netdev - Re: [RFC PATCH 6/9] net: dsa: hellcreek: Add debugging mechanisms

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Date:   Fri, 19 Jun 2020 10:36:45 +0200
From:   Kurt Kanzenbach <kurt@...utronix.de>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Richard Cochran <richardcochran@...il.com>,
        Kamil Alkhouri <kamil.alkhouri@...offenburg.de>,
        ilias.apalodimas@...aro.org
Subject: Re: [RFC PATCH 6/9] net: dsa: hellcreek: Add debugging mechanisms

Hi Andrew,

On Thu Jun 18 2020, Andrew Lunn wrote:
> On Thu, Jun 18, 2020 at 08:40:26AM +0200, Kurt Kanzenbach wrote:
>> The switch has registers which are useful for debugging issues:
>
> debugfs is not particularly likes. Please try to find other means
> where possible. Memory usage fits nicely into devlink. See mv88e6xxx
> which exports the ATU fill for example.

OK, I'll have a look at devlink and the mv88e6xxx driver to see if that
could be utilized.

> Are trace registers counters?

No. The trace registers provide bits for error conditions and if packets
have been dropped e.g. because of full queues or FCS errors, and so on.

>
>> +static int hellcreek_debugfs_init(struct hellcreek *hellcreek)
>> +{
>> +	struct dentry *file;
>> +
>> +	hellcreek->debug_dir = debugfs_create_dir(dev_name(hellcreek->dev),
>> +						  NULL);
>> +	if (!hellcreek->debug_dir)
>> +		return -ENOMEM;
>
> Just a general comment. You should not check the return value from any
> debugfs call, since it is totally optional. It will also do the right
> thing if the previous call has failed. There are numerous emails from
> GregKH about this.

OK.

Thanks,
Kurt

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