Re: [microblaze-uclinux] JFFS2 and MTD

[Robert Swindells <rjs@fdy2.demon.co.uk>]

John Williams wrote:
>Robert Swindells wrote:
>> 
>>>I haven't - I saw that the output of mkfs.jffs2 when run on an empty 
>>>directory was itself empty, so just figured I could mount straight on 
>>>top of an empty mtdblock device.
>> 
>> Had you erased the area ?

>Yes -
>$ eraseall /dev/mtd6
>$ mount -t jffs2 /dev/mtd6 /var

>It is silent, no errors reported, but then the behaviour on trying to 
>create files etc.

I would erase it before trying to boot if you can.

There are also extra compile time debugging options that can be turned
on for JFFS2.

>>>Also another thing that's probably related that I'm unsure about, when 
>>>my board boots the JFFS2 driver is trying very hard to do something - I 
>>>get a bunch of messages like this:
>>>
>> 
>> The offsets look as if JFFS2 is using the wrong blocksize.

>should the jffs2 block size be related to some physical parameter of the 
>system?  What is the importance?

The JFFS2 block size is the flash block size. It needs to know this in
order to do wear levelling and to garbage collect dirty blocks.

>>>Is JFFS2 trying to mount some kind of default fdile system?  This is all 
>>>happening before the shell starts, and before I can do any explicit 
>>>mount -t jffs2 commands.
>> 
>> 
>> It isn't trying to mount anything at this stage, it will just format
>> up any blocks that are not marked as being already used. This works
>> best if the unused blocks are cleared.

>Sure - but how does the jffs2 module initialisation know which of the 
>flash partitions are available for use?  e.g. the mtd5 (image) segment 
>is not for jffs2, it is a raw kernel / filesys image.  I don't want 
>jffs2 playing anywhere near it.

Can you grab the boot messages just before setting up JFFS2 ?

>Should I be writing a partition table somewhere?

No, you only need one if you don't want to hard code partition sizes
into the kernel.

Robert Swindells
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