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

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Date:	Mon, 08 Sep 2014 18:30:00 +0300
From:	Stanimir Varbanov <svarbanov@...sol.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	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>,
	"Ivan T. Ivanov" <iivanov@...sol.com>
Subject: Re: [PATCH 1/2] iio: vadc: Qualcomm SPMI PMIC voltage ADC driver

On 09/08/2014 01:19 PM, Arnd Bergmann wrote:
> On Monday 08 September 2014 11:13:50 Stanimir Varbanov wrote:
>> On 09/05/2014 03:26 PM, Arnd Bergmann wrote:
>>> On Friday 05 September 2014 15:14:33 Stanimir Varbanov wrote:
>>>> +       VADC_CHAN(LR_MUX1_BAT_THERM, 0)                 /* 0x30 */
>>>> +       VADC_CHAN(LR_MUX2_BAT_ID, 0)
>>>> +       VADC_CHAN(LR_MUX3_XO_THERM, 0)
>>>> +       VADC_CHAN(LR_MUX4_AMUX_THM1, 0)
>>>> +       VADC_CHAN(LR_MUX5_AMUX_THM2,by you  0)
>>>> +       VADC_CHAN(LR_MUX6_AMUX_THM3, 0)
>>>> +       VADC_CHAN(LR_MUX7_HW_ID, 0)
>>>> +       VADC_CHAN(LR_MUX8_AMUX_THM4, 0)
>>>> +       VADC_CHAN(LR_MUX9_AMUX_THM5, 0)
>>>> +       VADC_CHAN(AMUX_PU1, 0)
>>>> +       VADC_CHAN(AMUX_PU2, 0)
>>>> +       VADC_CHAN(LR_MUX3_BUF_XO_THERM_BUF, 0)          /* 0x3c */
>>>> +
>>>> +       VADC_CHAN(LR_MUX1_PU1_BAT_THERM, 0)             /* 0x70 */
>>>> +       VADC_CHAN(LR_MUX2_PU1_BAT_ID, 0)
>>>> +       VADC_CHAN(LR_MUX3_PU1_XO_THERM, 0)
>>>> +       VADC_CHAN(LR_MUX4_PU1_AMUX_THM1, 0)
>>>> +       VADC_CHAN(LR_MUX5_PU1_AMUX_THM2, 0)
>>>> +       VADC_CHAN(LR_MUX6_PU1_AMUX_THM3, 0)
>>>> +       VADC_CHAN(LR_MUX7_PU1_AMUX_HW_ID, 0)
>>>> +       VADC_CHAN(LR_MUX8_PU1_AMUX_THM4, 0)
>>>> +       VADC_CHAN(LR_MUX9_PU1_AMUX_THM5, 0)
>>>> +       VADC_CHAN(LR_MUX10_PU1_AMUX_USB_ID, 0)          /* 0x79 */
>>>> +       VADC_CHAN(LR_MUX3_BUF_PU1_XO_THERM_BUF, 0)      /* 0x7c */
>>>>
>>>
>>> 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>;
	io-channel-names = "usbidnopull";
};


-- 
regards,
Stan
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