On Mon, 2017-01-09 at 12:55 +0000, David Laight wrote: > From: Joe Perches > > Sent: 07 January 2017 18:33 > > Shifting and masking various types can be made a bit > > simpler to read by using the available kernel macros. > > ... > > - ew32(TDBAH, (tdba >> 32)); > > - ew32(TDBAL, (tdba & 0x00000000ffffffffULL)); > > + ew32(TDBAH, upper_32_bits(tdba)); > > + ew32(TDBAL, lower_32_bits(tdba)); > > Personally I find the original code easier to understand > since I don't have to look up another silly macro.
It's already a pretty common usage and I believe the naming is fairly obvious. Also you don't have to count the "f" characters to see how many bits are being used. After about 6 consecutive chars, it can be error prone. The leading zeros? ugh. The ULL too. $ git grep -w -E "upper_32_bits|lower_32_bits" | wc -l 1569 > I'd normally not even explicitly mask the low bits > relying on the implicit truncation of the assignment. Relying on implicit behaviors can be noisy when compilers complain about implicit conversions and truncations. > At least modern compilers aren't stupid enough to add two > 'mask with 0xff' instructions for: > *uchar_ptr = (unsigned char)(foo & 0xff); I agree it's visual noise.
