linux-kernel - Re: [PATCH v3 2/3] pinctrl: renesas: Renesas RZ/N1 pinctrl driver

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Message-ID: <20180918133353.GT16851@w540>
Date:   Tue, 18 Sep 2018 15:33:53 +0200
From:   jacopo mondi <jacopo@...ndi.org>
To:     Phil Edworthy <phil.edworthy@...esas.com>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Simon Horman <horms@...ge.net.au>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/3] pinctrl: renesas: Renesas RZ/N1 pinctrl driver

Hi Phil,

On Tue, Sep 18, 2018 at 11:55:16AM +0000, Phil Edworthy wrote:
> Hi Jacopo,
>

[snip]

> > > +
> > > +/*
> > > + * Structure detailing the HW registers on the RZ/N1 devices.
> > > + * Both the Level 1 mux registers and Level 2 mux registers have the
> > > +same
> > > + * structure. The only difference is that Level 2 has additional MDIO
> > > +registers
> > > + * at the end.
> > > + */
> > > +struct rzn1_pinctrl_regs {
> > > +	union {
> > > +		u32	conf[170];
> > > +		u8	pad0[0x400];
> >
> > Is pad0 actually used?
> No, it's just to implement the padding. Would you prefer not using a union
> here?

Oh, I did the math wrong, to me it was (32*170 > 8*400) but it's
actually (32*170 < 8*1024).

Also using a struct to define the memory region layout confused me and
I was about to ask "WHY ARE YOU RESERVING MEMORY HERE???" but this
type is just used for pointers, and it makes accessing HW locations
nicer actually (thanks Geert for having saved me a silly comment on this).

Cheers
   j


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