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

From: Lee Jones <lee.jones@linaro.org>
To: Guenter Roeck <groeck@google.com>
Cc: Raul E Rangel <rrangel@chromium.org>,
	Enric Balletbo i Serra <enric.balletbo@collabora.com>,
	Wolfram Sang <wsa@the-dreams.de>,
	Akshu.Agrawal@amd.com, Guenter Roeck <groeck@chromium.org>,
	Chanwoo Choi <cw00.choi@samsung.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Alexandre Belloni <alexandre.belloni@bootlin.com>,
	linux-i2c@vger.kernel.org, Benson Leung <bleung@chromium.org>
Subject: Re: [PATCH 4/4] platform/chrome: i2c: i2c-cros-ec-tunnel: Convert i2c tunnel to MFD Cell
Date: Fri, 22 Nov 2019 08:03:19 +0000	[thread overview]
Message-ID: <20191122080319.GC3296@dell> (raw)
In-Reply-To: <CABXOdTeotUnO_7k9UycJ0vJEKV8pdZOjRrepDv5WVo5RmOLnEA@mail.gmail.com>

On Thu, 21 Nov 2019, Guenter Roeck wrote:

> On Thu, Nov 21, 2019 at 1:11 PM Raul E Rangel <rrangel@chromium.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?

> > Signed-off-by: Raul E Rangel <rrangel@chromium.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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