From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joe Perches Subject: Re: [RFC PATCH] intel: Use upper_32_bits and lower_32_bits Date: Mon, 09 Jan 2017 05:33:10 -0800 Message-ID: <1483968790.2106.10.camel@perches.com> References: <7a5cfe63cad3ef4badc30cbc2185a5bfb9250fd8.1483813334.git.joe@perches.com> <063D6719AE5E284EB5DD2968C1650D6DB025AC14@AcuExch.aculab.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: Julia Lawall , "intel-wired-lan@lists.osuosl.org" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" To: David Laight , Jeff Kirsher Return-path: In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6DB025AC14@AcuExch.aculab.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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.