Change ST7789 SPI driver to require SPI bus instead of initializing it

Improves behavior when using the same SPI bus with multiple devices, like an SD card
Also modify DC pin behavior to restore previous mode/alt parameters after communicating with display, in case the pin is used by another device (eg. SPI by SD card)

Author: sfe-SparkFro

drivers/display/st7789_spi.py

@@ -118,15 +118,11 @@ class ST7789_SPI():
     OpenCV SPI driver for ST7789 displays
 
     Args:
-        width (int): display width   **Required**
+        width (int): display width **Required**
         height (int): display height **Required**
-        spi_id (int): SPI bus ID
-        spi_baudrate (int): SPI baudrate, default 24MHz
-        pin_sck (pin): SCK pin number
-        pin_mosi (pin): MOSI pin number
-        pin_miso (pin): MISO pin number
-        pin_cs (pin): Chip Select pin number
-        pin_dc (pin): Data/Command pin number
+        spi (SPI): SPI bus **Required**
+        pin_dc (Pin): Data/Command pin number **Required**
+        pin_cs (Pin): Chip Select pin number
         rotation (int): Orientation of display
           - 0-Portrait, default
           - 1-Landscape
@@ -142,24 +138,17 @@ def __init__(
         self,
         width,
         height,
-        spi_id,
-        spi_baudrate=24000000,
-        pin_sck=None,
-        pin_mosi=None,
-        pin_miso=None,
+        spi,
+        pin_dc,
         pin_cs=None,
-        pin_dc=None,
         rotation=0,
         color_order=BGR,
         reverse_bytes_in_word=True,
     ):
         # Store SPI arguments
-        self.spi = SPI(spi_id, baudrate=spi_baudrate,
-                       sck=Pin(pin_sck, Pin.OUT) if pin_sck else None,
-                       mosi=Pin(pin_mosi, Pin.OUT) if pin_mosi else None,
-                       miso=Pin(pin_miso, Pin.IN) if pin_miso else None)
+        self.spi = spi
+        self.dc = Pin(pin_dc) # Don't change mode/alt
         self.cs = Pin(pin_cs, Pin.OUT, value=1) if pin_cs else None
-        self.dc = Pin(pin_dc, Pin.OUT, value=1) if pin_dc else None
         # Initial dimensions and offsets; will be overridden when rotation applied
         self.width = width
         self.height = height
@@ -359,8 +348,54 @@ def clear(self):
         # Write the buffer to the display
         self._write(None, self.buffer)
 
+    def saveDcPin(self):
+        """
+        Saves the current `mode` and `alt` of the DC pin so it can be restored
+        later. Mostly used to restore the SPI mode (MISO) of the DC pin after
+        communication with the display in case another device is using the same
+        SPI bus.
+
+        Returns:
+            tuple: (mode, alt)
+        """
+        # There's no way to get the mode and alt of a pin directly, so we
+        # convert the pin to a string and parse it. Example format:
+        # "Pin(GPIO16, mode=ALT, alt=SPI)"
+        dcStr = str(self.dc)
+
+        # Extract the "mode" parameter from the pin string
+        if "mode=" in dcStr:
+            # Split between "mode=" and the next comma or closing parenthesis
+            modeStr = dcStr.split("mode=")[1].split(",")[0].split(")")[0]
+
+            # Look up the mode in Pin class dictionary
+            mode = Pin.__dict__[modeStr]
+        else:
+            # No mode specified, just set to None
+            mode = None
+
+        # Extrct the "alt" parameter from the pin string
+        if "alt=" in dcStr:
+            # Split between "alt=" and the next comma or closing parenthesis
+            altStr = dcStr.split("alt=")[1].split(",")[0].split(")")[0]
+
+            # Look up the alt in Pin class dictionary (with "ALT_" prefix)
+            alt = Pin.__dict__["ALT_" + altStr]
+        else:
+            # No alt specified, just set to None
+            alt = None
+
+        # Return the mode and alt as a tuple
+        return (mode, alt)
+
     def _write(self, command=None, data=None):
         """SPI write to the device: commands and data."""
+        # Save the current mode and alt of the DC pin in case it's used by
+        # another device on the same SPI bus
+        mode, alt = self.saveDcPin()
+        # Temporarily set the DC pin to output mode
+        self.dc.init(mode=Pin.OUT)
+
         if self.cs:
             self.cs.off()
         if command is not None:
@@ -371,3 +406,6 @@ def _write(self, command=None, data=None):
             self.spi.write(data)
         if self.cs:
             self.cs.on()
+
+        # Restore the DC pin to its original mode and alt
+        self.dc.init(mode=mode, alt=alt)