[U-Boot] [PATCH] omap3evm: Clean-up EVM detection code.

Albert ARIBAUD
2010-12-02T19:32:09Z

Le 02/12/2010 19:51, Wolfgang Denk a ?crit :
> Dear Albert ARIBAUD,
>
> In message<4CF7C7F4.6030803@free.fr> you wrote:
>>
>>> Well, an u8 is as good a data type as any other. The available range
>>> of 0...255 seems more than sufficient to store the needed
>>> information, so why should I waste 4 bytes of storage when a single
>>> byte is sufficient as well?
>>
>> You don't necessarily use only one byte when declaring an u8 instead of
>> an int, because the next declaration may have alignment requirements
>> that will cause the compiler to skip bytes after the u8. Besides, u8 is
>
> The compiler / linker may (or may not) optimize this and collect
> variables of similar alignment. An "int foo;" is likely to end in
> .bss segment, while an "char foo;" will probably show up in .sbss - I
> don;t know how good or bad the current situation for ARM is, but I'm
> sure it is improving (look for example at all the microoptimizations
> done by Linaro).

There is only a single .bss for ARM.

>> not "as good a data type" as any other, it is a specific data type
>> whereas 'int' is the native data type of the platform, supposed to be
>> the most natural to deal with for the cpu -- 32-bit for an ARM.
>
> Can an ARM CPU not read1s and write single bytes, too?

It can, but for many of its operations, it can only work with 32-bit data.

> Let's stop this here.

Understood.

> Best regards,
>
> Wolfgang Denk

Amicalement,
--
Albert.