linux-kernel - Re: [PATCH v2 3/4] mfd: add support for Allwinner SoCs ADC

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Date:	Mon, 25 Jul 2016 11:55:32 +0200
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	Jonathan Cameron <jic23@...nel.org>,
	Quentin Schulz <quentin.schulz@...e-electrons.com>,
	jdelvare@...e.com, linux@...ck-us.net, knaack.h@....de,
	lars@...afoo.de, pmeerw@...erw.net, wens@...e.org,
	linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
	linux-iio@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	thomas.petazzoni@...e-electrons.com,
	antoine.tenart@...e-electrons.com
Subject: Re: [PATCH v2 3/4] mfd: add support for Allwinner SoCs ADC

On Fri, Jul 22, 2016 at 02:55:56PM +0100, Lee Jones wrote:
> On Thu, 21 Jul 2016, Maxime Ripard wrote:
> 
> > 1;4205;0c
> > On Thu, Jul 21, 2016 at 01:12:53PM +0100, Lee Jones wrote:
> > > On Wed, 20 Jul 2016, Jonathan Cameron wrote:
> > > 
> > > > On 19/07/16 08:31, Lee Jones wrote:
> > > > > On Mon, 18 Jul 2016, Jonathan Cameron wrote:
> > > > > 
> > > > >> On 15/07/16 10:59, Quentin Schulz wrote:
> > > > >>> The Allwinner SoCs all have an ADC that can also act as a touchscreen
> > > > >>> controller and a thermal sensor. For now, only the ADC and the thermal
> > > > >>> sensor drivers are probed by the MFD, the touchscreen controller support
> > > > >>> will be added later.
> > > > >>>
> > > > >>> Signed-off-by: Quentin Schulz <quentin.schulz@...e-electrons.com>
> > > > >> Hmm. Previous patch includes the header this one creates.  Ordering issue?
> > > > >> The depends kind of prevents build failures by ensuring that can't be built
> > > > >> until this one is in place, but it is certainly an ugly way to do it.
> > > > >>
> > > > >> Few little bits innline.
> > > > >>> ---
> > > > >>>
> > > > >>> v2:
> > > > >>>  - add license headers,
> > > > >>>  - reorder alphabetically includes,
> > > > >>>  - add SUNXI_GPADC_ prefixes for defines,
> > > > >>>
> > > > >>>  drivers/mfd/Kconfig                 |  14 +++
> > > > >>>  drivers/mfd/Makefile                |   2 +
> > > > >>>  drivers/mfd/sunxi-gpadc-mfd.c       | 197 ++++++++++++++++++++++++++++++++++++
> > > > >>>  include/linux/mfd/sunxi-gpadc-mfd.h |  23 +++++
> > > > >>>  4 files changed, 236 insertions(+)
> > > > >>>  create mode 100644 drivers/mfd/sunxi-gpadc-mfd.c
> > > > >>>  create mode 100644 include/linux/mfd/sunxi-gpadc-mfd.h
> > > > > 
> > > > > [...]
> > > > > 
> > > > >>> +static struct mfd_cell sun6i_gpadc_mfd_cells[] = {
> > > > >>> +	{
> > > > >>> +		.name	= "sun6i-a31-gpadc-iio",
> > > > >>> +		.resources = adc_resources,
> > > > >>> +		.num_resources = ARRAY_SIZE(adc_resources),
> > > > >>> +	}, {
> > > > >>> +		.name = "iio_hwmon",
> > > > >> I still really dislike using this to force the probe of that driver but
> > > > >> kind of up to the hwmon / mfd guys on this.
> > > > > 
> > > > > Can you at least say *why* you don't like it?
> > > > It just feels odd to have an mfd child that isn't really dependent
> > > > on the mfd hardware itself.
> > > > 
> > > > Still if you are happy, mfd is your domain and my objections were
> > > > as you probably noticed not that strong - or well described!)
> > > > 
> > > > So I'm fine with this.
> > > 
> > > I see.  So it's not actually part of the same IP/chip?
> > 
> > The chip has a temperature sensor, and we want to expose that
> > temperature through IIO.
> > 
> > But we don't really have the choice on how we probe iio-hwmon
> > here. The binding was already there, and we have to keep it.
> 
> What binding?

The binding introduced for the original driver this serie aims to
replace:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/input/touchscreen/sun4i.txt

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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