Index: uchcom.c
===================================================================
RCS file: /cvs/src/sys/dev/usb/uchcom.c,v
retrieving revision 1.19
diff -u -p -u -p -d -r1.19 uchcom.c
--- uchcom.c	15 Nov 2013 10:17:39 -0000	1.19
+++ uchcom.c	15 May 2014 20:04:13 -0000
@@ -91,18 +91,17 @@ int	uchcomdebug = 0;
 #define UCHCOM_BRK1_MASK	0x01
 #define UCHCOM_BRK2_MASK	0x40
 
-#define UCHCOM_LCR1_MASK	0xAF
-#define UCHCOM_LCR2_MASK	0x07
-#define UCHCOM_LCR1_PARENB	0x80
-#define UCHCOM_LCR2_PAREVEN	0x07
-#define UCHCOM_LCR2_PARODD	0x06
-#define UCHCOM_LCR2_PARMARK	0x05
-#define UCHCOM_LCR2_PARSPACE	0x04
-
 #define UCHCOM_INTR_STAT1	0x02
 #define UCHCOM_INTR_STAT2	0x03
 #define UCHCOM_INTR_LEAST	4
 
+/*
+ * XXX - these magic numbers come from Linux (drivers/usb/serial/ch341.c).
+ * The manufacturer was unresponsive when asked for documentation.
+ */
+#define UCHCOM_RESET_VALUE	0x501F	/* line mode? */
+#define UCHCOM_RESET_INDEX	0xD90A	/* baud rate? */
+
 #define UCHCOMIBUFSIZE 256
 #define UCHCOMOBUFSIZE 256
 
@@ -707,27 +706,10 @@ uchcom_set_dte_rate(struct uchcom_softc 
 int
 uchcom_set_line_control(struct uchcom_softc *sc, tcflag_t cflag)
 {
-	usbd_status err;
-	uint8_t lcr1 = 0, lcr2 = 0;
-
-	err = uchcom_read_reg(sc, UCHCOM_REG_LCR1, &lcr1, UCHCOM_REG_LCR2,
-	    &lcr2);
-	if (err) {
-		printf("%s: cannot get LCR: %s\n",
-		       sc->sc_dev.dv_xname, usbd_errstr(err));
-		return EIO;
-	}
-
-	lcr1 &= ~UCHCOM_LCR1_MASK;
-	lcr2 &= ~UCHCOM_LCR2_MASK;
-
 	/*
 	 * XXX: it is difficult to handle the line control appropriately:
-	 *   - CS8, !CSTOPB and any parity mode seems ok, but
-	 *   - the chip doesn't have the function to calculate parity
-	 *     in !CS8 mode.
-	 *   - it is unclear that the chip supports CS5,6 mode.
-	 *   - it is unclear how to handle stop bits.
+	 *   work as chip default - CS8, no parity, !CSTOPB
+	 *   other modes are not supported.
 	 */
 
 	switch (ISSET(cflag, CSIZE)) {
@@ -739,21 +721,8 @@ uchcom_set_line_control(struct uchcom_so
 		break;
 	}
 
-	if (ISSET(cflag, PARENB)) {
-		lcr1 |= UCHCOM_LCR1_PARENB;
-		if (ISSET(cflag, PARODD))
-			lcr2 |= UCHCOM_LCR2_PARODD;
-		else
-			lcr2 |= UCHCOM_LCR2_PAREVEN;
-	}
-
-	err = uchcom_write_reg(sc, UCHCOM_REG_LCR1, lcr1, UCHCOM_REG_LCR2,
-	    lcr2);
-	if (err) {
-		printf("%s: cannot set LCR: %s\n",
-		       sc->sc_dev.dv_xname, usbd_errstr(err));
-		return EIO;
-	}
+	if (ISSET(cflag, PARENB) || ISSET(cflag, CSTOPB))
+		return EINVAL;
 
 	return 0;
 }
@@ -778,38 +747,12 @@ int
 uchcom_reset_chip(struct uchcom_softc *sc)
 {
 	usbd_status err;
-	uint8_t lcr1, lcr2, pre, div, mod;
-	uint16_t val=0, idx=0;
 
-	err = uchcom_read_reg(sc, UCHCOM_REG_LCR1, &lcr1, UCHCOM_REG_LCR2, &lcr2);
-	if (err)
-		goto failed;
-
-	err = uchcom_read_reg(sc, UCHCOM_REG_BPS_PRE, &pre, UCHCOM_REG_BPS_DIV,
-	    &div);
-	if (err)
-		goto failed;
-
-	err = uchcom_read_reg(sc, UCHCOM_REG_BPS_MOD, &mod, UCHCOM_REG_BPS_PAD,
-	    NULL);
-	if (err)
-		goto failed;
-
-	val |= (uint16_t)(lcr1&0xF0) << 8;
-	val |= 0x01;
-	val |= (uint16_t)(lcr2&0x0F) << 8;
-	val |= 0x02;
-	idx |= pre & 0x07;
-	val |= 0x04;
-	idx |= (uint16_t)div << 8;
-	val |= 0x08;
-	idx |= mod & 0xF8;
-	val |= 0x10;
-
-	DPRINTF(("%s: reset v=0x%04X, i=0x%04X\n",
-		 sc->sc_dev.dv_xname, val, idx));
+	DPRINTF(("%s: reset\n", sc->sc_dev.dv_xname));
 
-	err = uchcom_generic_control_out(sc, UCHCOM_REQ_RESET, val, idx);
+	err = uchcom_generic_control_out(sc, UCHCOM_REQ_RESET,
+					 UCHCOM_RESET_VALUE,
+					 UCHCOM_RESET_INDEX);
 	if (err)
 		goto failed;