On 1/19/2016 10:44 AM, Yuanhan Liu wrote:
> On Tue, Jan 19, 2016 at 01:51:30AM +0000, Xie, Huawei wrote:
>> On 1/19/2016 9:34 AM, Yuanhan Liu wrote:
>>> On Mon, Jan 18, 2016 at 05:07:51PM +0000, Xie, Huawei wrote:
>>>> .On 1/15/2016 12:34 PM, Yuanhan Liu wrote:
>>>>> Modern (v1.0) virtio pci device defines several pci capabilities.
>>>>> Each cap has a configure structure corresponding to it, and the
>>>>> cap.bar and cap.offset fields tell us where to find it.
>>>>>
>>>> [snip]
>>>>> +
>>>>> +static inline void
>>>>> +io_write64_twopart(uint64_t val, uint32_t *lo, uint32_t *hi)
>>>>> +{
>>>>> + io_write32((uint32_t)val, lo);
>>>>> + io_write32(val >> 32, hi);
>>>> Firstly your second iowrite32 doesn't do the conversion.
>>> Because it's not necessary. The first one is for retrieving the low 32
>>> bits.
>> I don't mean the shift operation, but the conversion from 64bit to 32bit.
>> Same applied to below.
> It's more than a casting here: it's same as "val & (1<<32 - 1)", as
> stated above, to retrieve the low 32 bits.
>
> I know it still could work without it, but, hey, what's wrong to make
> it explicit?
Say x = val, y = val >> 32, both with (uint32_t) or both not. Be
consistent and simple.
>
> --yliu
>
