Messages in this thread | | | Date | Thu, 14 Mar 2019 10:09:52 GMT | From | George Spelvin <> | Subject | Re: [PATCH 1/5] lib/sort: Make swap functions more generic |
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On Sat, 09 Mar 2019 at 23:19:49 +0300, Andrey Abramov wrote: >> Although I'm thinking of: >> >> static bool __attribute_const__ >> is_aligned(const void *base, size_t size, unsigned char align) >> { >> unsigned char lsbits = (unsigned char)size; >> >> (void)base; >> #ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS >> lsbits |= (unsigned char)(uintptr_t)base; >> #endif >> return (lsbits & (align - 1)) == 0; >> } >> >> Any preference? > I think it would be better.
>> I find "u32s" confusing; I keep reading the "s" as "signed" rather >> than a plural. >> >> How about one of: >> swap_bytes / swap_ints / swap_longs >> swap_1 / swap_4 / swap_8 > > In my opinion "swap_bytes / swap_ints / swap_longs" are the most readable.
On Thu, 14 Mar 2019 at 11:29:58 +0200, Andy Shevchenko wrote: > On Sat, Mar 09, 2019 at 03:53:41PM +0000, lkml@sdf.org wrote: >> static bool __attribute_const__ >> is_aligned(const void *base, size_t size, unsigned char align) >> { >> unsigned char lsbits = (unsigned char)size; >> #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS >> (void)base; >> #else >> lsbits |= (unsigned char)(uintptr_t)base; >> #endif >> return (lsbits & (align - 1)) == 0; >> } > >> Any preference? > > This one looks better in a sense we don't suppress the warnings when it's > not needed.
>>> For such primitives that operates on top of an arrays we usually >>> append 's' to the name. Currently the name is misleading. >>> >>> Perhaps u32s_swap(). >> >> I don't worry much about the naming of static helper functions. >> If they were exported, it would be a whole lot more important! >> >> I find "u32s" confusing; I keep reading the "s" as "signed" rather >> than a plural. > > For signedness we use prefixes; for plural, suffixes. I don't see the point of > confusion. And this is in use in kernel a lot. > >> How about one of: >> swap_bytes / swap_ints / swap_longs >> swap_1 / swap_4 / swap_8 > > longs are ambiguous, so I would prefer bit-sized types.
I already implemented Andrey's suggestions, which were the exact opposite of yours.
Pistols at dawn?
>>>> +#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS >>> >>> Why #ifdef is better than if (IS_ENABLED()) ? >> >> Because CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is bool and not >> tristate. IS_ENABLED tests for 'y' or 'm' but we don't need it >> for something that's only on or off. > > There is IS_BUILTIN(), though it's a common practice to use IS_ENABLED() > even for boolean options (I think because of naming of the macro).
Well, as I said earlier, #ifdef is the most common form in the kernel. It's also the shortest to write, and I like the fact that it slightly simpler. (Admittedly, "IS_ENABLED" does not take a lot of brain power to interpret, but it *is* one more macro that might be hiding magic.)
So I'm not inclined to change it without a substantial reason.
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