Re: [RFC PATCH 1/4] IPMI: Add one interface to get more info of low-level IPMI device

[Corey Minyard <minyard@acm.org>]

On 10/14/2010 08:07 PM, ykzhao wrote:
>
>> The way you are doing it, there is no need for a refcount, since you are
>> making a copy of the data.
>>
>> Is a copy or a pointer better?  A pointer is generally preferred, it
>> keeps from having to either store data on the stack or dynamically
>> allocate it for the copy.  But it's not a huge deal in this case.  A
>> pointer will require you to dynamically allocate the smi_info structure
>> so you can free it separately.  But then only the top-level put routine
>> is required, it can simply free the structure if the refcount is zero.
>>      
> When the pointer mechanism is used, we will have to allocate the
> smi_info structure dynamically. Every time the function of
> ipmi_get_smi_info, it will be allocated dynamically. And if it fails in
> the allocation, we can't return the expected value.
>    
Well, you misunderstand.  You allocate one copy when the SMI info is 
created.  And you return a pointer to that with the refcount 
incremented.  No need to allocate a new one on each call.  Use the 
refcounts to know when to free it.

> But when the copy is used, it will be much simpler.  It is the caller's
> responsibility to prepare the corresponding data structure. They can
> define it on stack. Of course they can also dynamically allocate it.
>
> Can we choose the copy mechanism to make it much simpler?
>    
Sure, I think I already said this :).  Just get rid of the refcount stuff.

-corey