011, 2014 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#ifndef __INCLUDE_ARCH_AVR_DEBUG_H
+#define __INCLUDE_ARCH_AVR_DEBUG_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#ifdef CONFIG_AVR_HAS_MEMX_PTR
+
+#include <nuttx/config.h>
+#include <nuttx/compiler.h>
+
+#include <syslog.h>
+
+
+/*
+ * Since format string that is passed to __arch_syslog() can be a 
+ * comma-separated list, we need some cpp trickery to handle it
+ *
+ * __dbg_first() helper macro accepts the format (that is potentially
+ * a comma-separated) and substitutes to its first element.
+ *
+ * __dbg_subst() helper macro substitutes first element in the format 
+ * with prefix.
+ */
+#define __dbg_first(format, ...) format
+#define __dbg_subst(prefix, format, ...) prefix, ##__VA_ARGS__
+
+#define __dbg_expand(logger, prio, format, ...) \
+ do { \
+   static const IOBJ char dbg_s[] = __dbg_first(format); \
+   logger(prio, __dbg_subst(dbg_s, format), ##__VA_ARGS__); \
+ } while(0)
+
+/*
+ * __arch_syslog() and __arch_lowsyslog() override behavior of NuttX
+ * dbg macros. They put the format string into program memory and
+ * utilize IPTR (__memx) parameter of syslog to take the format
+ * directly from program memory.  This reduces amount of RAM held by
+ * the format strings used in debug statements.
+ */
+#define __arch_syslog(...) \
+   __dbg_expand(syslog, ##__VA_ARGS__)  
+
+#define __arch_lowsyslog(...) \
+   __dbg_expand(lowsyslog, ##__VA_ARGS__)  
+
+#endif /* CONFIG_AVR_HAS_MEMX_PTR */
+
+#endif /* __INCLUDE_ARCH_DEBUG_H */

arch/avr/src/avr/Kconfig

@@ -73,6 +73,7 @@ menu "Atmel AVR Toolchain options"
 config AVR_HAS_MEMX_PTR
 	bool "Enable in-flash static const stings"
 	depends on AVR_ATMEL_AVR_TOOLCHAIN
+        select ARCH_DEBUG_H
 	default y
 	---help---
                 Enabling this option (recommended) will place all constant