[LEDE-DEV] Older u-boot mangles UBI from ubinize 1.5.2

[Richard Weinberger]

Hi!

On Thu, Aug 11, 2016 at 4:26 AM, J Mo <jmomo at jmomo.net> wrote:
> I tried re-flashing my UBI and tftpbooting my kernel before u-boot could
> ever get a chance to mangle it, and now I get much further, though I'm still
> not able to mount my rootfs for unknown reasons:
>
>     [    3.772502] ubi0: attaching mtd11
>     [    3.826477] UBI: EOF marker found, PEBs from 40 will be erased

WTF is this?
Reading the corresponding patch makes me very sad.

>     [    3.826638] ubi0: scanning is finished
>     [    3.872936] ubi0: volume 2 ("rootfs_data") re-sized from 9 to 430
> LEBs
>     [    3.873734] ubi0: attached mtd11 (name "rootfs", size 64 MiB)
>     [    3.878347] ubi0: PEB size: 131072 bytes (128 KiB), LEB size: 126976
> bytes
>     [    3.884234] ubi0: min./max. I/O unit sizes: 2048/2048, sub-page size
> 2048
>     [    3.890936] ubi0: VID header offset: 2048 (aligned 2048), data
> offset: 4096
>     [    3.897849] ubi0: good PEBs: 512, bad PEBs: 0, corrupted PEBs: 0
>     [    3.904627] ubi0: user volume: 3, internal volumes: 1, max. volumes
> count: 128
>     [    3.910815] ubi0: max/mean erase counter: 1/0, WL threshold: 4096,
> image sequence number: 2142265782
>     [    3.917902] ubi0: available PEBs: 0, total reserved PEBs: 512, PEBs
> reserved for bad PEB handling: 40
>     [    3.927275] ubi0: background thread "ubi_bgt0d" started, PID 54
>     [    3.937007] block ubiblock0_1: created from ubi0:1(rootfs)
>     [    3.942096] hctosys: unable to open rtc device (rtc0)
>     [    3.956528] VFS: Cannot open root device "ubi0:rootfs" or
> unknown-block(31,11): error -2
>     [    3.956556] Please append a correct "root=" boot option; here are the
> available partitions:
>
>
>
> Any advice on this? Any background information that I can read up on? My
> google searches have not come up with much. Ram knew about this, but I don't
> know if it's otherwise a known issue.
>
> The process works fine on the OEM system, so I assume this is some ubinize
> format change which is incompatible with the older u-boot. Or, the newer
> kernel code doesn't know how to deal with the UBI once the older u-boot has
> mangled/attached it.
>
> Seems like a backwards incompatibility issue.

Since OpenWRT/LEDE folks did more or less a hard fork of UBI I'm
ignoring this issue.
If you encounter something like that using vanilla UBI I'm all ears.

That said, I kind of understand that you, OpenWRT/LEDE, have a pile of
patches for auto probing rootfs
and other runtime stuff but touching the UBI on-flash format is beyond funny.
Doing so opens a can of worms and is painful for all parties. There
are customers which build their
products using OpenWrt and when they change the kernel at some point
it will get nasty.

This situation needs to be improved now. I invite you to discuss this
changes here on linux-mtd.
Especially the stuff where you change the on-flash format.
If UBI, or MTD in general, can do a better job in some areas, please
tell such that a decent solution can be found.
But your ad-hoc hacks need to stop.

-- 
Thanks,
//richard