linux-kernel - Re: [PATCH 1/2] iio: vadc: Qualcomm SPMI PMIC voltage ADC driver

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Date:	Wed, 10 Sep 2014 12:49:55 +0300
From:	"Ivan T. Ivanov" <iivanov@...sol.com>
To:	Stanimir Varbanov <svarbanov@...sol.com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Pawel Moll <pawel.moll@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Kumar Gala <galak@...eaurora.org>,
	Mark Rutland <mark.rutland@....com>,
	Grant Likely <grant.likely@...aro.org>,
	Jonathan Cameron <jic23@...nel.org>,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Hartmut Knaack <knaack.h@....de>,
	Angelo Compagnucci <angelo.compagnucci@...il.com>,
	Doug Anderson <dianders@...omium.org>,
	Fugang Duan <B38611@...escale.com>,
	Johannes Thumshirn <johannes.thumshirn@....de>,
	Jean Delvare <jdelvare@...e.de>,
	Philippe Reynes <tremyfr@...oo.fr>,
	Lee Jones <lee.jones@...aro.org>,
	Josh Cartwright <joshc@...eaurora.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	David Collins <collinsd@...eaurora.org>
Subject: Re: [PATCH 1/2] iio: vadc: Qualcomm SPMI PMIC voltage ADC driver

Hi,

On Tue, 2014-09-09 at 15:49 +0300, Stanimir Varbanov wrote:
> On 09/09/2014 01:32 PM, Arnd Bergmann wrote:
> > On Monday 08 September 2014 18:30:00 Stanimir Varbanov wrote:
> >>>>> These numbers all look hardware specific, so why put macros into the
> >>>>> device tree rather than using them directly?
> >>>>
> >>>> The idea was to use #defines in DT nodes when we need to overwrite the
> >>>> adc channel parameters, see example in 2/2 how it will be used.
> >>>
> >>> I don't understand. The node in the example has
> >>>
> >>> +               /* Channel node */
> >>> +               usb_id_nopull@39 {
> >>> +                       qcom,channel = <VADC_LR_MUX10_USB_ID>;
> >>> ...
> >>> +               };
> >>>
> >>>
> >>> And VADC_LR_MUX10_USB_ID is defined to 0x39.  How is this helping anything?
> >>> You just introduce an artificial dependency on the header file, which makes
> >>> it a mess to merge the patches or do updates, and anybody who needs to
> >>> make updates to this now has to go through the same pain, to update the
> >>> dts files, the driver and the binding document in lockstep.
> >>>
> >>> Why not remove the qcom,channel property completely and use a 'reg'
> >>> property with #address-cells=<1>, #size-cells=<0> and put the number
> >>> directly in there, with no need for obfuscation macros?
> >>
> >> OK thanks for the remarks. I will fix this mess.
> >>
> >> I hope you are expecting to see this:
> >>
> >> pmic_vadc: vadc@...0 {
> >>         #address-cells = <1>;
> >>         #size-cells = <0>;
> >>         #io-channel-cells = <1>;
> >>         io-channel-ranges;
> >>
> >>         usb_id_nopull@39 {
> >>                 reg = <0x39>;
> >>         };
> >> };
> >>
> >> and use the vadc channel from usb device node
> >>
> >> usb {
> >>         ...
> >>         io-channels = <&pmic_vadc 0x39>;

I believe this will be more readable and clear.

	     io-channels = <&pmic_vadc VADC_LR_MUX10_USB_ID>;

I would like to keep channels definitions macros in DT header.

Regards,
Ivan



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