Detect SPD Write Disable in SMBHSTCFG and expose it through
I2C adapter quirk. The I2C client driver may decide whether
SPD write operations are supported without implementing
device-specific policies in the SMBus controller driver.

Signed-off-by: Tinsae Tadesse <tinsaetadesse2015@gmail.com>
---
 drivers/i2c/busses/i2c-i801.c | 16 +++++++++++++++-
 include/linux/i2c.h           |  3 +++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index 9e1789725edf..d771e9f5f82f 100644
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -1533,6 +1533,11 @@ static int i801_probe(struct pci_dev *dev, const struct pci_device_id *id)
 {
 	int err, i, bar = SMBBAR;
 	struct i801_priv *priv;
+	struct i2c_adapter_quirks *quirks;
+
+	quirks = devm_kzalloc(&dev->dev, sizeof(*quirks), GFP_KERNEL);
+	if (!quirks)
+		return -ENOMEM;
 
 	priv = devm_kzalloc(&dev->dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
@@ -1600,8 +1605,17 @@ static int i801_probe(struct pci_dev *dev, const struct pci_device_id *id)
 		/* Disable SMBus interrupt feature if SMBus using SMI# */
 		priv->features &= ~FEATURE_IRQ;
 	}
-	if (priv->original_hstcfg & SMBHSTCFG_SPD_WD)
+
+	/*
+	 * Detect the SPD Write Disabled status. Mark the adapter
+	 * as unable to perform SPD writes, which allows consuming
+	 * drivers to decide on safe operation.
+	 */
+	if (priv->original_hstcfg & SMBHSTCFG_SPD_WD) {
 		pci_info(dev, "SPD Write Disable is set\n");
+		quirks->flags |= I2C_AQ_SPD_WRITE_DISABLED;
+	}
+	priv->adapter.quirks = quirks;
 
 	/* Clear special mode bits */
 	if (priv->features & (FEATURE_SMBUS_PEC | FEATURE_BLOCK_BUFFER))
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 20fd41b51d5c..4b89f0bf62a1 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -726,6 +726,9 @@ struct i2c_adapter_quirks {
 /* adapter cannot do repeated START */
 #define I2C_AQ_NO_REP_START		BIT(7)
 
+/* SPD writes are blocked by host controller */
+#define I2C_AQ_SPD_WRITE_DISABLED	BIT(8)
+
 /*
  * i2c_adapter is the structure used to identify a physical i2c bus along
  * with the access algorithms necessary to access it.
-- 
2.52.0