From: Josh Wu <josh.wu@atmel.com>
Date: Wed, 16 Sep 2015 10:21:04 +0000 (+0800)
Subject: tools: gen_eth_addr: add getpid() to time(0) to avoid duplicated seed
X-Git-Tag: v2015.10-rc4~3
X-Git-Url: https://git.sur5r.net/?a=commitdiff_plain;h=3e4dad50320d20894710276eb09f2057c6985065;p=u-boot

tools: gen_eth_addr: add getpid() to time(0) to avoid duplicated seed

As 'time(0) | getpid()' will have a lot of duplicated value. It is not a
expected behavior. We expect different value for the seed when when run
it in many times.

So this patch will left shift the getpid() and add to time(0). That
avoid duplicated value.

Test command is like:
  % RUN=0; while [ $RUN -lt 10000 ]; do
  tools/gen_eth_addr; RUN=$(($RUN+1)); done | sort | uniq | wc -l
  10000

This patch is incorporated with suggestions made by Wolfgang Denk and Andreas
Bießmann. Thanks them a lot.

Signed-off-by: Josh Wu <josh.wu@atmel.com>
Acked-by: Andreas Bießmann <andreas.devel@googlemail.com>
Acked-by: Wolfgang Denk <wd@denx.de>
Tested-by: Wolfgang Denk <wd@denx.de>
---

diff --git a/tools/gen_eth_addr.c b/tools/gen_eth_addr.c
index bf9d935efd..5fa3e0cf56 100644
--- a/tools/gen_eth_addr.c
+++ b/tools/gen_eth_addr.c
@@ -15,7 +15,7 @@ main(int argc, char *argv[])
 {
     unsigned long ethaddr_low, ethaddr_high;
 
-    srand(time(0) | getpid());
+    srand(time(0) + (getpid() << 8));
 
     /*
      * setting the 2nd LSB in the most significant byte of