Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 2 Apr 2024 10:13:31 -0700 | Subject | Re: [PATCH 1/4] x86/cpu: Add and use new CPUID region helper | From | Dave Hansen <> |
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On 3/25/24 05:24, Huang, Kai wrote: > > Nit: > >> + >> +/* Returns true if the leaf exists and @value was populated */ > > ^ is ?
It's a subtle difference, but I think it's better as I wrote it. Returning true happens *after* the value _was_ populated.
>> +static inline bool get_cpuid_region_leaf(u32 leaf, enum cpuid_regs_idx reg, >> + u32 *value) >> +{ >> + u16 region = leaf >> 16; >> + u32 regs[4]; >> + >> + if (cpuid_region_max_leaf(region) < leaf) >> + return false; >> + >> + cpuid(leaf, ®s[CPUID_EAX], ®s[CPUID_EBX], >> + ®s[CPUID_ECX], ®s[CPUID_EDX]); >> + >> + *value = regs[reg]; >> + >> + return true; >> +} > > I found despite the get_cpuid_region_leaf() returns true/false, the return value > is never used in this series. Instead, this series uses below pattern: > > u32 data = 0; /* explicit initialization */ > > get_cpuid_region_leaf(leaf, ..., &data); > > Which kinda implies the 'data' won't be touched if the requested leaf isn't > supported I suppose? > > Since the return value is never used, should we consider just making this > function void?
I certainly considered it.
But I do think that get_cpuid_region_leaf() looks a lot more obviously correct and useful when it explicitly returns what it did, even if the existing callers don't take advantage of it.
I suspect it generates the same code either way.
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