let CH340 chips keep working in 8N1 mode.

they get confused if you try to configure them and don't work at
all otherwise. CH341 seems fine otherwise.

from miod
tested by me and Felix Kronlage-Dam

diff --git a/sys/dev/usb/uchcom.c b/sys/dev/usb/uchcom.c
index 5609ca2..d98c249 100644 (file)
--- a/sys/dev/usb/uchcom.c
+++ b/sys/dev/usb/uchcom.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: uchcom.c,v 1.29 2021/11/02 09:52:40 dlg Exp $ */
+/*     $OpenBSD: uchcom.c,v 1.30 2021/11/19 07:56:53 dlg Exp $ */
 /*     $NetBSD: uchcom.c,v 1.1 2007/09/03 17:57:37 tshiozak Exp $      */
 
 /*
@@ -128,6 +128,7 @@ struct uchcom_softc
        u_char                  *sc_intr_buf;
        int                      sc_isize;
        /* */
+       int                      sc_release;
        uint8_t                  sc_version;
        int                      sc_dtr;
        int                      sc_rts;
@@ -266,10 +267,11 @@ uchcom_attach(struct device *parent, struct device *self, void *aux)
 
         sc->sc_udev = dev;
        sc->sc_dtr = sc->sc_rts = -1;
+       sc->sc_release = uaa->release;
 
        DPRINTF(("\n\nuchcom attach: sc=%p\n", sc));
 
-       switch (uaa->release) {
+       switch (sc->sc_release) {
        case UCHCOM_REV_CH340:
                printf("%s: CH340\n", sc->sc_dev.dv_xname);
                break;
@@ -679,6 +681,26 @@ uchcom_set_line_control(struct uchcom_softc *sc, tcflag_t cflag)
        usbd_status err;
        uint8_t lcr = 0, lcr2 = 0;
 
+       if (sc->sc_release == UCHCOM_REV_CH340) {
+               /*
+                * XXX: it is difficult to handle the line control
+                * appropriately on CH340:
+                *   work as chip default - CS8, no parity, !CSTOPB
+                *   other modes are not supported.
+                */
+               switch (ISSET(cflag, CSIZE)) {
+               case CS5:
+               case CS6:
+               case CS7:
+                       return EINVAL;
+               case CS8:
+                       break;
+               }
+               if (ISSET(cflag, PARENB) || ISSET(cflag, CSTOPB))
+                       return EINVAL;
+               return 0;
+       }
+
        err = uchcom_read_reg(sc, UCHCOM_REG_LCR, &lcr,
            UCHCOM_REG_LCR2, &lcr2);
        if (err) {