netdev - Re: [PATCH net-next 7/8] net: switchdev: Replace port attr set SDO with a notification

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Date:   Mon, 25 Feb 2019 11:47:12 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Ido Schimmel <idosch@...lanox.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:STAGING SUBSYSTEM" <devel@...verdev.osuosl.org>,
        "moderated list:ETHERNET BRIDGE" <bridge@...ts.linux-foundation.org>,
        Jiri Pirko <jiri@...lanox.com>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "vivien.didelot@...il.com" <vivien.didelot@...il.com>
Subject: Re: [PATCH net-next 7/8] net: switchdev: Replace port attr set SDO
 with a notification

On 2/25/19 1:49 AM, Ido Schimmel wrote:
> On Sun, Feb 24, 2019 at 08:47:27AM -0800, Florian Fainelli wrote:
>> Le 2/23/19 à 2:32 AM, Ido Schimmel a écrit :
>>> On Fri, Feb 22, 2019 at 03:59:25PM -0800, Florian Fainelli wrote:
>>>> -	if (attr->flags & SWITCHDEV_F_NO_RECURSE)
>>>> +	if (attr & SWITCHDEV_F_DEFER)
>>>> +		rc = call_switchdev_blocking_notifiers(nt, dev,
>>>> +						       &attr_info.info, NULL);
>>>> +	else
>>>> +		rc = call_switchdev_notifiers(nt, dev, &attr_info.info, NULL);
>>>
>>> I don't believe this is needed. You're calling this function from
>>> switchdev_port_attr_set_now() which is always called from process
>>> context. switchdev_port_attr_set() takes care of that. Similar to
>>> switchdev_port_obj_add().
>>
>> Except for net/bridge/br_switchdev.c when we check the bridge port's
>> flags support with PRE_BRIDGE_FLAGS. In that case we are executing from
>> the caller (atomic) context and we can't defer otherwise that trumps the
>> whole idea of being able to do a quick check and return that to the
>> caller that we cannot support specific flags. How would you recommend
>> approaching that?
> 
> In this case you can invoke call_switchdev_notifiers() directly from
> br_switchdev_set_port_flag(). Eventually switchdev_port_attr_set() will
> be gone and bridge code will invoke the notifiers directly.

That can be done, but it still requires the target driver (mlxsw,
ocelot, dsa, etc.) to support attribute notification from blocking and
non-blocking context. Are you fine with that?
-- 
Florian