[U-Boot-Users] fdt_chosen()

[U-Boot-Users] fdt_chosen()

[Timur Tabi]

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.

-- 
Timur Tabi
Linux Kernel Developer @ Freescale

[U-Boot-Users] fdt_chosen()

[Timur Tabi]

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.

-- 
Timur Tabi
Linux Kernel Developer @ Freescale

[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