[PATCH] drm: don't link DP aux i2c adapter to the hardware device node

[Andrzej Hajda]

On 05.04.2017 14:04, Thierry Reding wrote:
> On Wed, Apr 05, 2017 at 10:52:32AM +0200, Lucas Stach wrote:
>> Hi Rob,
>>
>> Am Mittwoch, den 29.03.2017, 08:56 -0500 schrieb Rob Herring:
>>> On Mon, Jan 23, 2017 at 10:33 AM, Thierry Reding
>>> <thierry.reding at gmail.com> wrote:
>>>> On Fri, Jan 13, 2017 at 06:36:30PM +0100, Lucas Stach wrote:
>>>>> The i2c adapter on DP AUX is purely a software construct. Linking
>>>>> it to the device node of the parent device is wrong, as it leads to
>>>>> 2 devices sharing the same device node, which is bad practice, as
>>>> Who says that two devices can't share the same device node? It's done
>>>> all the time.
>>> It's done *some of the time* and I would not consider it best practice.
>>>
>>>>> well as the i2c trying to populate children of the i2c adapter by
>>>>> looking at the child device nodes of the parent device.
>>>> A set of patches landed in v4.9 to work around this issue in a better
>>>> way. See:
>>>>
>>>>         98b00488459e dt-bindings: i2c: Add support for 'i2c-bus' subnode
>>>>         7e4c224abfe8 i2c: core: Add support for 'i2c-bus' subnode
>>> What does this buy us? I don't see why this needs to be in DT either.
>>> Contrary to popular belief, DT is not the only way to instantiate
>>> devices, C code can still do it.
>>>
>>> Also, if this one line removal has no side effects, then how was it
>>> even needed? We can always add it back if there's some argument for
>>> why it is needed.
>> Okay, so I take this as you mostly agreeing with the rationale of this
>> patch.
> For some general background on this: I was originally using this for DP
> support on Tegra (though that ended up never getting merged because of a
> particularily frustrating episode of trying to get better link training
> support into the core helpers) and use it as a means to obtain the I2C
> controller used for DDC. On Tegra, and I suspect other devices as well,
> the DP AUX controller is separate from the encoder, so the idea was to
> link them together using a standard ddc-i2c-bus phandle.
>
> I ended up not needing that because the encoder and DP AUX controller
> are so tightly linked on Tegra that I need direct access to the DP AUX
> anyway and can therefore directly get the I2C controller from that.
>
> If there aren't any other users of this, I suppose we could simply
> remove the line. Should someone turn up in the future and require the
> I2C controller to be looked up from a phandle we could add it again,
> at which point we'd have to investigate again how to get rid of the
> errors.
>
> Acked-by: Thierry Reding <treding at nvidia.com>

It looks like the patch has been accepted but not merged. Who can pick
it up? or is it OK if I put it int drm-misc?

Regards
Andrzej