[PATCH] realtek: fix ZyXEL initramfs image generation

[Bjørn Mork]

The current rule produces empty trailers, causing the OEM firmware
update application to reject our images.

The double expansion of a makefile variable does not work inside
shell code.  The second round is interpreted as a shell expansion,
attempting to run the command ZYXEL_VERS instead of expanding the
$(ZYXEL_VERS) makefile variable.

Fix by removing one level of variable indirection.

Fixes: c6c8d597e183 ("realtek: Add generic zyxel_gs1900 image definition")
Signed-off-by: Bjørn Mork <bjorn at mork.no>
---
I got myself another brand new GS1900-10HP and used the opportunity to
verify the console-less installation procedure.  And of course, it didn't
work....

The reason is that we currently build images with a bogus trailer,
lacking the crucial hardware version info the OEM firmware looks
for.

This needs to be backported yto 21.02 as well.  I dowloaded the
initramfs images from downloads.openwrt.org and verified that they have
the same issue:

 $ hexdump -C openwrt-21.02.0-rc3-realtek-generic-zyxel_gs1900-10hp-initramfs-kernel.bin |tail -4
 005b7240  ca 0f 86 61 cc 1b 7d 0a  0b 09 45 88 fc 06 fd ac  |...a..}...E.....|
 005b7250  f6 82 7e 5d 7d 13 5a 56  8c 14 fe 7f 55 bf 19 d4  |..~]}.ZV....U...|
 005b7260  ea 2d d7 00 56 45 52 53  0a                       |.-..VERS.|
 005b7269


A proper image should have a trailer similar to this:

 $ hexdump -C openwrt-initramfs.bin |tail -4
 005746d0  10 e1 d2 0c 73 0a ff 07  eb 12 c6 f1 0a eb ca 00  |....s...........|
 005746e0  56 45 52 53 0a 56 39 2e  39 39 28 41 41 5a 49 2e  |VERS.V9.99(AAZI.|
 005746f0  30 29 20 7c 20 30 36 2f  32 34 2f 32 30 32 31 0a  |0) | 06/24/2021.|
 00574700

The last one is the actual image I used to my initial install from OEM.
It worked.


Bjørn

 target/linux/realtek/image/Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/target/linux/realtek/image/Makefile b/target/linux/realtek/image/Makefile
index ebc0c0a78480..38b4d5e441cc 100644
--- a/target/linux/realtek/image/Makefile
+++ b/target/linux/realtek/image/Makefile
@@ -10,7 +10,7 @@ DEVICE_VARS += ZYXEL_VERS
 
 define Build/zyxel-vers
        ( echo VERS;\
-       for hw in $(1); do\
+       for hw in $(ZYXEL_VERS); do\
                echo -n "V9.99($$hw.0) | ";\
                date -d @$(SOURCE_DATE_EPOCH) +%m/%d/%Y;\
        done ) >> $@
@@ -117,7 +117,7 @@ define Device/zyxel_gs1900
   IMAGE_SIZE := 6976k
   DEVICE_VENDOR := ZyXEL
   UIMAGE_MAGIC := 0x83800000
-  KERNEL_INITRAMFS := kernel-bin | append-dtb | gzip | zyxel-vers $$$$(ZYXEL_VERS) | \
+  KERNEL_INITRAMFS := kernel-bin | append-dtb | gzip | zyxel-vers | \
 	uImage gzip
 endef
 
-- 
2.20.1