longer description of changes

Author: mikeysklar

src/adafruit_blinka/microcontroller/generic_linux/i2c.py

@@ -41,7 +41,13 @@ def __init__(self, bus_num, mode=MASTER, baudrate=None):
     # pylint: enable=unused-argument
 
     def scan(self):
-        """Probe each address; return those that ACK."""
+        """Scan I2C bus for devices.
+
+        On Linux, some devices will NACK SMBus 'read_byte' probes but respond fine
+        to real I2C transactions. Prefer SMBus 'quick' probe when supported, and
+        fall back to 'read_byte'. Skip reserved address ranges by scanning only
+        0x08..0x77.
+        """
         found = []
         for addr in range(0x08, 0x78):
             try: