On 28.08.2024 9:06 PM, Andy Shevchenko wrote: > On Wed, Aug 28, 2024 at 8:40 PM Maximilian Luz <luzmaximilian@xxxxxxxxx> wrote: >> On 8/28/24 6:56 PM, Andy Shevchenko wrote: >>> On Wed, Aug 28, 2024 at 12:10 PM Maximilian Luz <luzmaximilian@xxxxxxxxx> wrote: > > ... > >>> Yes, and software nodes for DT are quite strange things! Why can't you >>> simply fix the DT to begin with? >> >> For the ARM/DT variants we could do that. But we still have to deal with >> the x86/ACPI ones here. > > So, then fix it there! Currently it's an abuse of software nodes > inside the Linux kernel. > >> So for me it makes more sense to have it unified >> and just deal with everything in this module. > > I understand the desire, but DT is DT and ACPI is ACPI, they are > different despite having some common APIs in the Linux kernel. > Moreover, DT has a validation tools and everything, making that being > a software nodes has at least these disadvantages: > - no official schema that must be supported and users are known of > - no validation done > - bloating of the Linux kernel binary and hence memory footprint Arguably the last point isn't very strong.. DT also has to store some strings and pointers to represent devices > >> Also, if we consider that at some point we might get ACPI PEP support (I >> know, far fetched right now): With that, ACPI on ARM might be feasible >> and then we'd have to manage the same thing in two places... > > This (PEP) is something I have no knowledge about. But I think it's > still orthogonal to the software nodes usage. The PEP (Power Engine Plugin) unfortunately is the reason we can't have ACPI-based boot on WoA platforms.. This two-or-three-digit megabyte Windows driver hardcodes almost everything related to the on-SoC power management (buses, clocks, etc.) and only uses the bare minimum ACPI it needs to connect devices to a bus or get notifications on standard events.. > >> And lastly, the EC subdevices are quite contained and I don't see them >> interacting with any other components in the DT, so it's more of a >> stylistic choice where to put them. > > They are still part of hardware and DT describes hardware. Unfortunately the "Surface Aggregator Module" is just a firmware exposed on some range of MCUs running MSFT's code.. Given how.. peculiarly the "bus" that it hosts """devices""" on is constructed (5-level-deep hierarchy without it making much sense beyond maaaybe the first two), it's not really easy to describe in DT in a way that would be both true to the bigger picture and make enough sense to convince the DT maintainers, I don't think Konrad
