GIT: unionfs2-2.6.27.y: i2c: Fix probing of FSC hardware monitoring chips

[Erez Zadok]

commit ba1531fcc11249827750298495c27e34f869b629
Author: Jean Delvare <khali at linux-fr.org>
Date:   Tue May 4 11:09:28 2010 +0200

    i2c: Fix probing of FSC hardware monitoring chips
    
    commit b1d4b390ea4bb480e65974ce522a04022608a8df upstream.
    
    Some FSC hardware monitoring chips (Syleus at least) doesn't like
    quick writes we typically use to probe for I2C chips. Use a regular
    byte read instead for the address they live at (0x73). These are the
    only known chips living at this address on PC systems.
    
    For clarity, this fix should not be needed for kernels 2.6.30 and
    later, as we started instantiating the hwmon devices explicitly based
    on DMI data. Still, this fix is valuable in the following two cases:
    * Support for recent FSC chips on older kernels. The DMI-based device
      instantiation is more difficult to backport than the device support
      itself.
    * Case where the DMI-based device instantiation fails, whatever the
      reason. We fall back to probing in that case, so it should work.
    
    This fixes kernel bug #15634:
    https://bugzilla.kernel.org/show_bug.cgi?id=15634
    
    Signed-off-by: Jean Delvare <khali at linux-fr.org>
    Acked-by: Hans de Goede <hdegoede at redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh at suse.de>

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 3d3fb00..5ba06d9 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -1269,14 +1269,24 @@ static int i2c_detect_address(struct i2c_client *temp_client, int kind,
 
 	/* Make sure there is something at this address, unless forced */
 	if (kind < 0) {
-		if (i2c_smbus_xfer(adapter, addr, 0, 0, 0,
-				   I2C_SMBUS_QUICK, NULL) < 0)
-			return 0;
+		if (addr == 0x73 && (adapter->class & I2C_CLASS_HWMON)) {
+			/* Special probe for FSC hwmon chips */
+			union i2c_smbus_data dummy;
 
-		/* prevent 24RF08 corruption */
-		if ((addr & ~0x0f) == 0x50)
-			i2c_smbus_xfer(adapter, addr, 0, 0, 0,
-				       I2C_SMBUS_QUICK, NULL);
+			if (i2c_smbus_xfer(adapter, addr, 0, I2C_SMBUS_READ, 0,
+					   I2C_SMBUS_BYTE_DATA, &dummy) < 0)
+				return 0;
+		} else {
+			if (i2c_smbus_xfer(adapter, addr, 0, I2C_SMBUS_WRITE, 0,
+					   I2C_SMBUS_QUICK, NULL) < 0)
+				return 0;
+
+			/* Prevent 24RF08 corruption */
+			if ((addr & ~0x0f) == 0x50)
+				i2c_smbus_xfer(adapter, addr, 0,
+					       I2C_SMBUS_WRITE, 0,
+					       I2C_SMBUS_QUICK, NULL);
+		}
 	}
 
 	/* Finally call the custom detection function */