[U-Boot-Users] fdt_chosen()

[Jerry Van Baren]

Timur Tabi wrote:
> Jerry,
> 
> I noticed that fdt_chosen() is called with force=0.  Does that mean that 
> if the DTB has a chosen node in it already, that it won't be 
> overwritten?  If so, I think that's wrong, because some DTBs have a 
> bogus chosen section in them that has, in the past, always been 
> overwritten by U-Boot.  If the chosen node already exists, then it means 
> that it was present in the DTS when it was compiled, and that means the 
> DTS is probably old and the chosen node has bad data in it.

Hi Timur,

In the "old" code, if the dts had a "chosen" node bootm created _a 
second_ "chosen" node which is just wrong.

I originally removed the auto-generation of the "chosen" node which 
forced the user to use the "fdt chosen" command (manually or as a boot 
script) to create the node if he really wanted it (and it would add 
missing properties and overwrite existing properties the "chosen" node, 
rather than creating a bogus node).

Forcing the user to create the "chosen" node (either manually/scripted 
or through the dts) was deemed undesirable.  In the discussion that 
ensued, at least as I understood it, the compromise was to create the 
node if it did not exist and not touch it if it did exist.
   <http://article.gmane.org/gmane.comp.boot-loaders.u-boot/27553>

The reason I chose to /not/ create/overwrite "chosen" properties as part 
of the bootm command is that would potentially overwrite changes that 
the user made before running bootm.  Scenario:
fdt addr <address>
fdt chosen # create the default chosen node and properties
fdt set /chosen <someprop> <somevalue>
bootm  # ...would be BAD if <someprop> were rewritten

I'm open to tuning the behavior, but I don't like automagic and I *hate* 
automagic which it undoes something I just got done doing.

Best regards,
gvb