Re: [PATCH] ARM: dts: rockchip: add i2c-bus subnode to edp

Heiko Stuebner
2016-10-21T08:26:02Z

Am Donnerstag, 20. Oktober 2016, 15:47:56 CEST schrieb Tomeu Vizoso:
> On 10/20/2016 03:45 PM, Heiko Stübner wrote:
> > Am Donnerstag, 20. Oktober 2016, 10:07:25 schrieb Tomeu Vizoso:
> >> Add an empty 'i2c-bus' subnode to the edp node just so that the I2C core
> >> doesn't attemp to parse the 'ports' subnode as containing i2c devices.
> >>
> >> This is to avoid spurious failure messages such as:
> >>
> >> i2c i2c-6: of_i2c: modalias failure on /dp@ff970000/ports
> >
> > On the one hand, the edp really has an i2c bus - with its only client the
> > EDID listening at 0x50 (and maybe 0x30).
> >
> > On the other hand, adding an empty bus to the (implementation independent)
> > devicetree just to make the Linux i2c subsystem happy sounds heavily like
> > a
> > implementation-specific hack, as the edp i2c bus doesn't leak into the
> > outside world otherwise.
> >
> > I guess this empty i2c bus not being part of the binding document points
> > heavily into the implementation-specific corner :-) .
> >
> > My short search on other patches touching this didn't reveal anything but
> > maybe this was already discussed somewhere and found to be ok?
>
> Here it is:
>
> http://www.spinics.net/lists/linux-tegra/msg27862.html

thanks ... I'm still not sure about the placeholder though, aka needing an
undocumented subnode to make a Linux error message silent.

In the thread you pointed to I also did not see any dt-maintainer involvement
pointing one way or another, but spinics is often not easy to navigate
threads, so I may have missed that.

> > Another option could be to just make of_i2c_register_device silent if
> > of_modalias_node returns -ENODEV?

Heiko

> >> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
> >> Cc: Randy Li <randy.li@rock-chips.com>
> >> Cc: Jon Hunter <jonathanh@nvidia.com>
> >> ---
> >>
> >> arch/arm/boot/dts/rk3288.dtsi | 5 +++++
> >> 1 file changed, 5 insertions(+)
> >>
> >> diff --git a/arch/arm/boot/dts/rk3288.dtsi
> >> b/arch/arm/boot/dts/rk3288.dtsi
> >> index 2f814ffeb605..94f4b7eecca2 100644
> >> --- a/arch/arm/boot/dts/rk3288.dtsi
> >> +++ b/arch/arm/boot/dts/rk3288.dtsi
> >> @@ -1075,6 +1075,11 @@
> >>
> >> };
> >>
> >> };
> >>
> >> };
> >>
> >> +
> >> + i2c-bus {
> >> + #address-cells = <1>;
> >> + #size-cells = <0>;
> >> + };
> >>
> >> };
> >>
> >> hdmi: hdmi@ff980000 {