Device Tree Evolution Project - call notes - 6th November

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]



Hey folks,

I'm sharing the notes from our regular meeting that was held today. We
continued discussion around our two main topics: System DT and how to
work with a new/shared repo for DT data.

More details about the meeting etc. at the end.

Attendees
=========
SteveM - Arm
ArndB - Linaro
KumarG - Linaro
LoicP - ST
MarkB - Arm
MathieuP - Linaro
RobH - Arm
SaravanaK - Google
StefanoS - Xilinx
TomasE - Xilinx
TrikokS - Qualcomm
VincentG - Linaro
WarnerL - FreeBSD
DonH - Linaro
Frank Rowand - ???

Notes
=====

* Steve will check into opening up the docs a bit

* Arnd spoke to people at ELC-E, particularly with Frank who seems
  unhappy to change the status quo.

* We should push some more public discussion about System DT
  + Stefano has bindings etc. ready to send out in the next couple of days

* Need to respond more to discussions on moving the DT data
  + More discussion from other projects to support this, and describe
    how they use things will help   
  + Push the stability idea
    + Better for U-Boot and FreeBSD devs too, of course
    + We want people to complain more when things change and cause
      breakages - share the pain
    + Do the FreeBSD people have some CI that can help to identify
      breakage? Some limited stuff here, they want to automate more
      going forwards
      - Need more backwards-and-forwards testing to identify regressions in Linux too
      - FreeBSD people also using DT for other arches like powerpc and
        mips, but arm/arm64 are the main targets
   + Why is a hardware description being kept in with the Linux kernel
   (only)? This was meant to be a short-term stopgap until firmware
   provided DTs...

* Engineer assignments from ST
  + Benjamin to contribute to system DT
  + Alexander to work on DT identifcation at runtime
    - Set up meeting with him, RH, GL, SM to discuss details. Anybody else?

Wider discussion about moving things out
----------------------------------------

* FreeBSD people have had breakages come from Linux, but unhelpful
  responses when they report issues

* Other projects add extra interfaces in DT - Android, etc.

* What about DT on hardware that would never run Linux? Where should
  that be managed? Bindings have been taken in the past in Linux even
  without drivers.

* Can we find a model that works here for everybody without causing
  too much extra grief for the Linux development model?

* Olof has suggested a split - just a core set of DT in Linux, with
  lots of boards / variants externally

* Keeping DTS, headers, bindings together matters (as already
  discussed previously)

* Rob and Grant have mentioned a patch to build DTBs from the kernel
  using DTSs from an external repo
  + Effort seems to have died out

* Can we organise a sprint to work on stuff and generate a prototype?
  + Maybe a good way to drive the discussion forward
  + Demonstrate working ideas?
  + Maybe, but time and travel are awkward.

* Need to open up discussion more to the normal lists
  + include more community people, definitely

* What are the blockers to progress here? A few options to think
  about; any others?
  + Can we demonstrate an external DTS repo being used for various
    projects? Rebasing tree (ijc) is an example
  + External repo with DT stuff that the kernel can pull from directly
    at build time?
  + External repo, sync things into the kernel
    periodically. Automation to help
  + Git submodule?

* Headers are already a source of pain with separation - different
  maintainers. Driver/header/DTS need to be in sync. Would also be a
  problem with external repo

* Would Olof's tool for generating DTs help? Not so much - still a
  sync problem

* How often are platform folks shipping working DT with the firmware?
  + Depends a lot on the market - some do, some don't
  + Things like Android phones are mixed - some data from the
    firmware, then some applied on top. Move to mainline kernels is
    part of this.
  + On powerpc, almost all platforms ship with DTB in the firmware
  + RISC-V plan is to always have DTB in the firmware too
  + Do we have example of platforms shipping DTBs where newer kernels
    stop working due to incompatibilities? Yes - Apple powermac, some
    IBM machines
  + With ACPI, firmware can cause problems and people end up shipping
    workarounds. Firmware updates are rare

* Are wasting time talking about stability here maybe? Compatibility
  is something people spend a lot of time on.
  + FreeBSD people have sometimes added overlays to override bugs in
    the provided DT
  + While bringing up DT support on a platform, compat is basically
    ignored. Only start worrying about compat when something is
    considered "stable", or maybe to stick with what's shipped by
    firmware.

* Let's look at the actions from the chat at SAN19

* Warner definitely interested in a meetup etc. if we have one

* Add a pointer to the devicetree-spec posting on the mail dt list
  + also send to U-Boot folks
  + FreeBSD? Zephyr? anybody else?

Background information about DTE
================================

Linaro engineers are working on a range of initiatives in the DT
space, collected together as a project called Device Tree Evolution
(DTE). We hold a discussion call every second Wednesday at 
1700 GMT / 1200 EST / 0900 PST. If you would like to be invited, please
ask me (Steve McIntyre).

This is a summary of the notes from the most recent meeting. I aim to
tidy up and post the meeting notes shortly after each meeting. The raw
notes are published at

https://docs.google.com/document/d/e/2PACX-1vRVDrVFWjIOascqZFCO--T8pIqyFB_MDh9cvgyoqhI6Y0tqaA9TcCcvQhcmxi5IY7CG44JfIrCdAUDL/pub

For more information about DTE, see:

 * https://www.linaro.org/engineering/core/devicetree-evolution/
 * https://www.linaro.org/assets/pdf/Linaro-White-Paper--Device-Tree-Evolution.pdf

Cheers,
-- 
Steve McIntyre                                steve.mcintyre@xxxxxxxxxx
<http://www.linaro.org/> Linaro.org | Open source software for ARM SoCs




[Index of Archives]     [Device Tree]     [Linux Driver Backports]     [Video for Linux]     [Linux USB Devel]     [Linux Audio Users]     [Photos]     [Yosemite Photos]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Yosemite Backpacking]

  Powered by Linux