linux-kernel - Re: [PATCH 4/4] platform/chrome: i2c: i2c-cros-ec-tunnel: Convert i2c tunnel to MFD Cell

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Date:   Fri, 22 Nov 2019 02:42:53 -0800
From:   Guenter Roeck <groeck@...gle.com>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Raul E Rangel <rrangel@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Wolfram Sang <wsa@...-dreams.de>, Akshu.Agrawal@....com,
        Guenter Roeck <groeck@...omium.org>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        linux-i2c@...r.kernel.org, Benson Leung <bleung@...omium.org>
Subject: Re: [PATCH 4/4] platform/chrome: i2c: i2c-cros-ec-tunnel: Convert i2c
 tunnel to MFD Cell

On Fri, Nov 22, 2019 at 12:03 AM Lee Jones <lee.jones@...aro.org> wrote:
>
> On Thu, 21 Nov 2019, Guenter Roeck wrote:
>
> > On Thu, Nov 21, 2019 at 1:11 PM Raul E Rangel <rrangel@...omium.org> wrote:
> > >
> > > If the i2c-cros-ec-tunnel driver is compiled into the kernel, it is
> > > possible that i2c-cros-ec-tunnel could be probed before cros_ec_XXX
> > > has finished initializing and setting the drvdata. This would cause a
> > > NULL pointer panic.
> > >
> > > Converting this driver over to an MFD solves the problem and aligns with
> > > where the cros_ec is going.
> > >
> >
> > I thought the mfd maintainer objects to the use of the mfd API outside
> > drivers/mfd. Did that change recently ?
>
> It hasn't changed, although I don't see that here?
>
Sorry, I was confused.

Guenter

> > > Signed-off-by: Raul E Rangel <rrangel@...omium.org>
> > > ---
> > > You can now see the device node lives under the mfd device.
> > >
> > > $ find /sys/bus/platform/devices/cros-ec-dev.0.auto/cros-ec-i2c-tunnel.12.auto/ -iname firmware_node -exec ls -l '{}' \;
> > > /sys/bus/platform/devices/cros-ec-dev.0.auto/cros-ec-i2c-tunnel.12.auto/firmware_node -> ../../../../../../LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:1c/PNP0C09:00/GOOG0004:00/GOOG0012:00
> > > /sys/bus/platform/devices/cros-ec-dev.0.auto/cros-ec-i2c-tunnel.12.auto/i2c-9/firmware_node -> ../../../../../../../LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:1c/PNP0C09:00/GOOG0004:00/GOOG0012:00
> > > /sys/bus/platform/devices/cros-ec-dev.0.auto/cros-ec-i2c-tunnel.12.auto/i2c-9/i2c-10EC5682:00/firmware_node -> ../../../../../../../../LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:1c/PNP0C09:00/GOOG0004:00/GOOG0012:00/10EC5682:00
> > >
> > >  drivers/i2c/busses/i2c-cros-ec-tunnel.c | 36 +++++++++----------------
> > >  drivers/mfd/cros_ec_dev.c               | 19 +++++++++++++
> > >  2 files changed, 32 insertions(+), 23 deletions(-)
>
> --
> Lee Jones [李琼斯]
> Linaro Services Technical Lead
> Linaro.org │ Open source software for ARM SoCs
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