[U-Boot-Users] Dynamic location of the environment sector

Angelos Manousarides amanous at inaccessnetworks.com
Wed Jun 21 19:16:58 CEST 2006

Wolfgang Denk wrote:
> In message <20060621104820.GA23461 at inaccessnetworks.com> you wrote:
>>Indeed it does not. The problem however, just for the record is code
>>like the following segment:
>>#  define ENV_IS_EMBEDDED       1
>># endif
> This is not a real problem, me thinks.
>>The preprocessor cannot obviously perform checks and do arithmetic with
>>C variables and constructs:
>>include/environment.h:64:20: token "[" is not validin preprocessor expressions
> Well, don't use '[' in your definitions, then :-)

Ok I finally decided to switch to an embedded environment in the text 
segment of u-boot. The documentation says it is tricky business, but I 
prefer to take that risk and have a single image for all the platforms, 
without wasting 512K of flash space.

The placement of the environment is a bit of a tricky business though in 
the ARM platform. Initially I tried to place it on the end of the sector 
but realised that after the text segment is the data segment of which 
the size I don't know. The other solution is to place it at the 
beginning right after the reset code, but this also does not have a 
fixed size (cpu/pxa/start.o). I decided to use the latter approach and 
place the environment at the 16K boundary, hoping that the object 
start.o will never reach this size.

Another problem I encountered has to do with the manipulation of the 
environment with the "saveenv" command. The image I produced was ok, I 
booted and the default environment was recognized. I saw that the file 
common/environment.c defines before the environment the env_size 
variable, therefore placing the environment at 0x4004 than 0x4000 that 
is my hard coded offset. This causes a problem with the saveenv command, 
since here (common/env_flash.c):

/* static env_t *flash_addr = (env_t *)(&environment[0]);-broken on 
static env_t *flash_addr = (env_t *)(CFG_ENV_ADDR + sizeof(unsigned long));

the address the command uses is the initial offset (0x4000) and not the 
actual offset after the env_size variable.

Is this a bug introduced by the workaround for the flash_addr? Or am I 
doing something wrong and the env_size variable should never have 
appeared in my code?


Angelos Manousaridis

More information about the U-Boot mailing list