drivers: ssd1306: cleanup and make functions static

Cleanup and make functions static.

Signed-off-by: Johann Fischer <[email protected]>

Author: jfischer-no

drivers/display/ssd1306.c

@@ -169,33 +169,28 @@ static inline int ssd1306_set_charge_pump(const struct device *dev)
 			 DT_INST_0_SOLOMON_SSD1306FB_BASE_ADDRESS);
 }
 
-int ssd1306_resume(const struct device *dev)
+static int ssd1306_resume(const struct device *dev)
 {
 	struct ssd1306_data *driver = dev->driver_data;
 	/* set display on */
 	return ssd1306_reg_write(driver, SSD1306_CONTROL_LAST_BYTE_CMD,
 				 SSD1306_DISPLAY_ON);
 }
 
-int ssd1306_suspend(const struct device *dev)
+static int ssd1306_suspend(const struct device *dev)
 {
 	struct ssd1306_data *driver = dev->driver_data;
 	/* set display on */
 	return ssd1306_reg_write(driver, SSD1306_CONTROL_LAST_BYTE_CMD,
 				 SSD1306_DISPLAY_OFF);
 }
 
-int ssd1306_write_page(const struct device *dev, u8_t page, void const *data,
-		       size_t length)
+#if defined(CONFIG_SSD1306_SH1106_COMPATIBLE)
+static int ssd1306_write_page(const struct device *dev, u8_t page,
+			      void const *data, size_t length)
 {
 	struct ssd1306_data *driver = dev->driver_data;
 	u8_t cmd_buf[] = {
-#ifdef OLED_PANEL_CONTROLLER_SSD1306
-		SSD1306_CONTROL_BYTE_CMD,
-		SSD1306_SET_MEM_ADDRESSING_MODE,
-		SSD1306_CONTROL_BYTE_CMD,
-		SSD1306_SET_MEM_ADDRESSING_PAGE,
-#endif
 		SSD1306_CONTROL_BYTE_CMD,
 		SSD1306_SET_LOWER_COL_ADDRESS |
 		(DT_INST_0_SOLOMON_SSD1306FB_SEGMENT_OFFSET &
@@ -226,10 +221,11 @@ int ssd1306_write_page(const struct device *dev, u8_t page, void const *data,
 			       SSD1306_CONTROL_LAST_BYTE_DATA,
 			       data, length);
 }
+#endif
 
-int ssd1306_write(const struct device *dev, const u16_t x, const u16_t y,
-		  const struct display_buffer_descriptor *desc,
-		  const void *buf)
+static int ssd1306_write(const struct device *dev, const u16_t x, const u16_t y,
+			 const struct display_buffer_descriptor *desc,
+			 const void *buf)
 {
 	size_t buf_len;
 
@@ -332,7 +328,7 @@ static int ssd1306_set_brightness(const struct device *dev,
 	return -ENOTSUP;
 }
 
-int ssd1306_set_contrast(const struct device *dev, const u8_t contrast)
+static int ssd1306_set_contrast(const struct device *dev, const u8_t contrast)
 {
 	struct ssd1306_data *driver = dev->driver_data;
 	u8_t cmd_buf[] = {