[PATCH 4/5] env: Add support for board specific special default environment

[Marek Behún]

On Thu, 28 Oct 2021 21:17:41 -0600
Simon Glass <sjg at chromium.org> wrote:

> Hi Marek,
> 
> On Wed, 27 Oct 2021 at 21:28, Marek Behún <kabel at kernel.org> wrote:
> >
> > From: Marek Behún <marek.behun at nic.cz>
> >
> > The default_environment[] buffer is built at compile time, but sometimes
> > it makes sense for some default environment variables to be determined
> > at runtime, for example:
> > - one board code may support different boards, and needs that
> >     fdtfile, board, board_name
> >   are set appropriately when command
> >     env default -a
> >   is executed
> > - some boards may want to prohibit the
> >     env default -a
> >   command to remove device MAC addresses stored in
> >     ethaddr, ethNaddr.
> >   This is the case for the ESPRESSObin board code, for example, where
> >   currently the board_late_init() function rewrites the default
> >   environment array to achieve this.
> >
> > Add a new board specific function,
> >
> >   const char *board_special_default_env(unsigned i, const char **name);
> >
> > which returns the value of i-th board special default environemnt
> > variable, while storing it's name to *name.
> >
> > Add default weak implementation of this functions returning NULL.
> >
> > Add code to default environemnt handlers in env/common.c, which iterate
> > these special board default environment variables and get it's values in
> > precedence to values in the default_environment[] buffer.
> >
> > Signed-off-by: Marek Behún <marek.behun at nic.cz>
> > ---
> >  env/common.c | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++--
> >  1 file changed, 96 insertions(+), 3 deletions(-)  
> 
> What do you think about using a sysinfo driver for this? There are
> already a lot of weak functions in U-Boot.

I confess I am looking at sysinfo API for the first time just now. It
seems like a reasonable thing, but how to combine with default
environment for this?

The thing is that Pali's code for ESPRESSObin needs to prohibit
deleting the ethaddrs from env with "env default -a", because there
were issues with the mac address being lost...

Marek