linux-kernel - Re: [PATCH] UBI: add minimal amount of reserved erase blocks in Kconfig

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Message-ID: <CACQ1gAgGbYvTO=_vVW11Ru9OXpra7oiJinbpX=DBiOHmoUtA8g@mail.gmail.com>
Date:	Fri, 29 Jun 2012 09:17:11 +0200
From:	Richard Genoud <richard.genoud@...il.com>
To:	dedekind1@...il.com
Cc:	David Woodhouse <dwmw2@...radead.org>,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Shmulik Ladkani <shmulik.ladkani@...il.com>
Subject: Re: [PATCH] UBI: add minimal amount of reserved erase blocks in Kconfig

2012/6/28 Artem Bityutskiy <dedekind1@...il.com>:
> On Thu, 2012-06-28 at 18:07 +0200, Richard Genoud wrote:
>> Agreed, it seems that 2% of the whole flash (at least for SLC device)
>> is more realistic.
>
> Agree, feel free to send a separate patch for this.
Done !
>
>> > Frankly, I do not understand this logic :-) And your patch looks wrong -
>> > it touches the "auto-format" code which you may consider more like a
>> > "debugging" feature and should not rely on this in production.
>> Sorry, but I don't understand what you mean by the "auto-format" code.
>
> Yeah, right, this comment was incorrect, sorry.
>

I was thinking that instead of giving to ubiattach the MBB, we could
give it the MBB percentage (maximum bad blocks percentage of the whole
flash device).
>From this % and the whole flash size, we get the MBB number, and set
beb_rsvd_level for each MTD part.
It will be easier for userspace, as we won't have to set a different
value for different flash size. The default 2% value will (almost)
always be correct.
We can even get rid of the CONFIG_MTD_UBI_BEB_RESERVE option.

BTW, the real killer feature would be that the flash gives its NVB or
MBB value in response to the READ_ID command, but unfortunately that's
not the case...
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