acpi_thermal: Warn about insane _TMP temperature only once

A warning is emitted again if the temperature became briefly valid
meanwhile. This avoids spamming the user when the sensor is broken.

Other values (ie. not _TMP) always raise a warning.

sys/dev/acpica/acpi_thermal.c

@@ -111,6 +111,7 @@ struct acpi_tz_softc {
 
     struct acpi_tz_zone 	tz_zone;	/*Thermal zone parameters*/
     int				tz_validchecks;
+    int				tz_insane_tmp_notified;
 
     /* passive cooling */
     struct proc			*tz_cooling_proc;
@@ -161,6 +162,8 @@ static driver_t acpi_tz_driver = {
     sizeof(struct acpi_tz_softc),
 };
 
+static char *acpi_tz_tmp_name = "_TMP";
+
 static devclass_t acpi_tz_devclass;
 DRIVER_MODULE(acpi_tz, acpi, acpi_tz_driver, acpi_tz_devclass, 0, 0);
 MODULE_DEPEND(acpi_tz, acpi, 1, 1, 1);
@@ -456,12 +459,11 @@ acpi_tz_get_temperature(struct acpi_tz_softc *sc)
 {
     int		temp;
     ACPI_STATUS	status;
-    static char	*tmp_name = "_TMP";
 
     ACPI_FUNCTION_NAME ("acpi_tz_get_temperature");
 
     /* Evaluate the thermal zone's _TMP method. */
-    status = acpi_GetInteger(sc->tz_handle, tmp_name, &temp);
+    status = acpi_GetInteger(sc->tz_handle, acpi_tz_tmp_name, &temp);
     if (ACPI_FAILURE(status)) {
 	ACPI_VPRINT(sc->tz_dev, acpi_device_get_parent_softc(sc->tz_dev),
 	    "error fetching current temperature -- %s\n",
@@ -470,7 +472,7 @@ acpi_tz_get_temperature(struct acpi_tz_softc *sc)
     }
 
     /* Check it for validity. */
-    acpi_tz_sanity(sc, &temp, tmp_name);
+    acpi_tz_sanity(sc, &temp, acpi_tz_tmp_name);
     if (temp == -1)
 	return (FALSE);
 
@@ -696,10 +698,29 @@ static void
 acpi_tz_sanity(struct acpi_tz_softc *sc, int *val, char *what)
 {
     if (*val != -1 && (*val < TZ_ZEROC || *val > TZ_ZEROC + 2000)) {
-	device_printf(sc->tz_dev, "%s value is absurd, ignored (%d.%dC)\n",
-		      what, TZ_KELVTOC(*val));
+	/*
+	 * If the value we are checking is _TMP, warn the user only
+	 * once. This avoids spamming messages if, for instance, the
+	 * sensor is broken and always returns an invalid temperature.
+	 *
+	 * This is only done for _TMP; other values always emit a
+	 * warning.
+	 */
+	if (what != acpi_tz_tmp_name || !sc->tz_insane_tmp_notified) {
+	    device_printf(sc->tz_dev, "%s value is absurd, ignored (%d.%dC)\n",
+			  what, TZ_KELVTOC(*val));
+
+	    /* Don't warn the user again if the read value doesn't improve. */
+	    if (what == acpi_tz_tmp_name)
+		sc->tz_insane_tmp_notified = 1;
+	}
 	*val = -1;
+	return;
     }
+
+    /* This value is correct. Warn if it's incorrect again. */
+    if (what == acpi_tz_tmp_name)
+	sc->tz_insane_tmp_notified = 0;
 }
 
 /*