JFFS2 internals question

JFFS2 internals question

["David Müller (ELSOFT AG)"]

Hello

As i'm not a JFFS2 guru i hope someone familar with the JFFS2 internals
could answer this question:

Situation:

JFFS2 filesystem on a NAND flash device:


Is it true that the read calls emitted from the JFFS2 code to the MTD HW
driver do not cross NAND block boundries (nand_read_ecc() has its start
and end point of reading in the same NAND block)?

TIA

Dave

Re: JFFS2 internals question

[David Woodhouse]

On Thu, 2003-08-14 at 12:42, "David Müller (ELSOFT AG)" wrote:
> Is it true that the read calls emitted from the JFFS2 code to the MTD HW
> driver do not cross NAND block boundries (nand_read_ecc() has its start
> and end point of reading in the same NAND block)?

I'd first like to know why you think you need the answer to this... :)

-- 
dwmw2

Re: JFFS2 internals question

["David Müller (ELSOFT AG)"]

David Woodhouse wrote:
> On Thu, 2003-08-14 at 12:42, "David Müller (ELSOFT AG)" wrote:
> 
>>Is it true that the read calls emitted from the JFFS2 code to the MTD HW
>>driver do not cross NAND block boundries (nand_read_ecc() has its start
>>and end point of reading in the same NAND block)?
> 
> 
> I'd first like to know why you think you need the answer to this... :)
> 

I need it to test a theory.


Dave

Re: JFFS2 internals question

[David Woodhouse]

On Thu, 2003-08-14 at 13:15, "David Müller (ELSOFT AG)" wrote:
> David Woodhouse wrote:
> > On Thu, 2003-08-14 at 12:42, "David Müller (ELSOFT AG)" wrote:
> > 
> >>Is it true that the read calls emitted from the JFFS2 code to the MTD HW
> >>driver do not cross NAND block boundries (nand_read_ecc() has its start
> >>and end point of reading in the same NAND block)?
> > 
> > 
> > I'd first like to know why you think you need the answer to this... :)
> > 
> 
> I need it to test a theory.

I think we do make read calls which cross a page boundary, yes.

-- 
dwmw2

Re: JFFS2 internals question

[jasmine]

David wrote:

> I think we do make read calls which cross a page boundary, yes.

And the inability to handle such calls was the reason that the
old DiskOnChip driver didn't work with jffs2, as I recall.

-Jasmine.

Re: JFFS2 internals question

["David Müller (ELSOFT AG)"]

David Woodhouse wrote:
> On Thu, 2003-08-14 at 13:15, "David Müller (ELSOFT AG)" wrote:
> 
>>David Woodhouse wrote:
>>
>>>On Thu, 2003-08-14 at 12:42, "David Müller (ELSOFT AG)" wrote:
>>>
>>>
>>>>Is it true that the read calls emitted from the JFFS2 code to the MTD HW
>>>>driver do not cross NAND block boundries (nand_read_ecc() has its start
>>>>and end point of reading in the same NAND block)?
>>>
>>>
>>>I'd first like to know why you think you need the answer to this... :)
>>>
>>
>>I need it to test a theory.
> 
> 
> I think we do make read calls which cross a page boundary, yes.
> 

Sorry, i was talking about block boundary, not page boundary. Or is it
just a typo?


Dave

Re: JFFS2 internals question

[David Woodhouse]

On Thu, 2003-08-14 at 13:35, "David Müller (ELSOFT AG)" wrote:
> Sorry, i was talking about block boundary, not page boundary. Or is it
> just a typo?

Oh, sorry. We'll not read over _logical_ eraseblock boundaries but on
large chips we may artificially increase the eraseblock size to be 2* or
4* the physical eraseblock size, to reduce the number of 'struct
jffs2_eraseblock' we have to allocate. In that case, yes, we'll be
reading across eraseblock boundaries.

-- 
dwmw2