On Thu, 13 Feb 2025, 21:06 Herve Codina, <herve.codina@xxxxxxxxxxx> wrote: > > Hi Phil, > > On Thu, 13 Feb 2025 20:15:06 +0000 > Phil Elwell <phil@xxxxxxxxxxxxxxx> wrote: > > > Once more, with plain text, which I'd hoped the Android GMail client > > would work out for itself. > > > > On Thu, 13 Feb 2025, 18:53 Herve Codina, <herve.codina@xxxxxxxxxxx> wrote: > > > > > > Hi Phil, > > > > > > On Thu, 13 Feb 2025 17:57:37 +0000 > > > Phil Elwell <phil@xxxxxxxxxxxxxxx> wrote: > > > > > > > On Thu, 13 Feb 2025 at 17:45, Andrew Lunn <andrew@xxxxxxx> wrote: > > > > > > > > > > > > Or do you mean a custom board, which has a CPU, RP1 and the button and > > > > > > > fan are directly on this custom board? You then want a board DTS which > > > > > > > includes all these pieces? > > > > > > > > > > > > That depends on whether you count the Raspberry Pi 5 as a custom board. > > > > > > > > > > So you mean the Pi 5 board would itself make use of the resources the > > > > > RP1 device has? They are not simply connected to headers for plugin > > > > > boards, but used by the main board? Hence you want to describe them in > > > > > the board .DTS file. > > > > > > > > That's correct. But even for plug-in devices, those which are on > > > > non-discoverable buses need overlays to declare them, which causes a > > > > problem when the overlay application happens before the kernel is > > > > started. > > > > > > > > > > Hum, I see. > > > > > > We worked on overlay usage on non-discoverable buses wired to a connector > > > and we did a talk about issues we are facing on at Plumber [0]. > > > > > > You can also find our big picture in [1] and a last contribution introducing > > > export-symbols feature in [2]. export-symbols is also under discussion on > > > some other threads. > > > > > > Also, we proposed the i2c bus extensions feature [3] whose goal is to allow > > > an addon board to add devices on an i2c bus provided by a base board and > > > wired to an connector the addon board is connected to. > > > > > > Maybe in your case, you can decouple resources (gpio, pwm) provided by the > > > addon board and used by the base board using also nexus node. > > > > > > We use a nexus node [4] (not presented at the Plumbers talk because the idea > > > came during 'out of talk' discussions in Plumbers) in order to allow our > > > addon board to use resources provided by the base board. > > > > > > In your case, if I understood, you are in the other direction but why not > > > using also a nexus node to decouple and translate resources in this other > > > direction ? > > > > > > Don't know if this idea can help but feel free to ask for some more > > > information if needed. > > > > Nexus nodes look interesting - I see them as adding a layer of > > abstraction such that, for example, boards can declare which of their > > specific resources performs a common function so that clients can > > treat them all the same. We do the same thing in a limited way by > > using common labels on nodes, but this goes much further. > > > > In the case of Pi 5 and RP1, I imagine you are proposing that the Pi 5 > > dtb declares the connector node and the overlay fills in the content > > with references to its GPIO controller, PWM controller etc. However, I > > think the overlay would also have to be board specific because it's > > not possible to patch part of a property from an overlay, so you'd end > > up overwriting the GPIO number as well as the controller reference. > > > > What is needed to make this work is the ability to cope with > > unresolved references in the base dtb, to be resolved as each overlay > > is applied, with runtime checking that each reference is resolved > > before it is used, all of which sounds like a nightmare. Plus, we > > really don't want to have to change the way all our camera and display > > overlays work on all Raspberry Pis just to accommodate somebody's idea > > of how RP1 should be handled. > > Just to be clear, my comments were not there to tell you how RP1 should > work. I just proposed ideas without trying to force anything and I can > fully understand that ideas proposed don't feed your needs. > > Sorry if my approach was misunderstood. I feel I've been misunderstood - I appreciate your ideas. Perhaps it would help if you could outline how you think we could apply your suggestions? Thanks, Phil
