linux-kernel - Re: Compact Flash Question

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Date:	Tue, 6 May 2008 23:09:54 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	"Yigal Sadgat" <YSadgat1@...e.com>
Cc:	<linux-kernel@...r.kernel.org>, <linux-ide@...r.kernel.org>,
	<jwboyer@...ux.vnet.ibm.com>, <joern@...fs.org>
Subject: Re: Compact Flash Question

> (1) Can you really ignore bit(2) (CORR) in the Status register offset 7 that 
> tells
> you that the CF has detected and corrected a soft error?, etc.

I guess it might be interesting to log the error rate but we don't
currently do that. A corrected error is just that however - corrected by
the card itself.

> (2) An engineer at SanDisk Engineering told me NOT to do wear leveling.
> The file allocation table is written very frequently back into the flash. So
> is it really safe to assume that I don't need wear leveling???

Depends on your hardware vendor. Wear management is done within the CF
card and only the hardware vendor can tell you what they do. 

> (3) Re. the BUSY bit in the status register (offset 7, bit D7), anybody 
> experienced
> time outs?

Yes - both from failing CF cards and also other random events (bad
connections, people removing live cards etc)

> (4) Re Error register (offset 1) bit D7 (BBK), again, I was told that it 
> cannot (???)
> happen since the CF performs read-after-write and it automatically switches 
> good blocks
> for bad ones... Is this correct?

Depends on your hardware vendor. It certainly *can* occur with some CF
cards perhaps when they run out of spare blocks.

Alan
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