[PATCH] Cosmetic: fix endianness convertions in read[wlq]().

[PATCH] Cosmetic: fix endianness convertions in read[wlq]().

[Krzysztof Halasa]

Signed-off-by: Krzysztof Hałasa <khc@pm.waw.pl>

diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
index 3f0f5a2..8480acf 100644
--- a/include/asm-generic/io.h
+++ b/include/asm-generic/io.h
@@ -35,8 +35,8 @@
 #endif
 
 #define readb __raw_readb
-#define readw(addr) __le16_to_cpu(__raw_readw(addr))
-#define readl(addr) __le32_to_cpu(__raw_readl(addr))
+#define readw(addr) __cpu_to_le16(__raw_readw(addr))
+#define readl(addr) __cpu_to_le32(__raw_readl(addr))
 
 #ifndef __raw_writeb
 #define __raw_writeb(v,a)	(__chk_io_ptr(a), *(volatile unsigned char __force  *)(a) = (v))
@@ -59,7 +59,7 @@ static inline u64 __raw_readq(const volatile void __iomem *addr)
 {
 	return *(const volatile u64 __force *) addr;
 }
-#define readq(addr) __le64_to_cpu(__raw_readq(addr))
+#define readq(addr) __cpu_to_le64(__raw_readq(addr))
 
 static inline void __raw_writeq(u64 b, volatile void __iomem *addr)
 {

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Re: [PATCH] Cosmetic: fix endianness convertions in read[wlq]().

[Sascha Hauer]

On Sat, May 05, 2012 at 11:36:40PM +0200, Krzysztof Halasa wrote:
> Signed-off-by: Krzysztof Hałasa <khc@pm.waw.pl>
> 
> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
> index 3f0f5a2..8480acf 100644
> --- a/include/asm-generic/io.h
> +++ b/include/asm-generic/io.h
> @@ -35,8 +35,8 @@
>  #endif
>  
>  #define readb __raw_readb
> -#define readw(addr) __le16_to_cpu(__raw_readw(addr))
> -#define readl(addr) __le32_to_cpu(__raw_readl(addr))
> +#define readw(addr) __cpu_to_le16(__raw_readw(addr))
> +#define readl(addr) __cpu_to_le32(__raw_readl(addr))

This seems wrong. readw/l are supposed to do little endian reads and that
is exactly what the code you remove does: It reads in cpu native
endianess and interprets that as a little endian word which is then
converted into cpu native endian word.
(Also the code is copied from the kernel which makes me quite confident
that it's correct)

Sascha


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Re: [PATCH] Cosmetic: fix endianness convertions in read[wlq]().

[Krzysztof Halasa]

Sascha Hauer <s.hauer@pengutronix.de> writes:

>> -#define readw(addr) __le16_to_cpu(__raw_readw(addr))
>> -#define readl(addr) __le32_to_cpu(__raw_readl(addr))
>> +#define readw(addr) __cpu_to_le16(__raw_readw(addr))
>> +#define readl(addr) __cpu_to_le32(__raw_readl(addr))
>
> This seems wrong. readw/l are supposed to do little endian reads and that
> is exactly what the code you remove does: It reads in cpu native
> endianess and interprets that as a little endian word which is then
> converted into cpu native endian word.
> (Also the code is copied from the kernel which makes me quite confident
> that it's correct)

Well... That's right. I forgot the PCI on ARM is set in order-preserving
mode. This means that while the peripherals (u32) are accessed simply
with __raw_readl(), on PCI bus __raw_readl() yields wrong-endian value
(le32 instead of u32). I wonder how it passes sparse.
-- 
Krzysztof Halasa

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