linux-kernel - Re: [RFC net-next 0/8] Introducing subdev bus and devlink extension

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Message-ID: <c9afecb5-3c0e-6421-ea58-b041d8173636@huawei.com>
Date:   Fri, 4 Jun 2021 09:18:04 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     moyufeng <moyufeng@...wei.com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Parav Pandit <parav@...lanox.com>,
        Or Gerlitz <gerlitz.or@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "michal.lkml@...kovi.net" <michal.lkml@...kovi.net>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Jiri Pirko <jiri@...lanox.com>,
        Salil Mehta <salil.mehta@...wei.com>,
        "lipeng (Y)" <lipeng321@...wei.com>,
        Guangbin Huang <huangguangbin2@...wei.com>,
        <shenjian15@...wei.com>, "chenhao (DY)" <chenhao288@...ilicon.com>,
        Jiaran Zhang <zhangjiaran@...wei.com>
Subject: Re: [RFC net-next 0/8] Introducing subdev bus and devlink extension

On 2021/6/4 1:53, Jakub Kicinski wrote:
> On Thu, 3 Jun 2021 11:46:43 +0800 Yunsheng Lin wrote:
>>>> can devlink port be used to indicate different PF in the same ASIC,
>>>> which already has the bus identifiers in it? It seems we need a
>>>> extra identifier to indicate the ASIC?
>>>>
>>>> $ devlink port show
>>>> ...
>>>> pci/0000:03:00.0/61: type eth netdev sw1p1s0 split_group 0  
>>>
>>> Ports can obviously be used, but which PCI device will you use to
>>> register the devlink instance? Perhaps using just one doesn't matter 
>>> if there is only one NIC in the system, but may be confusing with
>>> multiple NICs, no?  
>>
>> Yes, it is confusing, how about using the controler_id to indicate
>> different NIC? we can make sure controler_id is unqiue in the same
>> host, a controler_id corresponds to a devlink instance, vendor info
>> or serial num for the devlink instance can further indicate more info
>> to the system user?
>>
>> pci/controler_id/0000:03:00.0/61
> 
> What is a "controller id" in concrete terms? Another abstract ID which
> may change on every boot?

My initial thinking is a id from a global IDA pool, which indeed may
change on every boot.

I am not really thinking much deeper about the controller id, just
mirroring the bus identifiers for pcie device and ifindex for netdev,
which may change too if the device is pluged into different pci slot
on every boot?

> 
>>>> Does it make sense if the PF first probed creates a auxiliary device,
>>>> and the auxiliary device driver creates the devlink instance? And
>>>> the PF probed later can connect/register to that devlink instance?  
>>>
>>> I would say no, that just adds another layer of complication and
>>> doesn't link the functions in any way.  
>>
>> How about:
>> The PF first probed creates the devlink instance? PF probed later can
>> connect/register to that devlink instance created by the PF first probed.
>> It seems some locking need to ensure the above happens as intended too.
>>
>> About linking, the PF provide vendor info/serial number(or whatever is
>> unqiue between different vendor) of a controller it belong to, if the
>> controller does not exist yet, create one and connect/register to that
>> devlink instance, otherwise just do the connecting/registering.
> 
> Sounds about right, but I don't understand why another ID is
> necessary. Why not allow devlink instances to have multiple names, 
> like we allow aliases for netdevs these days?

We could still allow devlink instances to have multiple names,
which seems to be more like devlink tool problem?

For example, devlink tool could use the id or the vendor_info/
serial_number to indicate a devlink instance according to user's
request.

Aliase could be allowed too as long as devlink core provide a
field and ops to set/get the field mirroring the ifalias for
netdevice?

> 
> .
>