linux-kernel - Re: [PATCH v6 1/3] dt-bindings: pinctrl: renesas,rzn1-pinctrl: documentation

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Date:   Thu, 27 Sep 2018 11:25:36 -0500
From:   Rob Herring <robh@...nel.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Phil Edworthy <phil.edworthy@...esas.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mark Rutland <mark.rutland@....com>,
        Jacopo Mondi <jacopo@...ndi.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Simon Horman <horms@...ge.net.au>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v6 1/3] dt-bindings: pinctrl: renesas,rzn1-pinctrl:
 documentation

On Thu, Sep 27, 2018 at 05:15:54PM +0200, Geert Uytterhoeven wrote:
> On Thu, Sep 27, 2018 at 3:59 PM Phil Edworthy <phil.edworthy@...esas.com> wrote:
> > The Renesas RZ/N1 device family PINCTRL node description.
> >
> > Based on a patch originally written by Michel Pollet at Renesas.
> >
> > Signed-off-by: Phil Edworthy <phil.edworthy@...esas.com>
> > Reviewed-by: Jacopo Mondi <jacopo+renesas@...ndi.org>
> > ---
> > v6:
> >  - Instead of combining the pin nr and func into a single element, use
> >    a pair of 8-bit elements.
> 
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/pinctrl/renesas,rzn1-pinctrl.txt
> 
> > +- Pin multiplexing sub-nodes:
> > +  A pin multiplexing sub-node describes how to configure a set of
> > +  (or a single) pin in some desired alternate function mode.
> > +  A single sub-node may define several pin configurations.
> > +  Please refer to pinctrl-bindings.txt to get to know more on generic
> > +  pin properties usage.
> > +
> > +  The allowed generic formats for a pin multiplexing sub-node are the
> > +  following ones:
> > +
> > +  node-1 {
> > +      pinmux = /bits/ 8 <PIN_NR MUX_FUNC>, <PIN_NR MUX_FUNC>, ... ;
> > +      GENERIC_PINCONFIG;
> > +  };
> 
> and
> 
> > +  Example:
> > +  A serial communication interface with a TX output pin and an RX input pin.
> > +
> > +  &pinctrl {
> > +       pins_uart0: pins_uart0 {
> > +               pinmux = /bits/ 8 <
> > +                       103 RZN1_FUNC_UART0_I   /* UART0_TXD */
> > +                       104 RZN1_FUNC_UART0_I   /* UART0_RXD */
> > +               >;
> > +       };
> > +  };
> 
> So the above is in response to Rob's comment on v4:
> 
> | > +#define RZN1_MUX(_gpio, _func) \
> | > +       (((RZN1_FUNC_##_func) << 8) | (_gpio))
> |
> | I'm not a fan of token pasting and it also goes against kernel style.
> | If every other Renesas platform is doing this, then fine. Otherwise,
> | you can express it in pretty much the same (source) space:
> |
> | pinmux = <RZN1_MUX_UART0_I 104>;
> |
> | Yes, this is 2 cells instead of 1, but if you care about space, you
> | can use 8 or 16 bit size.
> 
> I'm not so much impressed by the "/bits/ 8" part.
> No other pinctrl bindings uses this.
> We do have RZA1_PINMUX() and STM32_PINMUX() macros.

Yes, but those aren't doing token pasting which was my complaint here.

> Rob: Is this really what you intended?

Do whatever is most consistant. If you want a macro to shift fields, 
then fine.

Rob