On 08/03/2012 11:30 PM, Tejun Heo wrote:
>> I think hash_for_for_each_possible() is useful if the comparison
>> > condition is more complex than a simple comparison of one of the
>> > object members with the key - there's no need to force it on all the
>> > users.
> I don't know. What's the difference? In terms of LOC, it might even
> not save any thanks to the extra function definition, right? I don't
> think it's saving enough complexity to justify a separate rather
> unusual interface.
The function definition itself is just a macro, for example:
#define MM_SLOTS_HASH_CMP(mm_slot, obj) ((mm_slot)->mm == (obj))
As an alternative, what do you think about simplifying that to be just a 'cond' instead of a function? Something like:
hash_get(&mm_slots_hash, mm, struct mm_slot, hash, mm);
In that case, the last param ("mm") will get unrolled to a condition like this:
if ((obj)->mm == key)
Which will be simple and easy for the user.
The only reason I want to keep this interface is that most cases I've stumbled so far were easy short comparisons of a struct member with the key, and I don't want to make them more complex than they need to be. I probably will switch hash_get() to use hash_for_each_possible() as well, which will cut down on how hash_get() is a separate case.
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