i2c: piix4: Register SPDs

The piix4 I2C bus can carry SPDs, register them if present.
Only look on bus 0, as this is where the SPDs seem to be located.

Only the first 8 slots are supported. If the system has more,
then these will not be visible.

The AUX bus can not be probed as on some platforms it reports all
devices present and all reads return "0".
This would allow the ee1004 to be probed incorrectly.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>

drivers/i2c/busses/Kconfig

@@ -196,6 +196,7 @@ config I2C_ISMT
 config I2C_PIIX4
 	tristate "Intel PIIX4 and compatible (ATI/AMD/Serverworks/Broadcom/SMSC)"
 	depends on PCI && HAS_IOPORT
+	select I2C_SMBUS
 	help
 	  If you say yes to this option, support will be included for the Intel
 	  PIIX4 family of mainboard I2C interfaces.  Specifically, the following

drivers/i2c/busses/i2c-piix4.c

@@ -29,6 +29,7 @@
 #include <linux/stddef.h>
 #include <linux/ioport.h>
 #include <linux/i2c.h>
+#include <linux/i2c-smbus.h>
 #include <linux/slab.h>
 #include <linux/dmi.h>
 #include <linux/acpi.h>
@@ -982,6 +983,14 @@ static int piix4_add_adapter(struct pci_dev *dev, unsigned short smba,
 		return retval;
 	}
 
+	/*
+	 * The AUX bus can not be probed as on some platforms it reports all
+	 * devices present and all reads return "0".
+	 * This would allow the ee1004 to be probed incorrectly.
+	 */
+	if (port == 0)
+		i2c_register_spd(adap);
+
 	*padap = adap;
 	return 0;
 }