[OpenWrt-Devel] [PATCH 1/2] imx6: bootscript: enable UBI fastmap support

[Richard Weinberger]

Koen,

----- Ursprüngliche Mail -----
>> +	# enable UBI fastmap support
>> +	setenv bootargs "${bootargs} ubi.fm_autoconvert=1"
>>   else
>>   	echo "Booting from block device ${bootdev}..."
>>   	setenv fsload "${fs}load ${dtype} ${disk}:1"
> 
> Hi Tim,
> 
> Shouldn't this patch also enable the required kernel symbol?
> (MTD_UBI_FASTMAP)
> 
> Next to that, even in kernel 4.19 I'm reading following regarding this
> feature:
> 
> Important: this feature is experimental so far and the on-flash │
> format for fastmap may change in the next kernel versions
> 
> 
> Hi Richard,
> 
> Apologies for dragging you in here.
> 
> How stable is this fastmap format?
> 
> Will it leave Experimental state in the near future?

Well, the format itself is stable. We never had a bug which required
such a change. So I guess we can consider it as stable.

So yes, it is high noon to remove the scary "experimental word" from
the Kconfig description. :)

That said, I suggest enabling Fastmap only if attach/boot time is
more important than NAND lifetime.
The downside of Fastmap is that it will wear out the first 64 blocks
of your NAND faster than other blocks and not doing a full scan
upon bootup might hide NAND problems which can cause trouble
when it is already too late.

Thanks,
//richard

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