[U-Boot-Users] Question about CFG_ENV_ADDR during RAMBOOT

Wolfgang Denk wd at denx.de
Thu May 24 15:03:39 CEST 2007

Dear Ladislav,

in message <20070524121048.GA6516 at michl.2n.cz> you wrote:
> And this is another very interesting thread:
> Subject: [PATCH] DataFlash for AT91RM9200DK board
> http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/9175
> It contains quite interesting part which is worth to repeat there
> (by Wolfgang Denk, 2003-06-04)

I don't have words to express how much I repent these words.

When I wrote this, I had no  idea  what  DataFlash  is  and  that  it
actually uses a serial interface. It would be lame if I tried to come
up ith the "little time" excuse, because it does not help to undo the
damage done then.

> > In our case, we use it to store and boot an image of linux(the dataflash
> > contains the linux zImage and the ramdisk).
> > This dataflash can be used also for a filesystem.
> In this case I think we should offer an interface which looks\
> to the user like mmeory.

This was  a  major  misapprehension,  and  I  formally  apologize  to
everybody who suffered or still suffers from the consequences.

> That makes clear reasons behind Ulf's statement and also shows that not
> all decisions are good ones.

Right. This was definitely a bad one.

> If anyone feels need to fix u-boot's dataflash support, then please
> either lets continue in more than 16 weeks old debate in 'Atmel
> DataFlash hooks' thread or spawn new one.

DataFlash is much more similar to NAND flash than it is to NOR flash
or RAM. 

IMHO a pretty good summary of the last state of the previous thread
can be found here:


In short:

* the cmd_mem hooks should be removed and replaced by a new interface
* the new interface will probably be similar to the NAND interface
* both the process for the migration and the new command format
  need to be discussed
* there is no intention to remove functionality, nor to sabotage
  anybody, but there is pending cleanup that needs to get done sooner
  or later

During the transition perion, it is IMHO not a good idea to add more
code to the old interface because this will just increase the amount
of cleanup work that will be needed later; instead, efforts should be
put in helping to define, implement and test the new interface.


Wolfgang Denk

DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
"The algorithm to do that is extremely nasty. You might want  to  mug
someone with it."                   - M. Devine, Computer Science 340

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