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    Subject[RFC v2 0/4] i2c/of: switch I2C IP cores at runtime via OF_DYNAMIC
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    I know this is gonna be a controversial series, but we have a usecase for this :)

    This series allows an I2C bus to switch between multiple masters, i.e. a
    n-to-1-demuxer. This is not hot-switching because connected I2C slaves will be
    re-instantiated. It is meant to select the best I2C core at runtime once the
    task is known. Example: Prefer i2c-gpio over another I2C core because of HW
    errata affecting your current runtime configuration.

    It works by using OF_DYNAMIC and en-/disabling the i2c parent as needed. See
    the binding docs for more details. Because this is largely using OF_DYNAMIC, I
    decided to post the whole series to the dt list.

    Changes since RFC v1:

    * gracefully handle if i2c adapters are not present at runtime
    (driver not loaded yet)
    * added more documentation and examples
    * properly put the i2c adapters after use
    * respect PAGE_SIZE in sysfs_show

    This has been tested on a Renesas Lager board switching between i2c-gpio and
    two different IP cores (i2c-rcar and i2c-sh_mobile). The rebinding seems to be
    working as expected. However, in practice, I couldn't use the HDMI i2c slaves
    with another controller yet, because the rcar-du driver OOPSes when unbinding.
    This seems unrelated to this series because it can also be triggered via
    sysfs-unbind. soc-camera also had problems properly cleaning up on unbind, a
    patch for this already has been sent. So, this series is for sure a good test
    for the unbind path of drivers.

    Let me know what you think.

    Thanks,

    Wolfram


    Wolfram Sang (4):
    of: make of_mutex public
    dt-bindings: i2c: mux: demux-pinctrl: add bindings
    i2c: mux: demux-pinctrl: add driver
    ARM: shmobile: r8a7790: rework dts to use i2c demuxer

    .../devicetree/bindings/i2c/i2c-demux-pinctrl.txt | 155 ++++++++++++
    arch/arm/boot/dts/r8a7790-lager.dts | 141 +++++++----
    drivers/i2c/muxes/Kconfig | 9 +
    drivers/i2c/muxes/Makefile | 2 +
    drivers/i2c/muxes/i2c-demux-pinctrl.c | 276 +++++++++++++++++++++
    drivers/of/of_private.h | 1 -
    include/linux/of.h | 2 +
    7 files changed, 532 insertions(+), 54 deletions(-)
    create mode 100644 Documentation/devicetree/bindings/i2c/i2c-demux-pinctrl.txt
    create mode 100644 drivers/i2c/muxes/i2c-demux-pinctrl.c

    --
    2.1.4



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