[PATCH v6 09/25] arm: xenguest_arm64: Add a fake devicetree file

[Simon Glass]

Hi François,

On Fri, 3 Dec 2021 at 10:03, François Ozog <francois.ozog at linaro.org> wrote:
>
>
>
> On Fri, 3 Dec 2021 at 17:04, Simon Glass <sjg at chromium.org> wrote:
>>
>> Hi Tom,
>>
>> On Fri, 3 Dec 2021 at 05:14, Tom Rini <trini at konsulko.com> wrote:
>> >
>> > On Thu, Dec 02, 2021 at 12:23:10PM -0700, Simon Glass wrote:
>> > > Hi François,
>> > >
>> > > On Thu, 2 Dec 2021 at 11:44, François Ozog <francois.ozog at linaro.org> wrote:
>> > > >
>> > > > Hi Simon
>> > > >
>> > > > On Thu, 2 Dec 2021 at 19:29, Simon Glass <sjg at chromium.org> wrote:
>> > > >>
>> > > >> Hi François,
>> > > >>
>> > > >> On Thu, 2 Dec 2021 at 11:17, François Ozog <francois.ozog at linaro.org> wrote:
>> > > >> >
>> > > >> > Hi Simon
>> > > >> >
>> > > >> > On Thu, 2 Dec 2021 at 19:05, Simon Glass <sjg at chromium.org> wrote:
>> > > >> >>
>> > > >> >> Hi Tom,
>> > > >> >>
>> > > >> >> On Thu, 2 Dec 2021 at 10:56, Tom Rini <trini at konsulko.com> wrote:
>> > > >> >> >
>> > > >> >> > On Thu, Dec 02, 2021 at 05:40:46PM +0000, Oleksandr Andrushchenko wrote:
>> > > >> >> > > Hi, Simon!
>> > > >> >> > >
>> > > >> >> > > Sorry for being late to the party
>> > > >> >> > >
>> > > >> >> > > On 02.12.21 17:59, Simon Glass wrote:
>> > > >> >> > > > Add an empty file to prevent build errors when building with
>> > > >> >> > > > CONFIG_OF_SEPARATE enabled.
>> > > >> >> > > >
>> > > >> >> > > > The build instructions in U-Boot do not provide enough detail to build a
>> > > >> >> > > > useful devicetree, unfortunately.
>> > > >> >> > > Xen guest doesn't use any built-in device trees as the guest's device tree is provided
>> > > >> >> > > by the Xen hypervisor itself and is generated at the virtual machine creation time: it is
>> > > >> >> > > populated with memory size, number of CPUs etc. based on [1].
>> > > >> >> > > So, even if we provide some device tree here it must not be used by U-boot at
>> > > >> >> > > the end of the day. Thus, it might be a reasonable solution to provide an empty device
>> > > >> >> > > tree as you do, but put a comment that it is not used.
>> > > >> >> >
>> > > >> >> > So another example of why this series is taking things in the wrong
>> > > >> >> > direction.
>> > > >> >>
>> > > >> >> Why?
>> > > >> >
>> > > >> > I only had that comment in mind: "there is none so deaf as he who will not hear."
>> > > >>
>> > > >> Hey, stop the pile-on. It's not useful.
>> > > >>
>> > > >> I've guided U-Boot's use of devicetree for 10 years successfully. The
>> > > >> current state is a mess and I just to straighten it out.
>> > > >>
>> > > > I admire your talent and knowledge.
>> > > > I know you are 99,99% of the time correct and spot on for your comments in many meetings we were attending.
>> > > > When you questioned a number of points I made, I first tried to understand what I got wrong because you said it.
>> > > > And you were right ;-)
>> > > > For this topic, I made every effort to come to your position, but definitively can't.
>> > >
>> > > Thank you. I think this will come together in a few years when
>> > > devicetree is sorted out in U-Boot and Binman is more widely used.
>> > >
>> > > For this series, if and when it is applied, I predict:
>> > > - it will not cause any confusion
>> > > - it will aid development
>> > > - it will help with discoverability, pressuring people to explain how
>> > > to build for their systems
>> > > - it will be a good basis for future work (we have a long list)
>> > > - everyone will wonder what the fuss was about
>> > >
>> > > Here is the commit that introduced OF_PRIOR_STAGE. It attracted no
>> > > such push-back.
>> > >
>> > > commit 894c3ad27fa940beb7fdc07d01dcfe81c03d0481
>> > > Author: Thomas Fitzsimmons <fitzsim at fitzsim.org>
>> > > Date:   Fri Jun 8 17:59:45 2018 -0400
>> > >
>> > >     board: arm: Add support for Broadcom BCM7445
>> > >
>> > >     Add support for loading U-Boot on the Broadcom 7445 SoC.  This port
>> > >     assumes Broadcom's BOLT bootloader is acting as the second stage
>> > >     bootloader, and U-Boot is acting as the third stage bootloader, loaded
>> > >     as an ELF program by BOLT.
>> > >
>> > >     Signed-off-by: Thomas Fitzsimmons <fitzsim at fitzsim.org>
>> > >     Cc: Stefan Roese <sr at denx.de>
>> > >     Cc: Tom Rini <trini at konsulko.com>
>> > >     Cc: Florian Fainelli <f.fainelli at gmail.com>
>> >
>> > I want to cycle back over here.  Yes, historically a number of things
>> > came in that perhaps shouldn't have.  I went with "well, this is what we
>> > need to handle this case I suppose" and applied it.
>>
>> Yes and we need to move things forward. We can't just object to things
>> without an alternative.
>
> As far as I can follow the threads, I proposed the dts to be empty to pass compilation and move forward, but I think you haven't replied. The empty dts can contain a comment pointing to documentation, which could describe the DT lifecycle of the platform, and a template dts that could be used for adventurous developers.

That does not go far enough for me. We actually do want to be able to
build U-Boot and run it on the board, e.g. in a lab. We cannot do that
if there are manual instructions involved. The onus needs to be on
contributors to make their boards actually buildable/bootable with
U-Boot.

[..]

REgards,
Simon