acpi_spmc(4): Factor out testing for present DSMs/functions

Since we are now keeping in the softc the information about which DSM
functions are available (in supported_functions[]), the 'dsms' field
there is somewhat redundant.

Make it completely redundant by keeping the bit representing the
enumeration function itself in each element of supported_functions[],
and then remove the field.

As a result, convert has_dsm() to rely on supports_function().

Adapt acpi_spmc_dsm_check_functions() so that it does not take into
account the enumeration function bit.

While here, use the self-explanatory stance
IDX_TO_BIT(DSM_ENUM_FUNCTIONS) instead of a hardcoded 1.

Reviewed by:    obiwac
Sponsored by:   The FreeBSD Foundation
Differential Revision:  https://reviews.freebsd.org/D56878

sys/dev/acpica/acpi_spmc.c

@@ -223,7 +223,6 @@ struct acpi_spmc_constraint {
 struct acpi_spmc_softc {
 	device_t		dev;
 	ACPI_HANDLE		handle;
-	int			dsms;
 	uint64_t		supported_functions[nitems(dsms)];
 
 	struct eventhandler_entry	*eh_suspend;
@@ -257,7 +256,7 @@ supports_function(const struct acpi_spmc_softc *const sc, const int dsm_index,
 static bool
 has_dsm(const struct acpi_spmc_softc *const sc, const int dsm_index)
 {
-	return ((sc->dsms & IDX_TO_BIT(dsm_index)) != 0);
+	return (supports_function(sc, dsm_index, DSM_ENUM_FUNCTIONS));
 }
 
 typedef const char *pbf_get_name_t(const int, const void *const);
@@ -371,6 +370,7 @@ acpi_spmc_attach(device_t dev)
 {
 	struct acpi_spmc_softc *const sc = device_get_softc(dev);
 	const ACPI_HANDLE handle = acpi_get_handle(dev);
+	int supported_dsms;
 	char buf[32];
 	int error;
 
@@ -382,6 +382,7 @@ acpi_spmc_attach(device_t dev)
 	sc->dev = dev;
 	sc->handle = handle;
 
+	supported_dsms = 0;
 	for (int i = 0; i < nitems(dsms); ++i) {
 		KASSERT(dsms[i] != NULL, ("%s: Sparse dsms[]!", __func__));
 		KASSERT(dsms[i]->index == i,
@@ -389,14 +390,17 @@ acpi_spmc_attach(device_t dev)
 		    dsms[i]->name));
 
 		acpi_spmc_probe_dsm(sc, dsms[i]);
+		if (has_dsm(sc, i))
+			supported_dsms |= IDX_TO_BIT(i);
 	}
 
-	if (sc->dsms == 0) {
+	if (supported_dsms == 0) {
 		device_printf(dev, "No DSM supported!");
 		return (ENXIO);
 	}
 
-	print_bit_field(buf, sizeof(buf), sc->dsms, "DSM", pbf_dsm_name, NULL);
+	print_bit_field(buf, sizeof(buf), supported_dsms, "DSM",
+	    pbf_dsm_name, NULL);
 	device_printf(dev, "DSMs supported: %s\n", buf);
 
 	/* Print supported functions of usable DSMs. */
@@ -436,7 +440,12 @@ static void
 acpi_spmc_dsm_print_functions(const struct acpi_spmc_softc *const sc,
     const struct dsm_desc *const dsm)
 {
-	const uint64_t supported_functions =
+	/*
+	 * Remove the enumeration function bit, which we do not care about when
+	 * printing which functions are supported and which we do not want to
+	 * report as unknown.
+	 */
+	const uint64_t supported_functions = ~IDX_TO_BIT(DSM_ENUM_FUNCTIONS) &
 	    sc->supported_functions[dsm->index];
 	const uint64_t missing = dsm->expected_functions & ~supported_functions;
 	const uint64_t unknown = supported_functions &
@@ -475,10 +484,9 @@ acpi_spmc_probe_dsm(struct acpi_spmc_softc *const sc,
 	/*
 	 * DSM is supported if bit 0 is set.
 	 */
-	if ((supported_functions & 1) == 0)
+	if ((supported_functions & IDX_TO_BIT(DSM_ENUM_FUNCTIONS)) == 0)
 		return;
-	sc->supported_functions[dsm->index] = supported_functions & ~1;
-	sc->dsms |= IDX_TO_BIT(dsm->index);
+	sc->supported_functions[dsm->index] = supported_functions;
 }
 
 static void