netdev - Re: [PATCH net-next] net: dsa: felix: provide own phylink MAC operations

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Message-ID: <Zh1GvcOTXqb7CpQt@shell.armlinux.org.uk>
Date: Mon, 15 Apr 2024 16:24:45 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Vladimir Oltean <olteanv@...il.com>
Cc: Andrew Lunn <andrew@...n.ch>, Vladimir Oltean <vladimir.oltean@....com>,
	Claudiu Manoil <claudiu.manoil@....com>,
	Alexandre Belloni <alexandre.belloni@...tlin.com>,
	UNGLinuxDriver@...rochip.com,
	Florian Fainelli <f.fainelli@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Colin Foster <colin.foster@...advantage.com>,
	netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net: dsa: felix: provide own phylink MAC
 operations

On Mon, Apr 15, 2024 at 01:34:53PM +0300, Vladimir Oltean wrote:
> On Fri, Apr 12, 2024 at 04:15:08PM +0100, Russell King (Oracle) wrote:
> > Convert felix to provide its own phylink MAC operations, thus
> > avoiding the shim layer in DSA's port.c.
> > 
> > Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
> > ---
> > diff --git a/drivers/net/dsa/ocelot/ocelot_ext.c b/drivers/net/dsa/ocelot/ocelot_ext.c
> > index 22187d831c4b..a8927dc7aca4 100644
> > --- a/drivers/net/dsa/ocelot/ocelot_ext.c
> > +++ b/drivers/net/dsa/ocelot/ocelot_ext.c
> > @@ -96,6 +96,7 @@ static int ocelot_ext_probe(struct platform_device *pdev)
> >  	ds->num_tx_queues = felix->info->num_tx_queues;
> >  
> >  	ds->ops = &felix_switch_ops;
> > +	ds->phylink_mac_ops = &felix_phylink_mac_ops;
> 
> There are actually 2 more places which need this: felix_vsc9959.c,
> seville_vsc9953.c.

Looking at these three, isn't there good reason to merge the allocation
and initialisation of struct dsa_switch together in all three drivers?
All three are basically doing the same thing:

felix_vsc9959.c:
        ds->dev = &pdev->dev;
        ds->num_ports = felix->info->num_ports;
        ds->num_tx_queues = felix->info->num_tx_queues;
        ds->ops = &felix_switch_ops;
        ds->priv = ocelot;
        felix->ds = ds;

ocelot_ext.c:
        ds->dev = dev;
        ds->num_ports = felix->info->num_ports;
        ds->num_tx_queues = felix->info->num_tx_queues;
        ds->ops = &felix_switch_ops;
        ds->priv = ocelot;
        felix->ds = ds;

seville_vsc9953.c:
        ds->dev = &pdev->dev;
        ds->num_ports = felix->info->num_ports;
        ds->ops = &felix_switch_ops;
        ds->priv = ocelot;
        felix->ds = ds;

Also, I note that felix->info->num_tx_queues on seville_vsc9953.c
is set to OCELOT_NUM_TC, which is defined to be 8, and is the same
value for ocelot_ext and felix_vsc9959. Presumably this unintentionally
missing from seville_vsc9953.c... because why initialise a private
struct member to a non-zero value and then not use it.

An alternative would be to initialise .num_tx_queues in seville_vsc9953.c
to zero.

If we had common code doing this initialisation, then it wouldn't be
missed... and neither would have _this_ addition of the phylink MAC
ops missed the other two drivers - so I think that's something which
should be done as a matter of course - and thus there will be no need
to export these two data structures, just an initialisation (and
destruction) function. I don't think we would even need the destruction
function if we used devm_kzalloc().

Good idea?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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