linux-kernel - Re: [PATCH v2 1/6] powerpc/pseries/iommu: Create defines for operations in ibm,ddw-applicable

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Message-ID: <0d3ee444-f528-673e-48f9-633138398543@ozlabs.ru>
Date:   Thu, 2 Jul 2020 10:43:49 +1000
From:   Alexey Kardashevskiy <aik@...abs.ru>
To:     Leonardo Bras <leobras.c@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Ram Pai <linuxram@...ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/6] powerpc/pseries/iommu: Create defines for
 operations in ibm,ddw-applicable



On 02/07/2020 10:36, Leonardo Bras wrote:
> On Thu, 2020-07-02 at 10:21 +1000, Alexey Kardashevskiy wrote:
>>> enum {
>>>        DDW_QUERY_PE_DMA_WIN,
>>>        DDW_CREATE_PE_DMA_WIN,
>>>        DDW_REMOVE_PE_DMA_WIN,
>>>
>>>        DDW_APPLICABLE_SIZE
>>> }
>>> IMO, it looks better than all the defines before.
>>>
>>> What do you think?
>>
>> No, not really, these come from a binary interface so the reader of this
>> cares about absolute numbers and rather wants to see them explicitly.
> 
> Makes sense to me.
> I am still getting experience on where to use enum vs define. Thanks
> for the tip!
> 
> Using something like 
> enum {
> 	DDW_QUERY_PE_DMA_WIN = 0,
> 	DDW_CREATE_PE_DMA_WIN = 1,
> 	DDW_REMOVE_PE_DMA_WIN = 2,
> 
> 	DDW_APPLICABLE_SIZE
> };
> 
> would be fine too?


This is fine too.


> Or should one stick to #define in this case?

imho a matter of taste but after some grepping it feels like #define is
mostly used which does not mean it is a good idea. Keep it enum and see
if it passed mpe's filter :)



-- 
Alexey