[U-Boot-Users] Warning for mpc8360emds users: fdt-cmd from u-boot-fdt.git

Jerry Van Baren gerald.vanbaren at smiths-aerospace.com
Thu Apr 5 20:12:58 CEST 2007

Bruce_Leonard at selinc.com wrote:
> Hi all
> u-boot-users-bounces at lists.sourceforge.net wrote on 04/05/2007 04:00:15 
> AM:
>> Wolfgang Denk wrote:
>>> In message <46146842.8060509 at gmail.com> you wrote:
>>>> If bootm edits/augments the FDT, the boot scripts/user has no chance 
> to 
>>>> change the items it edits/augments (biggie: the chosen node), or even 
>>>> print it before linux is launched.  This defeats 90% of the purpose 
> of 
>>>> the fdt command - allowing the user/script customize the blob before 
>>>> linux is launched.
>>> I agree that it should be *possible* to do this, if wanted.Similar
>>> like we can set up our own contents of thebootargs variable.
>>> On the other hand, bootm should do everything that is necessary to
>>> start a kernel without such interaction, if needed.
> <snip snip>
> My two cents worth (for what it's worth :-/): from the standpoint of 
> someone using uboot for the first time and having to learn from the ground 
> up without the benefit of having used this stuff for many years, I agree 
> with Wolfgang.  It took me two weeks just to figure out what a device tree 
> is and that I even needed one.  It took me two more days to figure out how 
> to create the blob and how to use it.  I still don't know the details of 
> DTS files, what needs to be in them or what the different fields mean. 
> Adding another step/level of obscurity with REQUIRING the use of fdt 
> commands and/or scripts is just another barrier to new users.  And I have 
> to tell you, this thing is a bear to learn.  For folks who have been 
> digging around in the guts of it, I'm sure it's trivial.  But I at least 
> am pretty overwhelmed by it.
> I think it would be great to have the option of using the ftd commands if 
> it suited your purpose, but still be able to use things as they currently 
> are.  That would be the most flexible, give the expert users something 
> they want, and not add yet another thing that new people HAVE to learn 
> just to get an OS to boot.
> Again just my 2 cents.  Flames welcome.
> Bruce

Yes, but now you are worth 5 figures more: expect a $00,000 raise as 
part of your next performance appraisal.

I plan to implement Andy Fleming's suggestion which will resolve the issue:
 > > What if we made it so if there isn't a chosen node in the blob when
 > > bootm is called, it fills in a default one.  This prevents some odd
 > > failures, and allows people to continue using device trees in the
 > > current manner, while still enabling the extra flexibility.

Pedantic Script: device trees and blobs are kernel things, they ain't 
our fault. :-P Yet. ;-)

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