linux-kernel - Re: [RFC 3/3] ARM: e3xx: Add header file for pinctrl constants

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Date:	Fri, 6 Nov 2015 08:01:25 -0800
From:	Moritz Fischer <moritz.fischer@...us.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
	Rob Herring <robh+dt@...nel.org>,
	"pawel.moll@....com" <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>, devicetree@...r.kernel.org
Subject: Re: [RFC 3/3] ARM: e3xx: Add header file for pinctrl constants

Hi Arnd,

On Fri, Nov 6, 2015 at 12:54 AM, Arnd Bergmann <arnd@...db.de> wrote:
> On Thursday 05 November 2015 15:41:23 Moritz Fischer wrote:
>> +/* Pin names for the E31x usecase */
>> +#define E31X_TX_BANDSEL_2      "DB_1"
>> +#define E31X_RX1B_BANDSEL_0    "DB_3"
>> +#define E31X_RX1B_BANDSEL_1    "DB_5"
>> +#define E31X_VCTXRX2_V2                "DB_7"
>> +#define E31X_TX_ENABLE1A       "DB_9"
>> +#define E31X_TX_ENABLE2A       "DB_11"
>> +#define E31X_TX_BANDSEL_0      "DB_12"
>
> Why not put the strings directly into the .dts files and change the
> lookup table in the driver accordingly:
>
> +static const struct pinctrl_pin_desc e3xx_pins[] = {
> +       /* pin0 doesn't exist */
> +       PINCTRL_PIN(1, "TX_BANDSEL_2"),
> +       PINCTRL_PIN(3, "RX1B_BANDSEL_0"),
> +       PINCTRL_PIN(5, "RX1B_BANDSEL_1"),
> +       PINCTRL_PIN(7, "VCTXRX2_V2"),

That's actually the way I initially had it, however the pin names
literally changed
in the schematic depending on which daughter-board you stick into the slot.
So my plan was to add the #defines for the second daughter-board in a
follow up patch
once the pin assignment is final. This would allow me to have something like:

pins = E31X_TX_BANDSEL_2;
output-low;

in one .dts, while having something like

pins = E33X_TX_BANDSEL_2
output low;

in the second dts

The other option would have been to stick a e31x_pins and a e33x_pins
into the driver,
and set them according to a compatible string or "ettus,daughterboard"
property on probe.

Does that make sense, or do you think there's a cleaner / better way
to achieve this sort of behavior?

Thanks for your feedback!

Cheers,
Moritz
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