[RFC] Kbuild support for ARM FIT images

[Russell King - ARM Linux]

(Dropped uboot mailing list because it constantly holds my mails for
moderation.)

On Thu, Feb 21, 2013 at 09:08:58AM -0500, Tom Rini wrote:
> On 02/21/2013 08:46 AM, Russell King - ARM Linux wrote:
> > We're about to make it harder how?  By forcing them to use DT
> > blobs? Or by forcing them to have to use the combined zImage + DT
> > format because their boot loaders are soo broken that they can't
> > deal with multiple images?
> 
> None of that.  We're making it harder since most folks don't have a
> board with 'bootz' built-in and the 'uImage' target doesn't build now
> (unless, yes, you pass LOADADDR to make) so they either format it by
> hand (/ adjust their local scripting) or do what you're doing.

And adjusting their process to pass an additional argument to the
kernel make is too difficult?

So instead we have to change the kernel makefiles and scripting to
create yet another uboot specific format, which is going to need
them to edit their scripts in a much more invasive way _anyway_?

"or do what you're doing" - oh you mean, adding an additional column
to the database configuration, digging out from the kernel git
history what the load addresses should be, updating the database tables
with that, editing the build system scripts to extract this new column
from the database, and pass it into make... yes, complicated isn't it.
Didn't take long to sort out though, and didn't require a load of new
file formats to fix.

> > Yes, things have become a _little_ harder since OMAP has switched
> > to multiplatform, but it really isn't that bad.  My build and boot
> > test system still works, and it uses uImage for all the OMAP
> > platforms. You just have to give the right LOADADDR= argument to
> > the kernel to make the uImage generation work again.  Sure, the
> > resulting uImage can't be loaded at a different address, but you if
> > you need to change that, you can quite easily move the existing
> > uImage out and re-run make ARCH=arm uImage LOADADDR=<something
> > else> and hey presto, you end up with the uImage generated for a
> > different address.
> > 
> > But: we wouldn't be in this situation if it weren't for these
> > absurd uboot uImage formats in the first place.  Or even be needing
> > this FIT stuff if zImage was just used directly.
> 
> FIT isn't required.  FIT is just trying to offer a nice usability
> thing to folks.  A point of device trees is a single image works in a
> lot of places.  FIT gives you a single file works in a lot of places.

Well, FIT isn't everywhere either.  So really that argument doesn't
stand for the same reasons that bootz support isn't everywhere either.

My SDP4430's uboot provided by TI uses uboot 1.1.4.  Therefore, it
doesn't support FIT, nor bootz - only uImage.

> > uboot dug _itself_ into this hole.  It's uboot's problem.
> 
> A whole lot  of people dug this particular hole.  Joel is trying to
> offer up a solution that maybe makes things easier for everyone.  Or
> it gets rejected here too and distros will come up with their N
> different ways to try and provide easier experiences to the end user.

FIT just propagates the "boot loader specific file format" absurdity
which was a mistake when uImage came along...