Re: [RFC] i2c: device-tree: Handling child nodes which are not i2c devices

On 2016-08-01 11:19, Tomeu Vizoso wrote:

On 15 April 2016 at 17:35, Jon Hunter [off-list ref] wrote:

quoted

Hi all,

For Tegra we have an i2c device for display port, namely the display
port auxiliary channel (or dpaux) as specified by the display port
standard. If an design using Tegra does not utilise the display port
interface, then the pads assigned to the dpaux can be re-assigned to
another generic i2c controller (i2c6 for Tegra124/210). In other words,
the pads can be re-used for a generic i2c interface.

The registers that control whether the pads are mapped to the dpaux or
i2c6 are located in the dpaux register space. Therefore, I am looking at
adding pin controller support for dpaux so that i2c6 can request these
pads if it is enabled and I was hoping to add a pinmux node the to dpaux
device in device-tree to do this. For example, something like ...

        dpaux@0,545c0000 {
                ...

                /* pinctrl node */
                pinmux {
                        ...
                };
        };

Although the above works, when doing this I noticed that when the device
booted, I would seeing the following error messages on boot ...

 i2c i2c-5: of_i2c: modalias failure on ...

These error messages being caused by the new pinmux node because it is
not recognised as an i2c device. To avoid this error messages we have
come up with a couple solutions but wanted to get some feedback on the
best approach.

Hi,

I'm finding this issue as well on Rockchip SoCs, this is the specific
node that is raising this warning when an adapter is registered with
it:

edp: dp@ff970000 {
    compatible = "rockchip,rk3288-dp";
    ...
    ports {
        ...
    };
};

Has there been any agreement since this thread waned?

Thanks,

Tomeu

This is currently soaking in linux-next:

dt-bindings: i2c: Add support for 'i2c-bus' subnode
https://git.kernel.org/cgit/linux/kernel/git/wsa/linux.git/commit/?h=i2c/for-next&id=98b00488459e

i2c: core: Add support for 'i2c-bus' subnode
https://git.kernel.org/cgit/linux/kernel/git/wsa/linux.git/commit/?h=i2c/for-next&id=7e4c224abfe8

Cheers,
Peter

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