linux-kernel - Re: [PATCH] i2c/busses: Add i2c-icy for I2C on m68k/Amiga

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Message-ID: <CAMuHMdWr8VNBBVjgcu9wtdby-0pznEtg=GeVmAcrk78Of7gwNA@mail.gmail.com>
Date:   Tue, 13 Aug 2019 08:53:14 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Max Staudt <max@...as.org>
Cc:     Linux I2C <linux-i2c@...r.kernel.org>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        "Linux/m68k" <linux-m68k@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Subject: Re: [PATCH] i2c/busses: Add i2c-icy for I2C on m68k/Amiga

Hi Max,

On Tue, Aug 13, 2019 at 12:21 AM Max Staudt <max@...as.org> wrote:
> On 08/12/2019 11:37 AM, Geert Uytterhoeven wrote:
> >> +       iowrite8(val, address);
> >
> > As this is on a Zorro bus, z_writeb()?
>
> I forgot to ask about this.
>
> What is the reasoning behind having a separate z_writeb() for Zorro?
> As far as I can see in arch/m68k/include/asm this maps 1:1 to a direct memory access, and it prohibits cross-arch code as in i2c-elektor.

write*() and friends are intended for PCI, and thus little endian, while
the Zorro bus is big endian. For byte accesses this doesn't matter,
obviously.

Note that this predates iowrite*(), which does have *be variants.
If you want to add compile-testing to your driver, using iowrite*() is fine.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds