linux-kernel - Re: [PATCH net-next v3 2/2] net: mdio: mdio-i2c: Add support for single-byte SMBus operations

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Message-ID: <20250321190237.0a98e8b7@fedora.home>
Date: Fri, 21 Mar 2025 19:02:37 +0100
From: Maxime Chevallier <maxime.chevallier@...tlin.com>
To: Paolo Abeni <pabeni@...hat.com>
Cc: davem@...emloft.net, Andrew Lunn <andrew@...n.ch>, Jakub Kicinski
 <kuba@...nel.org>, Eric Dumazet <edumazet@...gle.com>, Russell King
 <linux@...linux.org.uk>, Heiner Kallweit <hkallweit1@...il.com>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 thomas.petazzoni@...tlin.com, Florian Fainelli <f.fainelli@...il.com>,
 Köry Maincent <kory.maincent@...tlin.com>, Simon Horman
 <horms@...nel.org>, Romain Gantois <romain.gantois@...tlin.com>, Antoine
 Tenart <atenart@...nel.org>, Marek Behún <kabel@...nel.org>,
 Sean Anderson <sean.anderson@...ux.dev>, Bjørn Mork
 <bjorn@...k.no>
Subject: Re: [PATCH net-next v3 2/2] net: mdio: mdio-i2c: Add support for
 single-byte SMBus operations

On Fri, 21 Mar 2025 18:53:51 +0100
Paolo Abeni <pabeni@...hat.com> wrote:

> On 3/14/25 5:23 PM, Maxime Chevallier wrote:
> > diff --git a/drivers/net/mdio/mdio-i2c.c b/drivers/net/mdio/mdio-i2c.c
> > index da2001ea1f99..202f486e71f1 100644
> > --- a/drivers/net/mdio/mdio-i2c.c
> > +++ b/drivers/net/mdio/mdio-i2c.c
> > @@ -106,6 +106,62 @@ static int i2c_mii_write_default_c22(struct mii_bus *bus, int phy_id, int reg,
> >  	return i2c_mii_write_default_c45(bus, phy_id, -1, reg, val);
> >  }
> >  
> > +static int smbus_byte_mii_read_default_c22(struct mii_bus *bus, int phy_id,
> > +					   int reg)
> > +{
> > +	struct i2c_adapter *i2c = bus->priv;
> > +	union i2c_smbus_data smbus_data;
> > +	int val = 0, ret;
> > +
> > +	if (!i2c_mii_valid_phy_id(phy_id))
> > +		return 0;
> > +
> > +	ret = i2c_smbus_xfer(i2c, i2c_mii_phy_addr(phy_id), 0,
> > +			     I2C_SMBUS_READ, reg,
> > +			     I2C_SMBUS_BYTE_DATA, &smbus_data);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	val = ((smbus_data.byte & 0xff) << 8);  
> 
> External brackets not needed.
> 
> > +
> > +	ret = i2c_smbus_xfer(i2c, i2c_mii_phy_addr(phy_id), 0,
> > +			     I2C_SMBUS_READ, reg,
> > +			     I2C_SMBUS_BYTE_DATA, &smbus_data);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	val |= (smbus_data.byte & 0xff);  
> 
> same here.
> 
> > +
> > +	return val;
> > +}
> > +
> > +static int smbus_byte_mii_write_default_c22(struct mii_bus *bus, int phy_id,
> > +					    int reg, u16 val)
> > +{
> > +	struct i2c_adapter *i2c = bus->priv;
> > +	union i2c_smbus_data smbus_data;
> > +	int ret;
> > +
> > +	if (!i2c_mii_valid_phy_id(phy_id))
> > +		return 0;
> > +
> > +	smbus_data.byte = ((val & 0xff00) >> 8);  
> 
> and here.
> 
> > +
> > +	ret = i2c_smbus_xfer(i2c, i2c_mii_phy_addr(phy_id), 0,
> > +			     I2C_SMBUS_WRITE, reg,
> > +			     I2C_SMBUS_BYTE_DATA, &smbus_data);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	smbus_data.byte = val & 0xff;  
> 
> I would not have noted the above if even this one carried additional
> brackets...

:( You're correct, sorry not to have spotted that before... I'll fix
this for v4.

Maxime