netdev - Re: [PATCH net-next v2 04/14] dibs: Register smc as dibs

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Message-ID: <f785ff05-acfd-4544-84b8-39f0c2d8e5ee@linux.ibm.com>
Date: Tue, 16 Sep 2025 10:37:21 +0200
From: Alexandra Winter <wintera@...ux.ibm.com>
To: Paolo Abeni <pabeni@...hat.com>, "D. Wythe" <alibuda@...ux.alibaba.com>,
        Dust Li <dust.li@...ux.alibaba.com>,
        Sidraya Jayagond
 <sidraya@...ux.ibm.com>,
        Wenjia Zhang <wenjia@...ux.ibm.com>,
        David Miller <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Andrew Lunn <andrew+netdev@...n.ch>
Cc: Julian Ruess <julianr@...ux.ibm.com>,
        Aswin Karuvally <aswin@...ux.ibm.com>,
        Halil Pasic <pasic@...ux.ibm.com>,
        Mahanta Jambigi <mjambigi@...ux.ibm.com>,
        Tony Lu
 <tonylu@...ux.alibaba.com>, Wen Gu <guwen@...ux.alibaba.com>,
        linux-rdma@...r.kernel.org, netdev@...r.kernel.org,
        linux-s390@...r.kernel.org, Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev
 <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>, Simon Horman <horms@...nel.org>,
        Eric Biggers <ebiggers@...nel.org>, Ard Biesheuvel <ardb@...nel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Harald Freudenberger <freude@...ux.ibm.com>,
        Konstantin Shkolnyy <kshk@...ux.ibm.com>
Subject: Re: [PATCH net-next v2 04/14] dibs: Register smc as dibs_client



On 16.09.25 09:40, Paolo Abeni wrote:
> On 9/11/25 9:48 PM, Alexandra Winter wrote:
>> diff --git a/net/smc/Kconfig b/net/smc/Kconfig
>> index ba5e6a2dd2fd..40dd60c1d23f 100644
>> --- a/net/smc/Kconfig
>> +++ b/net/smc/Kconfig
>> @@ -1,7 +1,7 @@
>>  # SPDX-License-Identifier: GPL-2.0-only
>>  config SMC
>>  	tristate "SMC socket protocol family"
>> -	depends on INET && INFINIBAND
>> +	depends on INET && INFINIBAND && DIBS
>>  	depends on m || ISM != m
>>  	help
>>  	  SMC-R provides a "sockets over RDMA" solution making use of
> 
> DIBS is tristate, and it looks like SMC build will fail with SMC=y and
> DIBS=m. I *think* you additionally need something alike:
> 
> 	depends on m || DIBS != m
> 	
> /P
> 


My understanding of 'SMC depends on DIBS' is that DIBS has to have
a higher or equal state than SMC (with y > m > n).

When I do 'make menuconfig' and set DIBS=m, it will only offer SMC: m|n

When I manually set DIBS=m and SMC=y, 'make oldconfig' will change that to
DIBS=m and SMC=m.

So I my understanding is: it is ok like it is. Am I missing something?

Ugly constructs like  'SMC depends on m || ISM != m' are only required for scenarios,
where SMC=y ISM=n is allowed, but SMC=y ISM=m is not allowed.
Link: https://lore.kernel.org/netdev/20231006125847.1517840-1-gbayer@linux.ibm.com/

This was actually my initial motivation for the DIBS shim layer: to get rid of the
dependencies and IFCONFIGS between ISM and SMC.