zephyr: switch to using shell_*, not printk

Reimplement the printf functions for Zephyr to use shell_* functions
instead of printk.

The main differences are:
-UART output is buffered by the shell layer. The size of the buffer
should be adjusted per board (SHELL_BACKEND_SERIAL_TX_RING_BUFFER_SIZE)
-The shell uses non-blocking UART FIFO operations while printk waits
actively for every sent byte.
-The shell prints can not be split by the other shell prints so it
should increase the quality of the output. However the shell_* functions
can not be used in interrupts, so use printk instead which can divide
the shell output. The output may be messy for boards that have a lot
of prints in interrupts e.g. volteer.

EC uses unusual print format e.g. "%pT" to print a timestamp, so use the
CrosEC's vfnprintf function and then pass the generated string to the
shell_* print. Use the sprintf function for that purpose.
Long term, the EC codebase should switch to a usual print format,
so shell_* can be used directly and not 2 versions of vfnprintf.

This change should also help to pass tests that wait for a certain
pattern on output e.g. ECBootTime.

BUG=b:191724484, b:178033156
BRANCH=none
TEST=Verify the console output works

Signed-off-by: Dawid Niedzwiecki <dn@semihalf.com>
Change-Id: Ifaed2093ab8c43038c7d3e0ded1449a93f7f7da5
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2988194
Reviewed-by: Keith Short <keithshort@chromium.org>
Commit-Queue: Keith Short <keithshort@chromium.org>

1 files changed, 16 insertions, 3 deletions

diff --git a/include/printf.h b/include/printf.h
index 5c6373cf1e..37c0cc3949 100644
--- a/include/printf.h
+++ b/include/printf.h
@@ -12,6 +12,13 @@
 #include <stddef.h>  /* For size_t */
 #include "common.h"
 
+/* The declaration of snprintf is changed to crec_snprintf for Zephyr,
+ * so include stdio.h from Zephyr.
+ */
+#ifdef CONFIG_ZEPHYR
+#include <stdio.h>
+#endif
+
 /*
  * Printf formatting: % [flags] [width] [.precision] [length] [type]
  *
@@ -77,6 +84,11 @@
 __stdlib_compat int vfnprintf(int (*addchar)(void *context, int c),
 			      void *context, const char *format, va_list args);
 
+#ifndef CONFIG_ZEPHYR
+#define snprintf crec_snprintf
+#define vsnprintf crec_vsnprintf
+#endif
+
 /**
  * Print formatted outut to a string.
  *
@@ -88,7 +100,8 @@ __stdlib_compat int vfnprintf(int (*addchar)(void *context, int c),
  * @return EC_SUCCESS, or EC_ERROR_OVERFLOW if the output was truncated.
  */
 __attribute__((__format__(__printf__, 3, 4)))
-__stdlib_compat int snprintf(char *str, size_t size, const char *format, ...);
+__stdlib_compat int crec_snprintf(char *str, size_t size, const char *format,
+				  ...);
 
 /**
  * Print formatted output to a string.
@@ -102,8 +115,8 @@ __stdlib_compat int snprintf(char *str, size_t size, const char *format, ...);
  * @return The string length written to str, or a negative value on error.
  *         The negative values can be -EC_ERROR_INVAL or -EC_ERROR_OVERFLOW.
  */
-__stdlib_compat int vsnprintf(char *str, size_t size, const char *format,
-			      va_list args);
+__stdlib_compat int crec_vsnprintf(char *str, size_t size, const char *format,
+				   va_list args);
 
 #endif  /* !HIDE_EC_STDLIB */