netdev - Re: [RFC net-next 11/17] net/dibs: Move struct device to dibs

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Message-ID: <aJ9P0WpHU30zpLLt@linux.alibaba.com>
Date: Fri, 15 Aug 2025 23:18:41 +0800
From: Dust Li <dust.li@...ux.alibaba.com>
To: Alexandra Winter <wintera@...ux.ibm.com>,
	David Miller <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"D. Wythe" <alibuda@...ux.alibaba.com>,
	Sidraya Jayagond <sidraya@...ux.ibm.com>,
	Wenjia Zhang <wenjia@...ux.ibm.com>,
	Julian Ruess <julianr@...ux.ibm.com>
Cc: 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>,
	Thorsten Winkler <twinkler@...ux.ibm.com>,
	Simon Horman <horms@...nel.org>,
	Mahanta Jambigi <mjambigi@...ux.ibm.com>,
	Tony Lu <tonylu@...ux.alibaba.com>,
	Wen Gu <guwen@...ux.alibaba.com>, Halil Pasic <pasic@...ux.ibm.com>,
	linux-rdma@...r.kernel.org
Subject: Re: [RFC net-next 11/17] net/dibs: Move struct device to dibs_dev

On 2025-08-15 13:59:49, Alexandra Winter wrote:
>
>
>On 15.08.25 03:56, Dust Li wrote:
>> On 2025-08-14 10:51:27, Alexandra Winter wrote:
>>>
>>> On 06.08.25 17:41, Alexandra Winter wrote:
>>> [...]
>>>> Replace smcd->ops->get_dev(smcd) by dibs_get_dev().
>>>>
>>> Looking at the resulting code, I don't really like this concept of a *_get_dev() function,
>>> that does not call get_device().
>>> I plan to replace that by using dibs->dev directly in the next version.
>> May I ask why? Because of the function name ? If so, maybe we can change the name.
>
>Yes the name. Especially, as it is often used as argument for get_device() or put_device().
>Eventually I would like to provide dibs_get_dev()/dibs_put_dev() that actually
>do refcounting.
>And then I thought defining dibs_read_dev() is not helping readability.

I see. I don't like dibs_get_dev() either.
What about dibs_device_to_dev() or dibs_to_dev() ?

If we can't agree on a name we’re all happy with, I agree we can
leave it as is for now.


>> 
>> While I don't have a strong preference either way, I personally favor
>> hiding the members of the dibs_dev structure from the upper layer. In my
>> opinion, it would be better to avoid direct access to dibs members from
>> upper layers and instead provide dedicated interface functions.
>> 
>> For example, I even think we should not expose dibs->ops->xxx directly
>> to the SMC layer. Encapsulating such details would improve modularity
>> and maintainability. Just like what IB subsystem has done before :)
>> 
>> For example:
>> # git grep dibs net/smc
>> [...]
>> net/smc/smc_ism.c:      return dibs->ops->query_remote_gid(dibs, &ism_rgid, vlan_id ? 1 : 0,
>> net/smc/smc_ism.c:      return smcd->dibs->ops->get_fabric_id(smcd->dibs);
>> net/smc/smc_ism.c:      if (!smcd->dibs->ops->add_vlan_id)
>> net/smc/smc_ism.c:      if (smcd->dibs->ops->add_vlan_id(smcd->dibs, vlanid)) {
>> net/smc/smc_ism.c:      if (!smcd->dibs->ops->del_vlan_id)
>> net/smc/smc_ism.c:      if (smcd->dibs->ops->del_vlan_id(smcd->dibs, vlanid))
>> [...]
>> 
>> Best regards,
>> Dust
>
>
>I see your point and I remember you brought that up in your review of
>[RFC net-next 0/7] Provide an ism layer
>already.
>
>I tried to keep this series to a meaningful minimum, which is a tradeoff.
>If possible, I just wanted to move code around and add the dibs layer
>in-between. There are several areas where I would like to see even more
>de-coupling. eg.:
>- handle_irq(): Clients should not run in interrupt context,
>  a receive_data() callback function would be better.
>- The device drivers should not loop through the client array
>- dibs_dev_op.*_dmb() functions reveal unnecessary details of the
>  internal dmb struct to the clients
>- ...
>
>So instead of adding a set of 1:1 caller functions / interface functions
>for dibs_dev_ops and dibs_client_ops now, I would like to propose to work
>on further decoupling devices and clients by adding more abstractions that
>bring benefit. And then replace the remaining calls to ops by 1:1 caller
>functions. Does that make sense? Or does anybody feel strongly that I need
>to provide interface functions now?

Yes, I agree we can do that in the future.

Best regards,
Dust