On Sat, May 17, 2014 at 9:12 PM, Joe Perches <joe@xxxxxxxxxxx> wrote:
> On Sat, 2014-05-17 at 21:00 -0700, David Matlack wrote:
> []
>> diff --git a/drivers/staging/slicoss/slicoss.c b/drivers/staging/slicoss/slicoss.c
> []
>> +static inline u16 __reduce(u32 checksum)
>> +{
>> + u16 lower_16 = checksum & 0xFFFF;
>> + u16 upper_16 = (checksum >> 16) & 0xFFFF;
>> +
>> + checksum = lower_16 + upper_16;
>> +
>> + if (checksum > 65535)
>> + checksum -= 65535;
>> +
>> + return checksum;
>> +}
>
> The if seems unnecessary.
>
> Perhaps declare a u16 return var or use
>
> return lower_16 + upper_16;
I agree it's fishy... but using overflow doesn't produce the same result:
(u16) 65536 == 0
65536 - 65535 == 1
Now which is the correct result, I have no idea. The eeprom on this device is
small (0x80 bytes max, not enough to trigger overflow) and I have no
documentation, so I don't know how to test :(
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