From f6e7be9a06bcb3157c18863b7831dba9af5f978e Mon Sep 17 00:00:00 2001
From: Benjamin Valentin <benpicco@googlemail.com>
Date: Mon, 4 Nov 2019 21:07:23 +0100
Subject: [PATCH] sys/luid: allow to overwrite luid_base()

This allows to overwrite luid_base() with a function that reads an
ID from e.g. a EUI64MAC chip if no CPU ID is available.
---
 sys/luid/luid.c | 37 ++++++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 17 deletions(-)

diff --git a/sys/luid/luid.c b/sys/luid/luid.c
index 1b7a876ce1..9810df5df3 100644
--- a/sys/luid/luid.c
+++ b/sys/luid/luid.c
@@ -26,7 +26,26 @@
 
 #include "luid.h"
 
-static uint8_t lastused = 1;
+#ifndef MAX
+#define MAX(a, b) (((a) > (b)) ? (a) : (b))
+#endif
+
+void __attribute__((weak)) luid_base(void *buf, size_t len)
+{
+    memset(buf, LUID_BACKUP_SEED, len);
+
+#if CPUID_LEN
+    uint8_t *out = (uint8_t *)buf;
+    uint8_t cid[CPUID_LEN];
+
+    cpuid_get(cid);
+    for (size_t i = 0; i < MAX(len, CPUID_LEN); i++) {
+        out[i % len] ^= cid[i % CPUID_LEN];
+    }
+#endif
+}
+
+static uint8_t lastused;
 
 void luid_get(void *buf, size_t len)
 {
@@ -44,19 +63,3 @@ void luid_custom(void *buf, size_t len, int gen)
     }
 }
 
-void luid_base(void *buf, size_t len)
-{
-    assert(buf && (len > 0));
-
-    memset(buf, LUID_BACKUP_SEED, len);
-
-#if CPUID_LEN
-    uint8_t *out = (uint8_t *)buf;
-    uint8_t cid[CPUID_LEN];
-
-    cpuid_get(cid);
-    for (size_t i = 0; i < CPUID_LEN; i++) {
-        out[i % len] ^= cid[i];
-    }
-#endif
-}