netdev - Re: [PATCH net-next 5/6] net: dsa: realtek-smi: add rtl8365mb subdriver for RTL8365MB-VC

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Message-ID: <20211013081340.0ca97db1@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 13 Oct 2021 08:13:40 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Alvin Šipraga <ALSI@...g-olufsen.dk>
Cc:     Alvin Šipraga <alvin@...s.dk>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh+dt@...nel.org>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Michael Rasmussen <MIR@...g-olufsen.dk>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 5/6] net: dsa: realtek-smi: add rtl8365mb
 subdriver for RTL8365MB-VC

On Wed, 13 Oct 2021 08:33:36 +0000 Alvin Šipraga wrote:
> On 10/12/21 5:27 PM, Jakub Kicinski wrote:
> > On Tue, 12 Oct 2021 14:35:54 +0200 Alvin Šipraga wrote:  
> >> +	{ 0, 4, 2, "dot3StatsFCSErrors" },
> >> +	{ 0, 6, 2, "dot3StatsSymbolErrors" },
> >> +	{ 0, 8, 2, "dot3InPauseFrames" },
> >> +	{ 0, 10, 2, "dot3ControlInUnknownOpcodes" },  
> > ...
> > 
> > You must expose counters via existing standard APIs.
> > 
> > You should implement these ethtool ops:  
> 
> I implement the dsa_switch_ops callback .get_ethtool_stats, using an 
> existing function rtl8366_get_ethtool_stats in the switch helper library 
> rtl8366.c. It was my understanding that this is the correct way to 
> expose counters within the DSA framework - please correct me if that is 
> wrong.

It's the legacy way, today we have a unified API for reporting those
stats so user space SW doesn't have to maintain a myriad string matches
to get to basic IEEE stats across vendors. Driver authors have a truly
incredible ability to invent their own names for standard stats. It
appears that your pick of names is also unique :)

It should be trivial to plumb the relevant ethtool_ops thru to
dsa_switch_ops if relevant dsa ops don't exist.

You should also populate correct stats in dsa_switch_ops::get_stats64
(see the large comment above the definition of struct
rtnl_link_stats64 for mapping). A word of warning there, tho, that
callback runs in an atomic context so if your driver needs to block it
has to read the stats periodically from a async work.

> The structure you highlight is just some internal glue to sort out the 
> internal register mapping. I borrowed the approach from the existing 
> rtl8366rb.c Realtek SMI subdriver.

The callbacks listed below are relatively new, they may have not
existed when that driver was written. Also I may have missed it 
in review. 

> > 	void	(*get_eth_phy_stats)(struct net_device *dev,
> > 				     struct ethtool_eth_phy_stats *phy_stats);
> > 	void	(*get_eth_mac_stats)(struct net_device *dev,
> > 				     struct ethtool_eth_mac_stats *mac_stats);
> > 	void	(*get_eth_ctrl_stats)(struct net_device *dev,
> > 				      struct ethtool_eth_ctrl_stats *ctrl_stats);
> > 	void	(*get_rmon_stats)(struct net_device *dev,
> > 				  struct ethtool_rmon_stats *rmon_stats,
> > 				  const struct ethtool_rmon_hist_range **ranges);