phy: Allow multiple mark bytes before SOM

The specification requires the transmitting devices to allow an
equivalent of 2 character time as idle time between packets. It also
mentions that it must drive the line to all-high (done by sending 0xFF
over the wire) for a minimum of 1 character width.

The combination of these two should yield a pause of 2 char, and a mark
of 1 char (UART start bit is 0). But some devices my chose to send more
than one mark byte and we will be a bit more lenient to allow this.

Signed-off-by: Siddharth Chandrasekaran <[email protected]>

src/osdp_phy.c

@@ -346,15 +346,15 @@ static int phy_check_header(struct osdp_pd *pd)
 				buf[0] = OSDP_PKT_MARK;
 				buf[1] = OSDP_PKT_SOM;
 				pd->packet_buf_len = 2;
-				pd->packet_scan_skip--;
 				SET_FLAG(pd, PD_FLAG_PKT_HAS_MARK);
 			} else {
 				buf[0] = OSDP_PKT_SOM;
 				pd->packet_buf_len = 1;
 				CLEAR_FLAG(pd, PD_FLAG_PKT_HAS_MARK);
 			}
 			break;
-		} else {
+		}
+		if (cur_byte != OSDP_PKT_MARK) {
 			pd->packet_scan_skip++;
 		}
 		prev_byte = cur_byte;