Only probe the UART type if sc_uarttype is set to COM_UART_UNKNOWN.

This allows glue drivers to set the type based on other information (such as
Oopen Firmware or device tree properties) without going through to risky
code paths.

ok deraadt@, visa@

diff --git a/sys/dev/ic/com.c b/sys/dev/ic/com.c
index 000eea3..b378ffc 100644 (file)
--- a/sys/dev/ic/com.c
+++ b/sys/dev/ic/com.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: com.c,v 1.158 2014/09/14 14:17:24 jsg Exp $   */
+/*     $OpenBSD: com.c,v 1.159 2016/08/16 08:15:04 kettenis Exp $      */
 /*     $NetBSD: com.c,v 1.82.4.1 1996/06/02 09:08:00 mrg Exp $ */
 
 /*
@@ -1583,6 +1583,7 @@ com_attach_subr(struct com_softc *sc)
 {
        bus_space_tag_t iot = sc->sc_iot;
        bus_space_handle_t ioh = sc->sc_ioh;
+       int probe = 0;
        u_int8_t lcr;
 
        sc->sc_ier = 0;
@@ -1616,7 +1617,7 @@ com_attach_subr(struct com_softc *sc)
        /*
         * Skip specific probes if attachment code knows it already.
         */
-       if (sc->sc_uarttype == COM_UART_UNKNOWN)
+       if (sc->sc_uarttype == COM_UART_UNKNOWN) {
                switch (bus_space_read_1(iot, ioh, com_iir) >> 6) {
                case 0:
                        sc->sc_uarttype = COM_UART_16450;
@@ -1631,8 +1632,11 @@ com_attach_subr(struct com_softc *sc)
                        sc->sc_uarttype = COM_UART_UNKNOWN;
                        break;
                }
+               probe = 1;
+       }
 
-       if (sc->sc_uarttype == COM_UART_16550A) { /* Probe for ST16650s */
+       /* Probe for ST16650s */
+       if (probe && sc->sc_uarttype == COM_UART_16550A) {
                bus_space_write_1(iot, ioh, com_lcr, lcr | LCR_DLAB);
                if (bus_space_read_1(iot, ioh, com_efr) == 0) {
                        bus_space_write_1(iot, ioh, com_efr, EFR_CTS);
@@ -1647,7 +1651,8 @@ com_attach_subr(struct com_softc *sc)
        }
 
 #if 0  /* until com works with large FIFOs */
-       if (sc->sc_uarttype == COM_UART_ST16650V2) { /* Probe for XR16850s */
+       /* Probe for XR16850s */
+       if (probe && sc->sc_uarttype == COM_UART_ST16650V2) {
                u_int8_t dlbl, dlbh;
 
                /* Enable latch access and get the current values. */
@@ -1670,7 +1675,8 @@ com_attach_subr(struct com_softc *sc)
        }
 #endif
 
-       if (sc->sc_uarttype == COM_UART_16550A) { /* Probe for TI16750s */
+       /* Probe for TI16750s */
+       if (probe && sc->sc_uarttype == COM_UART_16550A) {
                bus_space_write_1(iot, ioh, com_lcr, lcr | LCR_DLAB);
                bus_space_write_1(iot, ioh, com_fifo,
                    FIFO_ENABLE | FIFO_ENABLE_64BYTE);
@@ -1686,7 +1692,9 @@ com_attach_subr(struct com_softc *sc)
 
        /* Reset the LCR (latch access is probably enabled). */
        bus_space_write_1(iot, ioh, com_lcr, lcr);
-       if (sc->sc_uarttype == COM_UART_16450) { /* Probe for 8250 */
+
+       /* Probe for 8250 */
+       if (probe && sc->sc_uarttype == COM_UART_16450) {
                u_int8_t scr0, scr1, scr2;
 
                scr0 = bus_space_read_1(iot, ioh, com_scratch);