[openwrt/openwrt] ath79/mikrotik: disable building NAND images

[LEDE Commits]

adrian pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/9d96b6fb720d9cecc7bd50b4f16dabe1b337f9f2

commit 9d96b6fb720d9cecc7bd50b4f16dabe1b337f9f2
Author: Adrian Schmutzler <freifunk at adrianschmutzler.de>
AuthorDate: Sun Dec 27 20:33:57 2020 +0100

    ath79/mikrotik: disable building NAND images
    
    The current support for MikroTik NAND-based devices relies on a
    gross hack that packs the kernel into a static YAFFS stub, as the
    stock bootloader only supports booting a YAFFS-encapsulated kernel.
    
    The problem with this approach is that since the kernel partition is
    blindly overwritten without any kind of wear or badblock management
    (due to lack of proper support for YAFFS in OpenWRT), the NAND flash
    is not worn uniformly and eventually badblocks appear, leading to
    unbootable devices.
    
    This issue has been reported here [1] and discussed in more detail
    here [2].
    
    [1] https://forum.openwrt.org/t/rb433-bad-sector-cannot-start-openwrt/71519
    [2] https://github.com/openwrt/openwrt/pull/3026#issuecomment-673597461
    
    Until a proper fix is found (or the stock bootloader supports other
    filesystems), we disable building these images to prevent unknowing
    users from risking their devices.
    
    Thanks to Thibaut Varène for summarizing the details above.
    
    Signed-off-by: Adrian Schmutzler <freifunk at adrianschmutzler.de>
---
 target/linux/ath79/image/common-mikrotik.mk | 1 +
 1 file changed, 1 insertion(+)

diff --git a/target/linux/ath79/image/common-mikrotik.mk b/target/linux/ath79/image/common-mikrotik.mk
index b0c3feda20..6e739f2d85 100644
--- a/target/linux/ath79/image/common-mikrotik.mk
+++ b/target/linux/ath79/image/common-mikrotik.mk
@@ -17,4 +17,5 @@ define Device/mikrotik_nand
   IMAGE/sysupgrade.bin = append-kernel | kernel2minor -s 2048 -e -c | \
 	sysupgrade-tar kernel=$$$$@ | append-metadata
   DEVICE_PACKAGES := nand-utils
+  DEFAULT := n
 endef