[PATCH v2] i2c: smbus: Prepare i2c_register_spd for usage on muxed segments

[Heiner Kallweit <hkallweit1@gmail.com>]

If this is an adapter on a muxed bus segment, assume that each segment
is connected to a subset of the (> 8) overall memory slots. In this
case let's probe the maximum of 8 slots, however stop if the number
of overall populated slots is reached.

If we're not on a muxed segment and the total number of slots is > 8,
then warn because then not all SPD eeproms can be addressed.
Presumably the bus is muxed, but the mux config is missing.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
v2:
- Make comments / messages more descriptive
- Remove second patch of the series to ask for testing on lkml
- change dev_err to dev_warn
---
 drivers/i2c/i2c-smbus.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/drivers/i2c/i2c-smbus.c b/drivers/i2c/i2c-smbus.c
index 74807c6db..c45d09782 100644
--- a/drivers/i2c/i2c-smbus.c
+++ b/drivers/i2c/i2c-smbus.c
@@ -351,13 +351,20 @@ void i2c_register_spd(struct i2c_adapter *adap)
 	if (!dimm_count)
 		return;
 
-	dev_info(&adap->dev, "%d/%d memory slots populated (from DMI)\n",
-		 dimm_count, slot_count);
-
-	if (slot_count > 8) {
-		dev_warn(&adap->dev,
-			 "Systems with more than 8 memory slots not supported yet, not instantiating SPD\n");
-		return;
+	/*
+	 * If we're a child adapter on a muxed segment, then limit slots to 8,
+	 * as this is the max number of SPD EEPROMs that can be addressed per bus.
+	 */
+	if (i2c_parent_is_i2c_adapter(adap)) {
+		slot_count = 8;
+	} else {
+		if (slot_count > 8) {
+			dev_warn(&adap->dev,
+				 "More than 8 memory slots on a single bus, contact i801 maintainer to add missing mux config\n");
+			return;
+		}
+		dev_info(&adap->dev, "%d/%d memory slots populated (from DMI)\n",
+			 dimm_count, slot_count);
 	}
 
 	/*
-- 
2.44.0