Re: [Qemu-devel] [PATCH] vmxnet: Don't use bswap_64 for constants

[Richard Henderson <rth@twiddle.net>]

On 2013-03-27 16:42, Andreas Färber wrote:
> Am 27.03.2013 19:47, schrieb Richard Henderson:
>> This macro is used in the context of defining enum values.
>> We can't use a function call in that case.
>>
>> Cc: qemu-trivial@nongnu.org
>> Signed-off-by: Richard Henderson <rth@twiddle.net>
>> ---
>>   hw/vmxnet3.h | 10 +++++++++-
>>   1 file changed, 9 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/vmxnet3.h b/hw/vmxnet3.h
>> index 7db0c8f..cd9ac85 100644
>> --- a/hw/vmxnet3.h
>> +++ b/hw/vmxnet3.h
>> @@ -37,7 +37,15 @@
>>   #define __packed QEMU_PACKED
>>
>>   #if defined(HOST_WORDS_BIGENDIAN)
>> -#define const_cpu_to_le64(x) bswap_64(x)
>> +#define const_cpu_to_le64(x) \
>> +        (((x & 0x00000000000000ffULL) << 56) | \
>> +         ((x & 0x000000000000ff00ULL) << 40) | \
>> +         ((x & 0x0000000000ff0000ULL) << 24) | \
>> +         ((x & 0x00000000ff000000ULL) <<  8) | \
>> +         ((x & 0x000000ff00000000ULL) >>  8) | \
>> +         ((x & 0x0000ff0000000000ULL) >> 24) | \
>> +         ((x & 0x00ff000000000000ULL) >> 40) | \
>> +         ((x & 0xff00000000000000ULL) >> 56))
>
> Being a macro, shouldn't this better use (x) for operator precedence?

It doesn't matter for this usage.

Nor, according to other threads that appeared on the list today, is this
the right fix, since the bswap itself turns out to be bogus.

Myself, I never tested the driver code, just fixed the compile error.


r~