Which filesystem can live on one flash sector?

Which filesystem can live on one flash sector?

[fred]

Hi,

I am using CRAMFS plus RAMFS on my board.
And there is only one sector left for saving configuration data.
Can I put a file system, e.g. JFFS, on it?

BR,
Fred

Re: Which filesystem can live on one flash sector?

[Jörn Engel]

On Tue, 10 December 2002 14:02:05 +0800, fred wrote:
> 
> I am using CRAMFS plus RAMFS on my board.
> And there is only one sector left for saving configuration data.
> Can I put a file system, e.g. JFFS, on it?

You can use ext2 or minix. The just ain't no journaling with only one
erase block, so forget about jffs[12], ext3 and so on.

Jörn

-- 
My second remark is that our intellectual powers are rather geared to
master static relations and that our powers to visualize processes
evolving in time are relatively poorly developed.
-- Edsger W. Dijkstra

RE: Which filesystem can live on one flash sector?

[fred]

Ok, I understand I can't run JFFS at only one sector.

In fact, I have 64k space left for saving configuration data.
The size of a sector is 64k normally except the bottom sectors that are 8k,
4k, 4k, 16k, 32k.
So you see, I have five sectors to run JFFS rather than one 64k sector.
Then, is it possible to run JFFS on these sectors?

-----Original Message-----
From: Charles Manning [mailto:manningc2@actrix.gen.nz]
Sent: Tuesday, December 10, 2002 3:07 PM
To: fred@sc23.sc.mcel.mot.com
Subject: Re: Which filesystem can live on one flash sector?

On Tue, 10 Dec 2002 19:02, you wrote:
> Hi,
>
> I am using CRAMFS plus RAMFS on my board.
> And there is only one sector left for saving configuration data.
> Can I put a file system, e.g. JFFS, on it?


I don't see how any fs - alive or dead - could live in one sector. You need
at least one free sector to do garbage collection. (more for any real file
system).

Sounds to me like you'll just have to use it as raw flash.

-- Charles

Re: Which filesystem can live on one flash sector?

[Jörn Engel]

On Tue, 10 December 2002 21:56:31 +0800, fred wrote:
> 
> Ok, I understand I can't run JFFS at only one sector.
> 
> In fact, I have 64k space left for saving configuration data.
> The size of a sector is 64k normally except the bottom sectors that are 8k,
> 4k, 4k, 16k, 32k.
> So you see, I have five sectors to run JFFS rather than one 64k sector.
> Then, is it possible to run JFFS on these sectors?

Yes, jffs (not jffs2) would be working on those sectors. But I fear
that the partition code doesn't treat them seperately, so jffs will
only see one sector and won't work.
You should tweak the partition code or provide your own mapping driver
to get it working. Something like that

Jörn

-- 
Everything should be made as simple as possible, but not simpler.
-- Albert Einstein

Re: Which filesystem can live on one flash sector?

[Russ Dill]

On Mon, 2002-12-09 at 23:02, fred wrote:
> Hi,
> 
> I am using CRAMFS plus RAMFS on my board.
> And there is only one sector left for saving configuration data.
> Can I put a file system, e.g. JFFS, on it?

I'd make another block free and then do some sort of journalling from
userspace (each data block has a header with crc, size, header crc, and
revision). If you flash it boot block flash, the boot block may be the
place to find a couple small free sectors.