Change in coreboot[master]: mb/siemens/mc_apl1: Simplify is_mac_adr_valid() logic

[Patrick Georgi (Code Review)]

Patrick Georgi has submitted this change. ( https://review.coreboot.org/c/coreboot/+/47405 )

Change subject: mb/siemens/mc_apl1: Simplify is_mac_adr_valid() logic
......................................................................

mb/siemens/mc_apl1: Simplify is_mac_adr_valid() logic

A MAC address that is neither 00:00:00:00:00:00 nor ff:ff:ff:ff:ff:ff is
considered valid. Instead of using a temporary buffer and memcmp(), use
a single loop that exits as soon as the MAC cannot possibly be invalid.

Change-Id: I2b15b510092860fbbefd150c9060da38aeb13311
Signed-off-by: Angel Pons 
Reviewed-on: https://review.coreboot.org/c/coreboot/+/47405
Tested-by: build bot (Jenkins) 
Reviewed-by: Werner Zeh 
Reviewed-by: Mario Scheithauer 
Reviewed-by: Uwe Poeche 
---
M src/mainboard/siemens/mc_apl1/mainboard.c
1 file changed, 7 insertions(+), 9 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Werner Zeh: Looks good to me, approved
  Mario Scheithauer: Looks good to me, but someone else must approve
  Uwe Poeche: Looks good to me, but someone else must approve

diff --git a/src/mainboard/siemens/mc_apl1/mainboard.c b/src/mainboard/siemens/mc_apl1/mainboard.c
index ff0cc59..9540d6d 100644
--- a/src/mainboard/siemens/mc_apl1/mainboard.c
+++ b/src/mainboard/siemens/mc_apl1/mainboard.c
@@ -35,15 +35,13 @@
  */
 static uint8_t is_mac_adr_valid(uint8_t mac[MAC_ADDR_LEN])
 {
-	uint8_t buf[MAC_ADDR_LEN];
-
-	memset(buf, 0, sizeof(buf));
-	if (!memcmp(buf, mac, sizeof(buf)))
-		return 0;
-	memset(buf, 0xff, sizeof(buf));
-	if (!memcmp(buf, mac, sizeof(buf)))
-		return 0;
-	return 1;
+	for (size_t i = 0; i < MAC_ADDR_LEN; i++) {
+		if (mac[i] != 0x00 && mac[i] != 0xff)
+			return 1;
+		if (mac[i] != mac[0])
+			return 1;
+	}
+	return 0;
 }

/** \brief This function will search for a MAC address which can be assigned