netdev - Re: [patch net-next RFC 00/10] introduce line card support for modular switch

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Date:   Mon, 18 Jan 2021 19:39:47 -0700
From:   David Ahern <dsahern@...il.com>
To:     Edwin Peer <edwin.peer@...adcom.com>
Cc:     Jiri Pirko <jiri@...nulli.us>, netdev <netdev@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jacob Keller <jacob.e.keller@...el.com>, roopa@...dia.com,
        mlxsw <mlxsw@...dia.com>
Subject: Re: [patch net-next RFC 00/10] introduce line card support for
 modular switch

On 1/18/21 4:40 PM, Edwin Peer wrote:
> On Mon, Jan 18, 2021 at 2:57 PM David Ahern <dsahern@...il.com> wrote:
> 
>> On 1/18/21 11:01 AM, Edwin Peer wrote:
>>> I'm facing a similar issue with NIC firmware that isn't yet ready by
>>> device open time, but have been resisting the urge to lie to the stack
>>
>> why not have the ndo_open return -EBUSY or -EAGAIN to tell S/W to try
>> again 'later'?
> 
> Indeed, this is what we ended up doing, although we still need to
> confirm Network Manager, systemd and whatever else our customers might
> use do the necessary to satisfy the user requirement to handle the
> delayed init.

I am not surprised about the issue - boot times have been improved and
devices have gotten more complicated. And I was wondering how network
managers (add ifupdown{2} to that list) would handle an EAGAIN. You
could have an event sent -- e.g., IFLA_EVENT_FW_READY -- to allow
managers to avoid polling. Redundant for multiple netdev's per device,
but makes it event driven.

> 
> Only reason I piped up is that this line card thing seems to introduce
> a similar issue.

Seems reasonable.