common: board_[read/write]_serial weak reference cleanup

board_read_serial and board_write_serial were prototyped as weak
and this made all instances, that included that prototype, weak
as well.  In order to not lose information from the prototype,
default and override functions, I changed to use the override
weak marker symbols.

These functions defaulted for specific configurations as
different functionality and used an #ifdef tree to do this. I
made these a single definition for each function and used
IS_ENABLED instead of the #ifdef tree.  I also added a
definition for the case that the configuration would not have
produced a function.

BUG=none
BRANCH=none
TEST=make buildall -j

Change-Id: Ie41c53f3a17d665358e46eefd3ded3066ee80a7d
Signed-off-by: Denis Brockus <dbrockus@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1631583
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-by: Jett Rink <jettrink@chromium.org>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Commit-Queue: Jett Rink <jettrink@chromium.org>

3 files changed, 21 insertions, 26 deletions

diff --git a/board/hammer/board.c b/board/hammer/board.c
index 8b3de4268c..6b7a4029cf 100644
--- a/board/hammer/board.c
+++ b/board/hammer/board.c
@@ -303,7 +303,7 @@ int board_get_entropy(void *buffer, int len)
 /*
  * Generate a USB serial number from unique chip ID.
  */
-const char *board_read_serial(void)
+__override const char *board_read_serial(void)
 {
 	static char str[CONFIG_SERIALNO_LEN];
 
@@ -322,7 +322,7 @@ const char *board_read_serial(void)
 	return str;
 }
 
-int board_write_serial(const char *serialno)
+__override int board_write_serial(const char *serialno)
 {
 	return 0;
 }
diff --git a/common/system.c b/common/system.c
index 39390a9418..2a7059d455 100644
--- a/common/system.c
+++ b/common/system.c
@@ -1589,33 +1589,27 @@ int system_can_boot_ap(void)
 
 #ifdef CONFIG_SERIALNO_LEN
 /* By default, read serial number from flash, can be overridden. */
-#if defined(CONFIG_FLASH_PSTATE) && defined(CONFIG_FLASH_PSTATE_BANK)
-__attribute__((weak))
-const char *board_read_serial(void)
-{
-	return flash_read_pstate_serial();
-}
-#elif defined(CONFIG_OTP)
-__attribute__((weak))
-const char *board_read_serial(void)
+__overridable const char *board_read_serial(void)
 {
-	return otp_read_serial();
+	if (IS_ENABLED(CONFIG_FLASH_PSTATE) &&
+	    IS_ENABLED(CONFIG_FLASH_PSTATE_BANK))
+		return flash_read_pstate_serial();
+	else if (IS_ENABLED(CONFIG_OTP))
+		return otp_read_serial();
+	else
+		return "";
 }
-#endif
 
-#if defined(CONFIG_FLASH_PSTATE) && defined(CONFIG_FLASH_PSTATE_BANK)
-__attribute__((weak))
-int board_write_serial(const char *serialno)
-{
-	return flash_write_pstate_serial(serialno);
-}
-#elif defined(CONFIG_OTP)
-__attribute__((weak))
-int board_write_serial(const char *serialno)
+__overridable int board_write_serial(const char *serialno)
 {
-	return otp_write_serial(serialno);
+	if (IS_ENABLED(CONFIG_FLASH_PSTATE) &&
+	    IS_ENABLED(CONFIG_FLASH_PSTATE_BANK))
+		return flash_write_pstate_serial(serialno);
+	else if (IS_ENABLED(CONFIG_OTP))
+		return otp_write_serial(serialno);
+	else
+		return EC_ERROR_UNIMPLEMENTED;
 }
-#endif
 #endif  /* CONFIG_SERIALNO_LEN */
 
 
diff --git a/include/system.h b/include/system.h
index e1eec86998..17419007db 100644
--- a/include/system.h
+++ b/include/system.h
@@ -327,13 +327,14 @@ int system_get_chip_unique_id(uint8_t **id);
  * Optional board-level callback functions to read a unique serial number per
  * chip. Default implementation reads from flash/otp (flash/otp_read_serial).
  */
-const char *board_read_serial(void) __attribute__((weak));
+__override_proto const char *board_read_serial(void);
 
 /**
  * Optional board-level callback functions to write a unique serial number per
  * chip. Default implementation reads from flash/otp (flash/otp_write_serial).
  */
-int board_write_serial(const char *serial) __attribute__((weak));
+__override_proto int board_write_serial(const char *serial);
+
 /*
  * Common bbram entries. Chips don't necessarily need to implement
  * all of these, error will be returned from system_get/set_bbram if