netdev - Re: [PATCH net-next v4 1/4] net: phy: mdio-i2c: support I2C MDIO protocol for RollBall SFP modules

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Message-ID: <20210112220114.0f990cbe@kernel.org>
Date:   Tue, 12 Jan 2021 22:01:14 +0100
From:   Marek Behún <kabel@...nel.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org, Russell King <rmk+kernel@...linux.org.uk>,
        Jakub Kicinski <kuba@...nel.org>, davem@...emloft.net,
        pali@...nel.org
Subject: Re: [PATCH net-next v4 1/4] net: phy: mdio-i2c: support I2C MDIO
 protocol for RollBall SFP modules

On Tue, 12 Jan 2021 21:54:24 +0100
Andrew Lunn <andrew@...n.ch> wrote:

> > +static int i2c_transfer_rollball(struct i2c_adapter *i2c,
> > +				 struct i2c_msg *msgs, int num)
> > +{
> > +	u8 saved_page;
> > +	int ret;
> > +
> > +	i2c_lock_bus(i2c, I2C_LOCK_SEGMENT);
> > +
> > +	/* save original page */
> > +	ret = __i2c_rollball_get_page(i2c, msgs->addr, &saved_page);
> > +	if (ret)
> > +		goto unlock;
> > +
> > +	/* change to RollBall MDIO page */
> > +	ret = __i2c_rollball_set_page(i2c, msgs->addr, SFP_PAGE_ROLLBALL_MDIO);
> > +	if (ret)
> > +		goto unlock;
> > +
> > +	/* do the transfer */
> > +	ret = __i2c_transfer_err(i2c, msgs, num);
> > +	if (ret)
> > +		goto unlock;  
> 
> If get page and set page worked, and you get an error in during the
> actual data transfer, i wonder if you should try restoring the page
> before returning with the error?

I don't know. Can i2c trasfer fail and the next one succeed?