linux-kernel - Re: [PATCH 2/5] include: add setbits32/clrbits32/clrsetbits32/setbits64/clrbits64/clrsetbits64 in linux/setbits.h

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Date:   Fri, 07 Sep 2018 15:00:40 -0500
From:   Scott Wood <oss@...error.net>
To:     Corentin Labbe <clabbe@...libre.com>, Gilles.Muller@...6.fr,
        Julia.Lawall@...6.fr, agust@...x.de, alexandre.torgue@...com,
        alistair@...ple.id.au, benh@...nel.crashing.org, carlo@...one.org,
        davem@...emloft.net, galak@...nel.crashing.org,
        joabreu@...opsys.com, khilman@...libre.com,
        maxime.ripard@...tlin.com, michal.lkml@...kovi.net,
        mpe@...erman.id.au, mporter@...nel.crashing.org,
        nicolas.palix@...g.fr, paulus@...ba.org, peppe.cavallaro@...com,
        tj@...nel.org, vitb@...nel.crashing.org, wens@...e.org
Cc:     cocci@...teme.lip6.fr, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-ide@...r.kernel.org,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        netdev@...r.kernel.org, linux-sunxi@...glegroups.com
Subject: Re: [PATCH 2/5] include: add
 setbits32/clrbits32/clrsetbits32/setbits64/clrbits64/clrsetbits64 in
 linux/setbits.h

On Fri, 2018-09-07 at 19:41 +0000, Corentin Labbe wrote:
> This patch adds setbits32/clrbits32/clrsetbits32 and
> setbits64/clrbits64/clrsetbits64 in linux/setbits.h header.
> 
> Signed-off-by: Corentin Labbe <clabbe@...libre.com>
> ---
>  include/linux/setbits.h | 55
> +++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 55 insertions(+)
>  create mode 100644 include/linux/setbits.h
> 
> diff --git a/include/linux/setbits.h b/include/linux/setbits.h
> new file mode 100644
> index 000000000000..3e1e273551bb
> --- /dev/null
> +++ b/include/linux/setbits.h
> @@ -0,0 +1,55 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __LINUX_SETBITS_H
> +#define __LINUX_SETBITS_H
> +
> +#include <linux/io.h>
> +
> +#define __setbits(readfunction, writefunction, addr, set) \
> +	writefunction((readfunction(addr) | (set)), addr)
> +#define __clrbits(readfunction, writefunction, addr, mask) \
> +	writefunction((readfunction(addr) & ~(mask)), addr)
> +#define __clrsetbits(readfunction, writefunction, addr, mask, set) \
> +	writefunction(((readfunction(addr) & ~(mask)) | (set)), addr)
> +#define __setclrbits(readfunction, writefunction, addr, mask, set) \
> +	writefunction(((readfunction(addr) | (seti)) & ~(mask)), addr)
> +
> +#define setbits32(addr, set) __setbits(readl, writel, addr, set)
> +#define setbits32_relaxed(addr, set) __setbits(readl_relaxed,
> writel_relaxed, \
> +					       addr, set)
> +
> +#define clrbits32(addr, mask) __clrbits(readl, writel, addr, mask)
> +#define clrbits32_relaxed(addr, mask) __clrbits(readl_relaxed,
> writel_relaxed, \
> +						addr, mask)

So now setbits32/clrbits32 is implicitly little-endian?  Introducing new
implicit-endian accessors is probably a bad thing in general, but doing it
with a name that until this patchset was implicitly big-endian (at least on
powerpc) seems worse.  Why not setbits32_le()?


> +
> +#define clrsetbits32(addr, mask, set) __clrsetbits(readl, writel, addr,
> mask, set)
> +#define clrsetbits32_relaxed(addr, mask, set) __clrsetbits(readl_relaxed, \
> +							   writel_relaxed,
> \
> +							   addr, mask, set)
> +
> +#define setclrbits32(addr, mask, set) __setclrbits(readl, writel, addr,
> mask, set)
> +#define setclrbits32_relaxed(addr, mask, set) __setclrbits(readl_relaxed, \
> +							   writel_relaxed,
> \
> +							   addr, mask, set)

What's the use case for setclrbits?  I don't see it used anywhere in this
patchset (not even in the coccinelle patterns), it doesn't seem like it would
be a common pattern, and it could easily get confused with clrsetbits.

-Scott