Add an evdev touchscreen driver

driver/linux/evdev.py

@@ -5,6 +5,19 @@
 import select
 import lvgl as lv
 
+EV_REL = 0x02
+EV_ABS = 0x03
+EV_KEY = 0x01
+REL_X = 0x00
+REL_Y = 0x01
+ABS_X = 0x00
+ABS_Y = 0x01
+ABS_MT_POSITION_X = 0x35
+ABS_MT_POSITION_Y = 0x36
+ABS_MT_TRACKING_ID = 0x39
+BTN_MOUSE = 0x110
+BTN_TOUCH = 0x14a
+
 # Default crosshair cursor
 class crosshair_cursor:
     def __init__(self, scr=None):
@@ -80,3 +93,100 @@ def delete(self):
         if self.cursor and hasattr(self.cursor, 'delete'):
             self.cursor.delete()
         self.indev.enable(False)
+
+# evdev driver for touchscreen
+class touch_indev:
+    def __init__(self, scr=None, device='/dev/input/event1', evdev_swap_axes=False):
+
+        # Open evdev and initialize members
+        self.evdev = open(device, 'rb')
+        self.poll = select.poll()
+        self.poll.register(self.evdev.fileno())
+        self.scr = scr if scr else lv.scr_act()
+        self.hor_res = self.scr.get_width()
+        self.ver_res = self.scr.get_height()
+        self.evdev_button = lv.INDEV_STATE.RELEASED
+        self.evdev_swap_axes = evdev_swap_axes
+        self.evdev_calibrate = False
+        self.last_evdev_root_x = 0
+        self.last_evdev_root_y = 0 
+
+    def read(self, indev_drv, data) -> int:
+
+        # Check if there is input to be read from evdev
+        if not self.poll.poll()[0][1] & select.POLLIN:
+            return 0
+
+        FORMAT = 'llHHI'
+        EVENT_SIZE = ustruct.calcsize(FORMAT)
+
+        evdev_root_x = self.last_evdev_root_x
+        evdev_root_y = self.last_evdev_root_y
+
+        raw_data = self.evdev.read(EVENT_SIZE)
+
+        while(self.poll.poll()[0][1] & select.POLLIN):
+
+            # Read and parse evdev data
+            raw_data = self.evdev.read(EVENT_SIZE)
+            (_, _, event_type, code, value) = ustruct.unpack(FORMAT, raw_data)
+
+            if event_type == EV_ABS:
+                if (code == ABS_X) or (code == ABS_MT_POSITION_X):
+                    if self.evdev_swap_axes:
+                        evdev_root_y = value
+                    else:
+                        evdev_root_x = value
+                elif (code == ABS_Y) or (code == ABS_MT_POSITION_Y):
+                    if self.evdev_swap_axes:
+                        evdev_root_x = value
+                    else:
+                        evdev_root_y = value
+                elif code == ABS_MT_TRACKING_ID:
+                    if value == -1:
+                        self.evdev_button = lv.INDEV_STATE.RELEASED
+                    else:
+                        self.evdev_button = lv.INDEV_STATE.PRESSED
+            elif (event_type == EV_KEY) and (code == BTN_TOUCH):
+                if value == 0:
+                    self.evdev_button = lv.INDEV_STATE.RELEASED
+                elif value == 1:
+                    self.evdev_button = lv.INDEV_STATE.PRESSED
+
+        self.last_evdev_root_x = evdev_root_x
+        self.last_evdev_root_y = evdev_root_y
+
+        # Scaling
+        if self.evdev_calibrate:
+            evdev_root_x = self._map_horizontal(evdev_root_x)
+            evdev_root_y = self._map_vertical(evdev_root_y)
+
+        # Handle coordinate overflow cases
+        data.point.x = min(evdev_root_x, self.hor_res - 1)
+        data.point.y = min(evdev_root_y, self.ver_res - 1)
+        data.point.x = max(evdev_root_x, 0)
+        data.point.y = max(evdev_root_y, 0)
+
+        # Update "pressed" status
+        data.state = self.evdev_button
+
+        return 0
+
+    # Scaling: if range of evdev readouts is different than screen resolution
+    # Example for Waveshare 7inch HDMI LCD (C) Rev4.1
+    # touch.calibrate(0, 4096, 0, 4096)
+    def calibrate(self, evdev_min_hor, evdev_max_hor, evdev_min_ver, evdev_max_ver):
+        self.evdev_calibrate = True
+        self.evdev_min_hor = evdev_min_hor
+        self.evdev_max_hor = evdev_max_hor
+        self.evdev_min_ver = evdev_min_ver
+        self.evdev_max_ver = evdev_max_ver
+
+    def _map_vertical(self, val):
+        return int((val - self.evdev_min_ver) * (self.ver_res) / (self.evdev_max_ver - self.evdev_min_ver))
+
+    def _map_horizontal(self, val):
+        return int((val - self.evdev_min_hor) * (self.hor_res) / (self.evdev_max_hor - self.evdev_min_hor))
+
+    def delete(self):
+        self.evdev.close()