linux-kernel - Re: [PATCH v2 1/2] spi: Add Renesas R-Car Gen3 RPC SPI controller driver

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Date:   Thu, 6 Dec 2018 10:12:11 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     masonccyang@...c.com.tw
Cc:     Marek Vasut <marek.vasut@...il.com>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Mark Brown <broonie@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Simon Horman <horms@...ge.net.au>, juliensu@...c.com.tw,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        linux-spi <linux-spi@...r.kernel.org>, zhengxunli@...c.com.tw
Subject: Re: [PATCH v2 1/2] spi: Add Renesas R-Car Gen3 RPC SPI controller driver

Hi Mason,

On Thu, Dec 6, 2018 at 8:31 AM <masonccyang@...c.com.tw> wrote:
> > >> Re: [PATCH v2 1/2] spi: Add Renesas R-Car Gen3 RPC SPI controller driver
> > >>
> > >> On 12/03/2018 10:18 AM, Mason Yang wrote:
> > >> > Add a driver for Renesas R-Car Gen3 RPC SPI controller.
> > >> >
> > >> > Signed-off-by: Mason Yang <masonccyang@...c.com.tw>

> > >> > +   xfercnt = xferpos;
> > >> > +   rpc->xferlen = xfer[--xferpos].len;
> > >> > +   rpc->cmd = RPC_SMCMR_CMD(((u8 *)xfer[0].tx_buf)[0]);
> > >>
> > >> Is the cast needed ?
> > >
> > > yes!
> >
> > Why ?
>
> Get a compiler warning due to tx_bug is void *, as Geert replied.
>
> Using get_unaligned(), patched code would be
> ---------------------------------------------------------------
>  rpc->cmd = RPC_SMCMR_CMD(get_unaligned((u8 *)xfer[0].tx_buf));
> ----------------------------------------------------------------

Using get_unaligned(0 is a bit strange for accessing a single byte quantity.
Please keep the normal pointer dereference (including the cast).

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