RE: Question about the function,ni_stc_dma_channel_select_bitfield

[Hartley Sweeten]

On Wednesday, May 06, 2015 7:06 AM, nick wrote:
> On 2015-05-06 05:10 AM, Ian Abbott wrote:
>> On 06/05/15 01:22, nick wrote:
>>> Greetings All,
>>> I am wondering if in the function,ni_stc_dma_channel_select_bitfield the line:
>>> return 1 << channel;
>>> is guaranteed to be below the threshold that guarantees us to not overflow on
>>> a unsigned 32 integer due to bit wise shifting to the left.
>>> Thanks Nick
>>>
>> 
>>     if (channel < 4)
>>         return 1 << channel;
>> 
>> So, yes.
>> 
> This should be commented in my option as this is not common knowledge
> unless you known the hardware specs really well. If I should send in
> a patch adding a comment here please let me known.

A comment is not necessary. The code explicitly states that channel (an unsigned var)
needs to be < 4 for the bit shift to happen.

Hartley