linux-kernel - Re: [PATCH] spi/xilinx: Cast ioread32/iowrite32 function pointers

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Message-ID: <CAPybu_0OWLZeEFMByrrDg7HOfjAYbOnAoazLac-E8KV-mKSJSg@mail.gmail.com>
Date:	Thu, 29 Jan 2015 23:14:46 +0100
From:	Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	"moderated list:ARM/S5P EXYNOS AR..." 
	<linux-arm-kernel@...ts.infradead.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Michal Simek <michal.simek@...inx.com>,
	Mark Brown <broonie@...nel.org>,
	Sören Brinkmann <soren.brinkmann@...inx.com>,
	linux-spi <linux-spi@...r.kernel.org>
Subject: Re: [PATCH] spi/xilinx: Cast ioread32/iowrite32 function pointers

Hello Arnd

On Thu, Jan 29, 2015 at 11:11 PM, Arnd Bergmann <arnd@...db.de> wrote:
>> > I think the definitions in include/asm-generic/iomap.h are actually wrong,
>> > as they lack a const:
>> >
>> >     extern unsigned int ioread8(void __iomem *);
>> >     extern unsigned int ioread16(void __iomem *);
>> >     extern unsigned int ioread16be(void __iomem *);
>> >     extern unsigned int ioread32(void __iomem *);
>> >     extern unsigned int ioread32be(void __iomem *);
>> >
>> > Note that the definitions in include/asm-generic/io.h do have the const:
>> >
>> >     static inline u8 ioread8(const volatile void __iomem *addr)
>> >     static inline u16 ioread16(const volatile void __iomem *addr)
>> >     static inline u32 ioread32(const volatile void __iomem *addr)
>> >     static inline u16 ioread16be(const volatile void __iomem *addr)
>> >     static inline u32 ioread32be(const volatile void __iomem *addr)
>>
> I think we don't need the 'volatile' keyword here. The main reason
> we have it on readl() is to shut up the compiler when dealing with
> ancient driver code that annotates iomem pointers as volatile.
>
> This is generally considered a (minor) driver mistake though, and
> modern drivers that for some reason use ioread*() typically don't
> do that (or they get a warning).

What about the different return type? u8 vs int
Thanks

-- 
Ricardo Ribalda
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