On Wed, 2019-07-10 at 10:43 +0100, Russell King - ARM Linux admin wrote: > On Wed, Jul 10, 2019 at 11:17:31AM +0200, Johannes Berg wrote: > > On Tue, 2019-07-09 at 22:04 -0700, Joe Perches wrote: > > > These GENMASK uses are inverted argument order and the > > > actual masks produced are incorrect. Fix them. > > > > > > Add checkpatch tests to help avoid more misuses too. > > > > > > Joe Perches (12): > > > checkpatch: Add GENMASK tests > > > > IMHO this doesn't make a lot of sense as a checkpatch test - just throw > > in a BUILD_BUG_ON()? I tried that. It'd can't be done as it's used in declarations and included in asm files and it uses the UL() macro. I also tried just making it do the right thing whatever the argument order. Oh well. > My personal take on this is that GENMASK() is really not useful, it's > just pure obfuscation and leads to exactly these kinds of mistakes. > > Yes, I fully understand the argument that you can just specify the > start and end bits, and it _in theory_ makes the code more readable. > > However, the problem is when writing code. GENMASK(a, b). Is a the > starting bit or ending bit? Is b the number of bits? It's confusing > and causes mistakes resulting in incorrect code. A BUILD_BUG_ON() > can catch some of the cases, but not all of them. It's a horrid little macro and I agree with Russell. I also think if it existed at all it should have been GENMASK(low, high) not GENMASK(high, low). I
