Re: [RFC 12/13] ARM: dts: ti: add dra71-evm FIT description file

[Rob Herring <robh@kernel.org>]

On Mon, May 21, 2018 at 09:57:54AM +0300, Tero Kristo wrote:
> On 17/04/18 17:49, Tony Lindgren wrote:
> > * Tero Kristo <t-kristo@ti.com> [180417 09:36]:
> > > In typical setup, you can boot a large number of different configs via:
> > > 
> > > bootm 0x82000000#dra71-evm#nand#lcd-auo-g101evn01.0
> > > 
> > > ... assuming the configs were named like that, and assuming they would be
> > > compatible with each other. The am57xx-evm example provided is better, as
> > > you can chain the different cameras to the available evm configs.
> > 
> > Why not just do it in the bootloader to put together the dtb?
> > 
> > Then for external devices, you could just pass info on the
> > kernel cmdline with lcd=foo camera=bar if they cannot be
> > detected over I2C.
> 
> (Added Linux ARM list to CC, this was not part of the original delivery.)
> 
> Ok trying to resurrect this thread a bit. Is there any kind of consensus how
> things like this should be handled? Should we add the DT overlay files to
> kernel tree or not?

IMO, yes.

> Should we add any kind of build infra to kernel tree, and at what level
> would this be? Just DT overlay file building support, and drop the FIT build
> support as was proposed in this RFC series or...?

I think I mentioned this already, but I expect that this is going to 
cause a number of conversions of dtsi + dtsi -> dtb into base dts and 
overlay(s) dts files. In doing so, we still need to be able to build the 
original, full dtb.

> U-boot can obviously parse the base DTB + overlay DTB:s into a single DTB,
> but this is somewhat clumsy approach and is relatively error prone to get it
> right.

Why? How is the kernel better?

> Building the FIT image post kernel build would also be possible, but who
> would be doing this, is there any need to get this done in generic manner or
> shall we just add SoC vendor specific tools for this?

I'll tell you up front, I'm not a fan of FIT image (nor uImage, 
Android boot image, $bootloader image). If you want a collection of 
files and some configuration data, use a filesystem and a text file.

Rob