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 1a33e3a447273357f16b716df3b881fc02c87718..06451f17fd91a50e4ab4d358200347b94afbaeb7 100644 (file)
--- 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() {