On Tue, Jan 12, 2021 at 09:54:24PM +0100, Andrew Lunn wrote:

quoted

+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?

That's what we do with paged PHYs - if the access encounters an error,
we still attempt to restore the page and propagate the _original_ error.
We would only propagate the error from the page restore if it was the
only error.  See the logic and comments for phy_restore_page().

Note that phy_(save|select)_page()..phy_restore_page() deal with the
locking, which is why they always have to be paired (also means that
the user doesn't have to think too hard about error handling.)

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