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: <X/4MgF+n+jQZ11Gd@lunn.ch>
Date:   Tue, 12 Jan 2021 21:54:24 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Marek Behún <kabel@...nel.org>
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

> +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?

> +
> +	/* restore original page */
> +	ret = __i2c_rollball_set_page(i2c, msgs->addr, saved_page);
> +
> +unlock:
> +	i2c_unlock_bus(i2c, I2C_LOCK_SEGMENT);
> +
> +	return ret;
> +}