From: Rafał Miłecki <rafal@milecki.pl>
Date: Sat, 23 Dec 2017 22:14:25 +0000 (+0100)
Subject: bcm53xx: use iflag=skip_bytes for dd command during sysupgrade
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=3267ce750e491ba0290ec3a9a5e3b4dceadd47a5;p=openwrt%2Fstaging%2Fadrian.git

bcm53xx: use iflag=skip_bytes for dd command during sysupgrade

Since BusyBox 1.25.0 dd command supports iflag=skip_bytes which allows
skipping requested amount of bytes without reducing blocksize. Thanks to
this we can leave default blocksize and let dd work more efficiently.

On Netgear R6250 "dd skip=58 iflag=skip_bytes" can be 5 times faster
than "dd bs=58 skip=1" when extracting TRX out of CHK.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
---

diff --git a/target/linux/bcm53xx/base-files/lib/upgrade/platform.sh b/target/linux/bcm53xx/base-files/lib/upgrade/platform.sh
index 1a33e3a447..06451f17fd 100644
--- a/target/linux/bcm53xx/base-files/lib/upgrade/platform.sh
+++ b/target/linux/bcm53xx/base-files/lib/upgrade/platform.sh
@@ -274,11 +274,11 @@ platform_pre_upgrade() {
 platform_trx_from_chk_cmd() {
 	local header_len=$((0x$(get_magic_long_at "$1" 4)))
 
-	echo -n dd bs=$header_len skip=1
+	echo -n dd skip=$header_len iflag=skip_bytes
 }
 
 platform_trx_from_cybertan_cmd() {
-	echo -n dd bs=32 skip=1
+	echo -n dd skip=32 iflag=skip_bytes
 }
 
 platform_img_from_safeloader() {