[PATCH 0/7] devicetree cleanup for i2c muxes/arbs/gates

[Peter Rosin]

Hi!

The nxp pca9541 chip does not have any devicetree bindings.
When trying to write such bindings matching the implementation,
I stumbled upon something which I did not like. I had to
give the node holding the i2c child bus a 'reg' property that
is left unused and is really odd to explain from a devicetree
point of view. It really is a leftover from the fact that linux
implements i2c arbitrators (and i2c gates) using the i2c mux
code. See this thread for history [1].

This series resolves the issues, and maintains backwards compat
with old device trees (well, one could, in theory, create a
device tree that would break with these changes, but my guess
is that the odds for that happening inadvertedly are high...)

This should also help Crestez Dan Leonard with the mpu6050
series containing the changes for its auxiliary i2c master [2],
especially if you also consider the recent (very similar) changes
from Jon Hunter that adds an optional 'i2c-bus' subnode [3].

If this is ok, I will follow up with patches for other drivers
so that they inform the i2c mux core if they are muxes, arbs or
gates. As stated, they will continue to work with these changes,
so there is no huge rush.

The mux core does not really need to differentiate between
arbitrators and gates. Should they be folded? What to call them
in that case?

Cheers,
Peter

[1] https://lkml.org/lkml/2016/6/27/203
[2] https://lkml.org/lkml/2016/5/18/355
[3] https://patchwork.ozlabs.org/patch/641934/

Peter Rosin (7):
  dt-bindings: i2c: add support for 'i2c-mux' subnode
  dt-bindings: i2c: add support for 'i2c-arb' subnode
  dt-bindings: i2c: add support for 'i2c-gate' subnode
  dt-bindings: i2c: add bindings for nxp,pca9541
  i2c: mux: add support for 'i2c-mux', 'i2c-arb' and 'i2c-gate' DT
    subnodes
  i2c: pca9541: add device tree binding
  i2c: pca954x: add device tree binding

 .../bindings/i2c/i2c-arb-gpio-challenge.txt        |  8 +---
 Documentation/devicetree/bindings/i2c/i2c-arb.txt  | 35 ++++++++++++++++
 Documentation/devicetree/bindings/i2c/i2c-gate.txt | 35 ++++++++++++++++
 Documentation/devicetree/bindings/i2c/i2c-mux.txt  | 23 ++++++++---
 .../devicetree/bindings/i2c/nxp,pca9541.txt        | 29 ++++++++++++++
 MAINTAINERS                                        |  2 +
 drivers/i2c/i2c-mux.c                              | 44 +++++++++++++++++----
 drivers/i2c/muxes/i2c-mux-pca9541.c                |  8 ++++
 drivers/i2c/muxes/i2c-mux-pca954x.c                | 46 ++++++++++++++++------
 include/linux/i2c-mux.h                            |  8 +++-
 10 files changed, 205 insertions(+), 33 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/i2c/i2c-arb.txt
 create mode 100644 Documentation/devicetree/bindings/i2c/i2c-gate.txt
 create mode 100644 Documentation/devicetree/bindings/i2c/nxp,pca9541.txt

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