On Fri, 23 May 2014 07:41:30 +0100
Ian Campbell <[email protected]> wrote:

> On Fri, 2014-05-23 at 06:44 +0800, Andy Green wrote:
> > On 22 May 2014 22:49, Ian Campbell <[email protected]> wrote:
> > > On Thu, 2014-05-22 at 20:52 +0800, Andy Green wrote:
> > >> On 22 May 2014 17:50, Ian Campbell <[email protected]> wrote:
> > >> > On Wed, 2014-05-21 at 14:39 +0300, Riku Voipio wrote:
> > >> >>
> > >> >> Hi,
> > >> >>
> > >> >> I've collected a list of where people install their dtb files
> > >> >> these days;
> > >> >>
> > >> >> https://wiki.linaro.org/Platform/DeviceTreeConsolidation
> > >> >>
> > >> >>
> > >> >> Every distribution has a slightly different variation of
> > >> >> install location, which is not good - we can't tell end users
> > >> >> that "this is the place you can expect to find your device
> > >> >> tree files regardless of what distribution you choose".  Some
> > >> >> questions I have here before we proceed discussing what would
> > >> >> be the standardized location:
> > >> >>
> > >> >>
> > >> >> 1) Anything missing of the pros and cons of different
> > >> >> locations?
> > >> >
> > >> > FWIW Debian will now arrange for the correct DTB for the
> > >> > platform to be installed as /boot/dtb-$(uname -r) as well as
> > >> > the /usr/lib location.
> > >> ...
> > >> > I'm more or less ambivalent about installing all of the
> > >> > possible DTB files in a similar location though. I'm not sure
> > >> > what the use case for that is. Wouldn't you also need to
> > >> > standardise on the dtb filename for each platform and
> > >> > effectively make that ABI?
> > >>
> > >> For installs on eg, an SD Card, there's nothing stopping the one
> > >> SD Card being usable on multiple different SoC platforms if the
> > >> bootloader will allow it.
> > >
> > >> For example Fujitsu have various SoC with bootloader in HSSPI
> > >> NOR, which knows the right dtb filename for that SoC.
> > >>
> > >> So if all the dtbs are in /boot/whatever, that same SD Card is
> > >> capable to boot on any of them, since they're all supported by
> > >> the same single kernel binary from the same SD Card, and the
> > >> bootloader picked out the right one for what it happens to be
> > >> running on.  It's very convenient.
> > >
> > > But such an sd card would only work on these Fujitsu SoCs,
> > > wouldn't it?
> > 
> > No... if you consider "multi_v7_defconfig" in mainline that one
> > kernel binary is supporting
> 
> I know this.
> 
> What I meant was that the boot script on the sd card would be assuming
> that the bootloader was the Fujitsu one which "knows the right dtb
> filename for that SoC", and hence would only work on those systems.
> Unless this knowledge of the right dtb name is to become a standard
> also...

no it should be ingrained in u-boot and ideally people use
extlinux.conf but if they use boot.scr they make sure and call into
u-boots variables for memory locations and dtb file names


> > > In which case a single boot.scr could equally well handle it.
> > ...
> > > Or is there a separate effort to standardise uboot bootcmd
> > > settings as well?
> > 
> > As Stephen says, a few weeks ago I installed Fedora 20 on a
> > Cubiebrick for my own web services, I noticed there is a monster
> > U-Boot script coming with Fedora now that is trying to normalize
> > U-Boot across all the boards (a pretty amazing endeavour actually).
> 
> ... which it sounds like it might be.
> 
> How do other OSes call their DTB files? I expect they aren't
> consistent with Linux...
> 
> Ian.
> 
> 
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