libc/stream: Support lowsyslog.

This commit added support for lowsyslog.

Signed-off-by: ouyangxiangzhen <ouyangxiangzhen@xiaomi.com>

include/debug.h

@@ -29,6 +29,7 @@
 
 #include <nuttx/config.h>
 #include <nuttx/compiler.h>
+#include <nuttx/streams.h>
 
 #ifdef CONFIG_ARCH_DEBUG_H
 #  include <arch/debug.h>
@@ -1318,6 +1319,26 @@
 #  define resetinfodumpbuffer(m,b,n)
 #endif
 
+/****************************************************************************
+ * Name: lowsyslog
+ *
+ * Description:
+ *   lowsyslog() is used for output debug information at early boot-stage.
+ *
+ *   The NuttX implementation does not support any special formatting
+ *   characters beyond those supported by printf.
+ *
+ ****************************************************************************/
+
+#define lowsyslog(...) \
+  do \
+    { \
+       struct lib_outstream_s stream; \
+       lib_lowoutstream(&stream); \
+       lib_sprintf(&stream, __VA_ARGS__); \
+    } \
+  while (0)
+
 /****************************************************************************
  * Public Function Prototypes
  ****************************************************************************/

include/nuttx/arch.h

@@ -2820,6 +2820,18 @@ int arch_phy_irq(FAR const char *intf, xcpt_t handler, void *arg,
 
 void up_putc(int ch);
 
+/****************************************************************************
+ * Name: up_lowputc
+ *
+ * Description:
+ *   Output one character in early boot-stages.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_ARCH_LOWPUTC
+void up_lowputc(int ch);
+#endif
+
 /****************************************************************************
  * Name: up_puts
  *

libs/libc/stream/lib_lowoutstream.c

@@ -67,7 +67,7 @@ static void lowoutstream_putc(FAR struct lib_outstream_s *self, int ch)
 {
   DEBUGASSERT(self);
 
-  up_putc(ch);
+  up_lowputc(ch);
 
   if (ch != EOF)
     {
@@ -82,10 +82,16 @@ static void lowoutstream_putc(FAR struct lib_outstream_s *self, int ch)
 static ssize_t lowoutstream_puts(FAR struct lib_outstream_s *self,
                                  FAR const void *buf, size_t len)
 {
+  FAR const char *str = (FAR const char *)buf;
+  size_t idx          = 0;
   DEBUGASSERT(self);
 
-  self->nput += len;
+  while (str[idx] != 0 && idx < len)
-  up_nputs(buf, len);
+    {
+      lowoutstream_putc(self, str[idx]);
+      idx++;
+    }
+
   return len;
 }