device/i2c_bus: allow i2c_bus and i2c_simple to coexist

If one wants to implement both i2c_bus.h and i2c_simple.h APIs
the compilation unit needs to be guarded or coordinated carefully
with different compilation units. Instead, name the i2c_bus
functions with _dev such that it indicates that they operate on
struct device. One other change to allow i2c_bus.h to be built in
non-ramstage environments is to ensure DEVTREE_CONST is used for
the dev field in struct bus.

BUG=b:72121803

Change-Id: I267e27e62c95013e8ff8b0728dbe9e7b523de453
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/23370
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/device/i2c_bus.c

@@ -44,7 +44,7 @@ struct bus *i2c_link(struct device *const dev)
 	return link;
 }
 
-int i2c_readb(struct device *const dev)
+int i2c_dev_readb(struct device *const dev)
 {
 	struct device *const busdev = i2c_busdev(dev);
 	if (!busdev)
@@ -74,7 +74,7 @@ int i2c_readb(struct device *const dev)
 	}
 }
 
-int i2c_writeb(struct device *const dev, uint8_t val)
+int i2c_dev_writeb(struct device *const dev, uint8_t val)
 {
 	struct device *const busdev = i2c_busdev(dev);
 	if (!busdev)
@@ -97,7 +97,7 @@ int i2c_writeb(struct device *const dev, uint8_t val)
 	}
 }
 
-int i2c_readb_at(struct device *const dev, uint8_t off)
+int i2c_dev_readb_at(struct device *const dev, uint8_t off)
 {
 	struct device *const busdev = i2c_busdev(dev);
 	if (!busdev)
@@ -135,8 +135,8 @@ int i2c_readb_at(struct device *const dev, uint8_t off)
 	}
 }
 
-int i2c_writeb_at(struct device *const dev,
-		  const uint8_t off, const uint8_t val)
+int i2c_dev_writeb_at(struct device *const dev,
+			const uint8_t off, const uint8_t val)
 {
 	struct device *const busdev = i2c_busdev(dev);
 	if (!busdev)

src/drivers/i2c/rx6110sa/rx6110sa.c

@@ -25,13 +25,13 @@
 /* Function to write a register in the RTC with the given value. */
 static void rx6110sa_write(struct device *dev, uint8_t reg, uint8_t val)
 {
-	i2c_writeb_at(dev, reg, val);
+	i2c_dev_writeb_at(dev, reg, val);
 }
 
 /* Function to read a register in the RTC. */
 static uint8_t rx6110sa_read(struct device *dev, uint8_t reg)
 {
-	return (uint8_t)i2c_readb_at(dev, reg);
+	return (uint8_t)i2c_dev_readb_at(dev, reg);
 }
 
 /* Set RTC date from coreboot build date. */

src/include/device/i2c_bus.h

@@ -39,7 +39,7 @@ struct bus *i2c_link(struct device *);
  *
  * Returns NULL if i2c_link(dev) returns NULL.
  */
-static inline struct device *i2c_busdev(struct device *dev)
+static inline DEVTREE_CONST struct device *i2c_busdev(struct device *dev)
 {
 	struct bus *const link = i2c_link(dev);
 	return link ? link->dev : NULL;
@@ -63,7 +63,7 @@ static inline struct device *i2c_busdev(struct device *dev)
  *
  * Returns the read byte on success, negative `enum cb_err` value on error.
  */
-int i2c_readb(struct device *);
+int i2c_dev_readb(struct device *);
 
 /*
  * Writes the byte `val`.
@@ -71,7 +71,7 @@ int i2c_readb(struct device *);
  *
  * Returns 0 on success, negative `enum cb_err` value on error.
  */
-int i2c_writeb(struct device *, uint8_t val);
+int i2c_dev_writeb(struct device *, uint8_t val);
 
 /*
  * Sends the register offset `off` and reads one byte.
@@ -79,7 +79,7 @@ int i2c_writeb(struct device *, uint8_t val);
  *
  * Returns the read byte on success, negative `enum cb_err` value on error.
  */
-int i2c_readb_at(struct device *, uint8_t off);
+int i2c_dev_readb_at(struct device *, uint8_t off);
 
 /*
  * Sends the register offset `off` followed by the byte `val`.
@@ -87,6 +87,6 @@ int i2c_readb_at(struct device *, uint8_t off);
  *
  * Returns 0 on success, negative `enum cb_err` value on error.
  */
-int i2c_writeb_at(struct device *, uint8_t off, uint8_t val);
+int i2c_dev_writeb_at(struct device *, uint8_t off, uint8_t val);
 
 #endif	/* _DEVICE_I2C_BUS_H_ */

src/include/device/smbus.h

@@ -32,22 +32,22 @@ int smbus_set_link(device_t dev);
 
 static inline int smbus_recv_byte(struct device *const dev)
 {
-	return i2c_readb(dev);
+	return i2c_dev_readb(dev);
 }
 
 static inline int smbus_send_byte(struct device *const dev, u8 byte)
 {
-	return i2c_writeb(dev, byte);
+	return i2c_dev_writeb(dev, byte);
 }
 
 static inline int smbus_read_byte(struct device *const dev, u8 addr)
 {
-	return i2c_readb_at(dev, addr);
+	return i2c_dev_readb_at(dev, addr);
 }
 
 static inline int smbus_write_byte(struct device *const dev, u8 addr, u8 val)
 {
-	return i2c_writeb_at(dev, addr, val);
+	return i2c_dev_writeb_at(dev, addr, val);
 }
 
 int smbus_block_read(device_t dev, u8 cmd, u8 bytes, u8 *buffer);