Re: [PATCH] asm-generic: io: Fix ioread16/32be and iowrite16/32be

From: Michal Simek
Date: Fri Feb 08 2013 - 03:24:17 EST

2013/2/8 Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>:
> On Thu, Feb 7, 2013 at 3:18 PM, Michal Simek <michal.simek@xxxxxxxxxx> wrote:
>> Fix ioreadXXbe and iowriteXXbe functions which did
>> additional little endian conversion on native big endian systems.
>> Using be_to_cpu (cpu_to_be) conversions with __raw_read/write
>> functions have resolved it.
>> Signed-off-by: Michal Simek <michal.simek@xxxxxxxxxx>
>> CC: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
>> CC: Arnd Bergmann <arnd@xxxxxxxx>
>> CC: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
>> CC: Will Deacon <will.deacon@xxxxxxx>
>> CC: linux-arch@xxxxxxxxxxxxxxx
> I have one question (see below). Apart from that:
> Acked-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
>> -#define ioread16be(addr) be16_to_cpu(ioread16(addr))
>> +#define ioread16be(addr) __be16_to_cpu(__raw_readw(addr))
> Why did you change it to the __beX_to_cpu variant with underscores?

The question could be probably different. Why are they even defined?
I have grepped the kernel and all archs use these generic macros

include/linux/byteorder/generic.h:94:#define be32_to_cpu __be32_to_cpu
include/linux/byteorder/generic.h:106:#define be32_to_cpup __be32_to_cpup
include/linux/byteorder/generic.h:118:#define be32_to_cpus __be32_to_cpus

What about to remove them?

Back to you question. I can't remember particular reason for that maybe
just experience that __ versions should be the fastest kernel implementation.


Michal Simek, Ing. (M.Eng)
w: p: +42-0-721842854
Maintainer of Linux kernel - Microblaze cpu -
Maintainer of Linux kernel - Xilinx Zynq ARM architecture
Microblaze U-BOOT custodian and responsible for u-boot arm zynq platform
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