On Wed, Mar 24, 2021 at 05:59:59PM +0100, Christophe Leroy wrote:

quoted

I think my changes maintain most of this due to the override of
CONFIG_CMDLINE_PREPEND. This is an upgrade and the inflexibility in powerpc is
an example of why these changes were created in the first place.

"inflexibility in powerpc" : Can you elaborate ?

 
the prom environment.

quoted

For example , say the default command line is "root=/dev/issblk0" from iss476
platform. And the bootloader adds "root=/dev/sda1"

The result is <prepend><bootloader><append>.

I'm still having hard time understanding the benefit of having both <prepend> and <append>.
Could you please provide a complete exemple from real life, ie what exactly
the problem is and what it solves ?

 
Say the boot loader of an old product is released with a command line of
"root=/dev/sda" and per the needs of the company or product the boot loader can
not be upgraded to change this command line. To change this behavior you would
need append or EXTEND.

Below I detail an example of PREPEND due to your list question.

quoted

Then you have,

root=/dev/issblk0 root=/dev/sda1

and the bootloader has precedent over the default command line. So root= in the
above cases is defined by the bootloader.

A person could input a command line into a boot loader, and it would override
the PREPEND values.

Can you imagine you have a default command line which makes root=/dev/issblk0 ,
but that doesn't work for you testing purpose. So you input into the boot loader
root=/dev/sda1 , since you have the default input in the bootloader OVERRIDEABLE
you can do this without re-compiling and just input the single root= command
into the bootloader.

Daniel