netdev - Re: [PATCH net-next] net: dsa: felix: suppress -EPROBE

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Date:   Thu, 07 Apr 2022 16:04:20 +0200
From:   Michael Walle <michael@...le.cc>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, UNGLinuxDriver@...rochip.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] net: dsa: felix: suppress -EPROBE_DEFER errors

Am 2022-04-07 15:56, schrieb Vladimir Oltean:
> On Thu, Apr 07, 2022 at 03:06:25PM +0200, Michael Walle wrote:
>> Due to missing prerequisites the probe of the felix switch might be
>> deferred:
>> [    4.435305] mscc_felix 0000:00:00.5: Failed to register DSA switch: 
>> -517
>> 
>> It's not an error. Use dev_err_probe() to demote the error to a debug
>> message. While at it, replace all the dev_err()'s in the probe with
>> dev_err_probe().
>> 
>> Signed-off-by: Michael Walle <michael@...le.cc>
>> ---
> 
> Please limit the dev_err_probe() to dsa_register_switch(). The resource
> that is missing is the DSA master, see of_find_net_device_by_node().
> The others cannot possibly return -EPROBE_DEFER.

This was my rationale (from the function doc):

  * Note that it is deemed acceptable to use this function for error
  * prints during probe even if the @err is known to never be 
-EPROBE_DEFER.
  * The benefit compared to a normal dev_err() is the standardized format
  * of the error code and the fact that the error code is returned.

In any case I don't have a strong opinion.

>> 
>> Should this be a patch with a Fixes tag?
> 
> Whichever way you wish, no preference.

I'll limit it to just the one dev_err() and add a Fixes,
there might be scripts out there who greps dmesg for errors.

-michael