linux-kernel - Re: [PATCH net-next v3 2/9] net: dsa: microchip: ksz8795: add phylink support

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Date:   Thu, 10 Jun 2021 12:20:10 +0200
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Woojung Huh <woojung.huh@...rochip.com>,
        UNGLinuxDriver@...rochip.com, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Michael Grzeschik <m.grzeschik@...gutronix.de>,
        kernel@...gutronix.de, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Russell King <linux@...linux.org.uk>
Subject: Re: [PATCH net-next v3 2/9] net: dsa: microchip: ksz8795: add
 phylink support

On Thu, May 27, 2021 at 01:13:04AM +0300, Vladimir Oltean wrote:
> On Wed, May 26, 2021 at 06:30:30AM +0200, Oleksij Rempel wrote:
> > From: Michael Grzeschik <m.grzeschik@...gutronix.de>
> > 
> > This patch adds the phylink support to the ksz8795 driver to provide
> > configuration exceptions on quirky KSZ8863 and KSZ8873 ports.
> > 
> > Signed-off-by: Michael Grzeschik <m.grzeschik@...gutronix.de>
> > Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> > ---
> >  drivers/net/dsa/microchip/ksz8795.c | 59 +++++++++++++++++++++++++++++
> >  1 file changed, 59 insertions(+)
> > 
> > diff --git a/drivers/net/dsa/microchip/ksz8795.c b/drivers/net/dsa/microchip/ksz8795.c
> > index ba065003623f..cf81ae87544d 100644
> > --- a/drivers/net/dsa/microchip/ksz8795.c
> > +++ b/drivers/net/dsa/microchip/ksz8795.c
> > @@ -18,6 +18,7 @@
> >  #include <linux/micrel_phy.h>
> >  #include <net/dsa.h>
> >  #include <net/switchdev.h>
> > +#include <linux/phylink.h>
> >  
> >  #include "ksz_common.h"
> >  #include "ksz8795_reg.h"
> > @@ -1420,11 +1421,69 @@ static int ksz8_setup(struct dsa_switch *ds)
> >  	return 0;
> >  }
> >  
> > +static void ksz8_validate(struct dsa_switch *ds, int port,
> > +			  unsigned long *supported,
> > +			  struct phylink_link_state *state)
> > +{
> > +	__ETHTOOL_DECLARE_LINK_MODE_MASK(mask) = { 0, };
> > +	struct ksz_device *dev = ds->priv;
> > +
> > +	if (port == dev->cpu_port) {
> > +		if (state->interface != PHY_INTERFACE_MODE_RMII &&
> > +		    state->interface != PHY_INTERFACE_MODE_MII &&
> > +		    state->interface != PHY_INTERFACE_MODE_NA)
> > +			goto unsupported;
> > +	} else if (port > dev->port_cnt) {
> > +		bitmap_zero(supported, __ETHTOOL_LINK_MODE_MASK_NBITS);
> > +		dev_err(ds->dev, "Unsupported port: %i\n", port);
> > +		return;
> 
> Is this possible or do we just like to invent things to check?
> Unless I'm missing something, ksz8_switch_init() does:
> 
> 	dev->ds->num_ports = dev->port_cnt;
> 
> and dsa_port_phylink_validate() does:
> 
> 	ds->ops->phylink_validate(ds, dp->index, supported, state);
> 
> where dp->index is set to @port by dsa_port_touch() in this loop:
> 
> 	for (port = 0; port < ds->num_ports; port++) {
> 		dp = dsa_port_touch(ds, port);
> 		if (!dp)
> 			return -ENOMEM;
> 	}
> 
> So, if 0 <= dp->index < ds->num_ports == dev->port_cnt, what is the point?

good point

Regards,
Oleksij
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