ACPI: GED: add support for _Exx / _Lxx handler methods

Per the ACPI spec, interrupts in the range [0, 255] may be handled
in AML using individual methods whose naming is based on the format
_Exx or _Lxx, where xx is the hex representation of the interrupt
index.

Add support for this missing feature to our ACPI GED driver.

Cc: v4.9+ <stable@vger.kernel.org> # v4.9+
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/evged.c

@@ -79,6 +79,8 @@ static acpi_status acpi_ged_request_interrupt(struct acpi_resource *ares,
 	struct resource r;
 	struct acpi_resource_irq *p = &ares->data.irq;
 	struct acpi_resource_extended_irq *pext = &ares->data.extended_irq;
+	char ev_name[5];
+	u8 trigger;
 
 	if (ares->type == ACPI_RESOURCE_TYPE_END_TAG)
 		return AE_OK;
@@ -87,14 +89,28 @@ static acpi_status acpi_ged_request_interrupt(struct acpi_resource *ares,
 		dev_err(dev, "unable to parse IRQ resource\n");
 		return AE_ERROR;
 	}
-	if (ares->type == ACPI_RESOURCE_TYPE_IRQ)
+	if (ares->type == ACPI_RESOURCE_TYPE_IRQ) {
 		gsi = p->interrupts[0];
-	else
+		trigger = p->triggering;
+	} else {
 		gsi = pext->interrupts[0];
+		trigger = p->triggering;
+	}
 
 	irq = r.start;
 
-	if (ACPI_FAILURE(acpi_get_handle(handle, "_EVT", &evt_handle))) {
+	switch (gsi) {
+	case 0 ... 255:
+		sprintf(ev_name, "_%c%02hhX",
+			trigger == ACPI_EDGE_SENSITIVE ? 'E' : 'L', gsi);
+
+		if (ACPI_SUCCESS(acpi_get_handle(handle, ev_name, &evt_handle)))
+			break;
+		/* fall through */
+	default:
+		if (ACPI_SUCCESS(acpi_get_handle(handle, "_EVT", &evt_handle)))
+			break;
+
 		dev_err(dev, "cannot locate _EVT method\n");
 		return AE_ERROR;
 	}