[U-Boot] "Embedding" default script with uboot image

[Przemyslaw Marczak <p.marczak@samsung.com>]

Hi,

On 09/30/2015 10:06 AM, Zatkovsk? Du?an wrote:
> Really nobody?
>
> --
> Dusan
>
> D?a 22. 9. 2015 o 14:20 Zatkovsk? Du?an nap?sal(a):
>> Hi all,
>>
>> Excuse my question if it was solved somewhere in forum, but I didn't
>> found an answer yet (maybe I can't find the right keywords).
>>
>> I am building the uboot with yocto for imx6 board. I have started with
>> some freescale defaults,
>> edited environment for my needs, saved environment etc ... Now I want
>> to create a custom
>> "default" boot script, that will do some "heurestics", such as "look
>> if usb stick is present, then boot from it, else boot from emmc, etc...".
>> Currently I am storing that script on first partition on emmc and
>> loading it with ext2load.
>>
>> But it has drawbacks:
>> - user should delete that file -> brick
>> - user should broke entire filesystem -> brick
>>
>> I want this script to be "embedded" somehow with uboot image (which is
>> placed outside partition table on device), but I didn't found any doc
>> how to do that.
>> Currently I use CONFIG_EXTRA_ENV_SETTINGS for some basic stuffbut it
>> is unmaintainable for bigger scripts.
>>
>> Any suggestions?
>>
>> Thank you.
>> --
>> Dusan
>>
>
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The ELCE is coming, so probably people are busy.

Please check those few suggestions, which can help you:
- you can "cat" the binaries of U-Boot and your script into one binary
- you can get the address of your script in the code with few lines:

unsigned long *ptr = (unsigned long *)&_end; - start address of your DTB

ptr += fdt_totalsize(ptr) >> 2; - start address of your script

- you can add some header with "magic code" before your script binary

- check the size limit of your u-boot binary, because your script can be 
broken if the output binary exceeds the size, which can be loaded to RAM 
by SPL.

- also check if your bigger binary will not overwrite something on the 
flash layout

- to execute the script at every boot, you can modify same late 
function, like autoboot_command in common/autoboot.c ?

- so at this point, you can check your script's magic code - if added

- run script with:

char cmd[64];

sprintf(cmd, "source %p", ptr);
run_command(cmd, 0);

If you add some logic for checking if the script is valid (e.g. header 
with size and crc ?), then I think you can be sure, that it will work.

Best regards,
-- 
Przemyslaw Marczak
Samsung R&D Institute Poland
Samsung Electronics
p.marczak at samsung.com