netdev - Re: [PATCH] net/dsa: remove unused macros to tame gcc warning

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Date:   Fri, 6 Nov 2020 08:39:34 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Andrew Lunn <andrew@...n.ch>, Alex Shi <alex.shi@...ux.alibaba.com>
Cc:     Vivien Didelot <vivien.didelot@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net/dsa: remove unused macros to tame gcc warning



On 11/6/2020 6:18 AM, Andrew Lunn wrote:
> On Fri, Nov 06, 2020 at 01:37:30PM +0800, Alex Shi wrote:
>> There are some macros unused, they causes much gcc warnings. Let's
>> remove them to tame gcc.
>>
>> net/dsa/tag_brcm.c:51:0: warning: macro "BRCM_EG_RC_SWITCH" is not used
>> [-Wunused-macros]
>> net/dsa/tag_brcm.c:53:0: warning: macro "BRCM_EG_RC_MIRROR" is not used
>> [-Wunused-macros]
>> net/dsa/tag_brcm.c:55:0: warning: macro "BRCM_EG_TC_MASK" is not used
>> [-Wunused-macros]
>> net/dsa/tag_brcm.c:35:0: warning: macro "BRCM_IG_TS_SHIFT" is not used
>> [-Wunused-macros]
>> net/dsa/tag_brcm.c:46:0: warning: macro "BRCM_EG_RC_MASK" is not used
>> [-Wunused-macros]
>> net/dsa/tag_brcm.c:49:0: warning: macro "BRCM_EG_RC_PROT_SNOOP" is not
>> used [-Wunused-macros]
>> net/dsa/tag_brcm.c:34:0: warning: macro "BRCM_IG_TE_MASK" is not used
>> [-Wunused-macros]
>> net/dsa/tag_brcm.c:43:0: warning: macro "BRCM_EG_CID_MASK" is not used
>> [-Wunused-macros]
>> net/dsa/tag_brcm.c:50:0: warning: macro "BRCM_EG_RC_PROT_TERM" is not
>> used [-Wunused-macros]
>> net/dsa/tag_brcm.c:54:0: warning: macro "BRCM_EG_TC_SHIFT" is not used
>> [-Wunused-macros]
>> net/dsa/tag_brcm.c:52:0: warning: macro "BRCM_EG_RC_MAC_LEARN" is not
>> used [-Wunused-macros]
>> net/dsa/tag_brcm.c:48:0: warning: macro "BRCM_EG_RC_EXCEPTION" is not
>> used [-Wunused-macros]
>>
>> Signed-off-by: Alex Shi <alex.shi@...ux.alibaba.com>
>> Cc: Andrew Lunn <andrew@...n.ch> 
>> Cc: Vivien Didelot <vivien.didelot@...il.com> 
>> Cc: Florian Fainelli <f.fainelli@...il.com> 
>> Cc: Vladimir Oltean <olteanv@...il.com> 
>> Cc: "David S. Miller" <davem@...emloft.net> 
>> Cc: Jakub Kicinski <kuba@...nel.org> 
>> Cc: netdev@...r.kernel.org 
>> Cc: linux-kernel@...r.kernel.org 
>> ---
>>  net/dsa/tag_brcm.c | 15 ---------------
>>  1 file changed, 15 deletions(-)
>>
>> diff --git a/net/dsa/tag_brcm.c b/net/dsa/tag_brcm.c
>> index e934dace3922..ce23b5d4c6b8 100644
>> --- a/net/dsa/tag_brcm.c
>> +++ b/net/dsa/tag_brcm.c
>> @@ -30,29 +30,14 @@
>>  /* 1st byte in the tag */
>>  #define BRCM_IG_TC_SHIFT	2
>>  #define BRCM_IG_TC_MASK		0x7
>> -/* 2nd byte in the tag */
>> -#define BRCM_IG_TE_MASK		0x3
>> -#define BRCM_IG_TS_SHIFT	7
>>  /* 3rd byte in the tag */
>>  #define BRCM_IG_DSTMAP2_MASK	1
>>  #define BRCM_IG_DSTMAP1_MASK	0xff
> 
> Hi Alex
> 
> It is good to remember that there are multiple readers of source
> files. There is the compiler which generates code from it, and there
> is the human trying to understand what is going on, what the hardware
> can do, how we could maybe extend the code in the future to make use
> of bits are currently don't, etc.
> 
> The compiler has no use of these macros, at the moment. But i as a
> human do. It is valuable documentation, given that there is no open
> datasheet for this hardware.
> 
> I would say these warnings are bogus, and the code should be left
> alone.

Agreed, these definitions are intended to document what the hardware
does. These warnings are getting too far.
-- 
Florian