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

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Date:   Thu, 2 Jul 2020 10:21:27 +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 01/07/2020 23:28, Leonardo Bras wrote:
> On Wed, 2020-07-01 at 18:16 +1000, Alexey Kardashevskiy wrote:
>>
>> On 24/06/2020 16:24, Leonardo Bras wrote:
>>> Create defines to help handling ibm,ddw-applicable values, avoiding
>>> confusion about the index of given operations.
>>>
>>> Signed-off-by: Leonardo Bras <leobras.c@...il.com>
>>> ---
>>>  arch/powerpc/platforms/pseries/iommu.c | 40 +++++++++++++++-----------
>>>  1 file changed, 23 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
>>> index 6d47b4a3ce39..68d2aa9c71a8 100644
>>> --- a/arch/powerpc/platforms/pseries/iommu.c
>>> +++ b/arch/powerpc/platforms/pseries/iommu.c
>>> @@ -39,6 +39,11 @@
>>>  
>>>  #include "pseries.h"
>>>  
>>> +#define DDW_QUERY_PE_DMA_WIN	0
>>> +#define DDW_CREATE_PE_DMA_WIN	1
>>> +#define DDW_REMOVE_PE_DMA_WIN	2
>>> +#define DDW_APPLICABLE_SIZE	3
>>
>> #define DDW_APPLICABLE_SIZE  (DDW_REMOVE_PE_DMA_WIN + 1)
>>
>> thanks,
> 
> Thanks for the feedback!
> About this (and patch #2), would it be better to use enum ?
> 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.


-- 
Alexey