i2c: piix4: Export i2c_piix4 driver functions as library

Export the following i2c_piix4 driver functions as a library so that the
AMD ASF driver can utilize these core functionalities from the i2c_piix4
driver:

- piix4_sb800_region_request(): Request access to a specific SMBus region
on the SB800 chipset.

- piix4_sb800_region_release(): Release the previously requested SMBus
region on the SB800 chipset.

- piix4_transaction(): Handle SMBus transactions between the SMBus
controller and connected devices.

- piix4_sb800_port_sel(): Select the appropriate SMBus port on the SB800
chipset.

By making these functions available as a library, enable the AMD ASF
driver to leverage the established mechanisms in the i2c_piix4 driver,
promoting code reuse and consistency across different drivers.

Reviewed-by: Andy Shevchenko <[e-mail]>
Co-developed-by: Sanket Goswami <[e-mail]>
Signed-off-by: Sanket Goswami <[e-mail]>
Signed-off-by: Shyam Sundar S K <[e-mail]>
Signed-off-by: Andi Shyti <[e-mail]>

drivers/i2c/busses/i2c-piix4.c

···
 	struct sb800_mmio_cfg mmio_cfg;
 };
 
-static int piix4_sb800_region_request(struct device *dev,
-				      struct sb800_mmio_cfg *mmio_cfg)
+int piix4_sb800_region_request(struct device *dev, struct sb800_mmio_cfg *mmio_cfg)
 {
 	if (mmio_cfg->use_mmio) {
 		void __iomem *addr;
···
 
 	return 0;
 }
+EXPORT_SYMBOL_NS_GPL(piix4_sb800_region_request, PIIX4_SMBUS);
 
-static void piix4_sb800_region_release(struct device *dev,
-				       struct sb800_mmio_cfg *mmio_cfg)
+void piix4_sb800_region_release(struct device *dev, struct sb800_mmio_cfg *mmio_cfg)
 {
 	if (mmio_cfg->use_mmio) {
 		iounmap(mmio_cfg->addr);
···
 
 	release_region(SB800_PIIX4_SMB_IDX, SB800_PIIX4_SMB_MAP_SIZE);
 }
+EXPORT_SYMBOL_NS_GPL(piix4_sb800_region_release, PIIX4_SMBUS);
 
 static bool piix4_sb800_use_mmio(struct pci_dev *PIIX4_dev)
 {
···
 	return piix4_smba;
 }
 
-static int piix4_transaction(struct i2c_adapter *piix4_adapter, unsigned short piix4_smba)
+int piix4_transaction(struct i2c_adapter *piix4_adapter, unsigned short piix4_smba)
 {
 	int temp;
 	int result = 0;
···
 		inb_p(SMBHSTDAT1));
 	return result;
 }
+EXPORT_SYMBOL_NS_GPL(piix4_transaction, PIIX4_SMBUS);
 
 /* Return negative errno on error. */
 static s32 piix4_access(struct i2c_adapter * adap, u16 addr,
···
 	release_region(KERNCZ_IMC_IDX, 2);
 }
 
-static int piix4_sb800_port_sel(u8 port, struct sb800_mmio_cfg *mmio_cfg)
+int piix4_sb800_port_sel(u8 port, struct sb800_mmio_cfg *mmio_cfg)
 {
 	u8 smba_en_lo, val;
 
···
 
 	return (smba_en_lo & piix4_port_mask_sb800);
 }
+EXPORT_SYMBOL_NS_GPL(piix4_sb800_port_sel, PIIX4_SMBUS);
 
 /*
  * Handles access to multiple SMBus ports on the SB800.

drivers/i2c/busses/i2c-piix4.h

···
 	bool use_mmio;
 };
 
+int piix4_sb800_port_sel(u8 port, struct sb800_mmio_cfg *mmio_cfg);
+int piix4_transaction(struct i2c_adapter *piix4_adapter, unsigned short piix4_smba);
+int piix4_sb800_region_request(struct device *dev, struct sb800_mmio_cfg *mmio_cfg);
+void piix4_sb800_region_release(struct device *dev, struct sb800_mmio_cfg *mmio_cfg);
+
 #endif /* I2C_PIIX4_H */