Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 9 Apr 2024 09:44:44 +0800 | Subject | Re: [RFC PATCH net-next v5 04/11] net/smc: implement some unsupported operations of loopback-ism | From | Wen Gu <> |
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On 2024/4/4 23:15, Niklas Schnelle wrote: > On Thu, 2024-04-04 at 21:12 +0800, Wen Gu wrote: >> >> On 2024/4/4 19:42, Niklas Schnelle wrote: >>> On Thu, 2024-04-04 at 17:32 +0800, Wen Gu wrote: >>>> >>>> On 2024/4/4 00:25, Gerd Bayer wrote: >>>>> On Sun, 2024-03-24 at 21:55 +0800, Wen Gu wrote: >>>>>> This implements some operations that loopback-ism does not support >>>>>> currently: >>>>>> - vlan operations, since there is no strong use-case for it. >>>>>> - signal_event operations, since there is no event to be processed >>>>>> by the loopback-ism device. >>>>> >>>>> Hi Wen, >>>>> >>>>> I wonder if the these operations that are not supported by loopback-ism >>>>> should rather be marked "optional" in the struct smcd_ops, and the >>>>> calling code should call these only when they are implemented. >>>>> >>>>> Of course this would mean more changes to net/smc/smc_core.c - but >>>>> loopback-ism could omit these "boiler-plate" functions. >>>>> >>>> >>>> Hi Gerd. >>>> >>>> Thank you for the thoughts! I agree that checks like 'if(smcd->ops->xxx)' >>>> can avoid the device driver from implementing unsupported operations. But I >>>> am afraid that which operations need to be defined as 'optional' may differ >>>> from different device perspectives (e.g. for loopback-ism they are vlan-related >>>> opts and signal_event). So I perfer to simply let the smc protocol assume >>>> that all operations have been implemented, and let drivers to decide which >>>> ones are unsupported in implementation. What do you think? >>>> >>>> Thanks! >>>> >>> >>> I agree with Gerd, in my opinion it is better to document ops as >>> optional and then allow their function pointers to be NULL and check >>> for that. Acting like they are supported and then they turn out to be >>> nops to me seems to contradict the principle of least surprises. I also >>> think we can find a subset of mandatory ops without which SMC-D is >>> impossible and then everything else should be optional. >> >> I see. If we all agree to classify smcd_ops into mandatory and optional ones, >> I'll add a patch to mark the optional ops and check if they are implemented. > > Keep in mind I don't speak for the SMC maintainers but that does sound > reasonable to me. >
Hi Wenjia and Jan, do you have any comments on this and [1]? Thanks!
[1] https://lore.kernel.org/netdev/60b4aec0b4bf4474d651b653c86c280dafc4518a.camel@linux.ibm.com/
>> >>> >>> As a first guess I think the following options may be mandatory: >>> >>> * query_remote_gid() >>> * register_dmb()/unregister_dmb() >>> * move_data() >>> For this one could argue that either move_data() or >>> attach_dmb()/detach_dmb() is required though personally I would >>> prefer to always have move_data() as a fallback and simple API >>> * supports_v2() >>> * get_local_gid() >>> * get_chid() >>> * get_dev() >> I agree with this classification. Just one point, maybe we can take >> supports_v2() as an optional ops, like support_dmb_nocopy()? e.g. if >> it is not implemented, we treat it as an ISMv1. >> >> Thanks! > > Interpreting a NULL supports_v2() as not supporting v2 sounds > reasonable to me.
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