Hi Tom,
On Fri, 8 Sept 2023 at 17:54, Tom Rini trini@konsulko.com wrote:
On Fri, Sep 08, 2023 at 01:13:42PM +0300, Ilias Apalodimas wrote:
Hi Simon,
On Thu, 7 Sept 2023 at 15:23, Simon Glass sjg@chromium.org wrote:
Hi Ilias,
On Wed, 6 Sept 2023 at 23:20, Ilias Apalodimas ilias.apalodimas@linaro.org wrote:
Hi Rob,
[...]
> > > > > > > > What is the point of removing them? Instead, we should make sure that > > > > we upstream the bindings and encourage SoC vendors to sync them. If we > > > > remove them, no one will bother and U-Boot just becomes a dumping > > > > ground. > > > > > > Well things like the binman entries in DT are U-Boot specific and not > > > useful for HW related descriptions or for Linux or another OS being > > > able to deal with HW so arguably we're already a dumping ground to > > > some degree for not defining hardware. > > > > I have started the process to upstream the binman bindings. > > I don't think they should be in DT at all, they don't describe > anything to do with hardware, or generally even the runtime of a > device, they don't even describe the boot/runtime state of the > firmware, they describe build time, so I don't see what that has to do > with device tree? Can you explain that? To me those sorts of things > should live in a build time style config file.
For the record, I tend to agree.
+1
I beg to differ. Devicetree is more than just hardware and always has been. See, for example the /chosen and /options nodes.
There are exceptions...
We've been this over and over again and frankly it gets a bit annoying. It's called *DEVICE* tree for a reason. As Rob pointed out there are exceptions, but those made a lot of sense. Having arbitrary internal ABI stuff of various projects in the schema just defeats the definition of a spec.
Our efforts should not just be about internal ABI, but working to provide a consistent configuration system for all firmware elements.
And that's what the firmware handoff was all about. I get what you are trying to do here. I am just aware of any other
"just not aware" did you mean?
Yep, sorry!
project apart from U-Boot which uses DT for it's own configuration. So trying to standardize some bindings that are useful to all projects that use DT is fine. Trying to *enforce* them to use it for config isn't IMHO.
We cannot have it both ways, i.e. refusing to accept non-hardware bindings and then complaining that U-Boot does not pass schema validation. Devicetree should be a shared resource, not just for the use of Linux.
It's not for the use of Linux, I've wasted enough time repeating that and so has Rob. Please go back to previous emails and read the arguments.
Right, it's not just for Linux, but Linux is where most of the exceptions to the "ONLY HARDWARE" rule got in, because they also make sense.
Exactly.
And the overarching point Simon keeps trying to make I believe can be boiled down to that too. There are things that one does not have a (reasonable) choice about how to do things with when interacting with the hunk of melted sand on your desk and that information needs to go somewhere.
DT is a big hammer indeed, but that doesn't mean we always need to use it. I never disagreed with adding nodes that make sense and will be useful for others. For example, the internal Driver model configuration options used to enable a device early etc etc are probably useful to more projects. On the other hand, if U-Boot is indeed the only project using DT for its internal configuration why should we care?
For example, let's imagine you build TF-A, and TF-A is configured and bundled with a device tree that gets passed along to U-Boot (using OF_BOARD). Why on earth should TF-A be aware of internal DM implementation details and build a device tree containing u-boot,dm-pre-reloc, u-boot,dm-spl, dm-tpl, and every other non-upstreamed nodes we have? Another example would be the public key that we shoehorn on the DT. In commit ddf67daac39d ("efi_capsule: Move signature from DTB to .rodata") I tried to get rid of that because since I was aware of the dt-schema conformance and honestly having the capsule public portion of the key there makes little sense. Unfortunately, that got reverted in commit 47a25e81d35c8 with a bogus commit message as well. So again imagine building TF-A, which is a first-stage bootloader and has no understanding of UEFI whatsoever, asking the TF-A project to start injecting public keys around that has no idea why or how they will be used.
Can you imagine how the device tree would look like in a couple of years from now if we allow *every* project to add its own special config needs in there? So perhaps we should take a step back, agree that some level of config is needed, identify the common options, and add that to the spec instead of dumping everything that doesn't fit somewhere else in there.
We already have reserved-memory, flash layout and other things which don't relate to hardware. I would love to somehome get past this fundamental discussion which seems to come up every time we get close to making progress
Most of the nodes we already have were used across projects and made sense to all of them. U-Boot might need to reserve some memory and so does linux etc etc. Some other nodes make nosense at all to and they just serve internal ABI implementation details. I can't possibly fathom how these would be justifiable. On top of all that, there's a huge danger here. How are you planning on separating arbitrary entries from various projects?
I think in some ways this is the whole point of at least what I'm asking for. It's fine to say "Here is the mechanism to remove nodes / properties from the device tree". BUT adding entries to that list MUST document where someone tried to upstream and explain that this is something that belongs in the device tree because it is useful to everyone.
And we don't disagree on that either. That's why the link to the FWU discussion was there (although it should have been in a doc and not in a mail). I am not arguing against adding nodes, I am arguing that we shouldn't rush them and that there's zero chance that we manage to upstream everything and keep some level of sanity on the spec. So, since U-Boot is currently using the DT for its own configuration needs, not having the ability to provide a DT that conforms to the spec and hope that we can upstream everything will just delay all of SystemReady 2.0 conformance efforts (and is unrealistic IMHO).
What I am afraid is going to happen here is simple. If a project doesn't use DT to configure itself and wants to provide a DT to U-Boot, then are you going to say "Can you please inject various DT nodes in the tree because U-Boot *needs* them and they are now part of the spec"? Anyway, it's not up to me to decide here, I am just saying what makes sense to me.
What's the difference between that and "If a project doesn't use DT to configure itself and wants to provide a DT to Linux, ..." ?
See the example above with TF-A, I hope that clears it up.
Thanks /Ilias
-- Tom