[PATCH v2 3/3] ACPI: a missing FACS table can be ignored under some circumstances

[Fu Wei]

(1)Both of the FADT fields FIRMWARE_CTRL and X_FIRMWARE_CTRL
 are allowed to be null, if and only if ACPI is operating in hardware- reduced
 mode.
(2)If the ACPI tables are from before ACPI 5.0, or if ACPI is not
 operating in hardware-reduced mode, at least one of the FIRMWARE_CTRL or
 X_FIRMWARE_CTRL fields _must_ be non-null.

This patch corrects the logic to ensure that a missing FACS is only
allowed under the proper circumstances.

Signed-off-by: Fu Wei <fu.wei at linaro.org>
Acked-by: Hanjun Guo <hanjun.guo at linaro.org>
Reviewed-by: Al Stone <al.stone at linaro.org>
---
 src/acpi/acpitables/acpitables.c |  5 +++--
 src/lib/src/fwts_acpi_tables.c   | 24 +++++++++++++++++-------
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/src/acpi/acpitables/acpitables.c b/src/acpi/acpitables/acpitables.c
index 255261c..3d261cb 100644
--- a/src/acpi/acpitables/acpitables.c
+++ b/src/acpi/acpitables/acpitables.c
@@ -75,10 +75,11 @@ static void acpi_table_check_fadt(fwts_framework *fw, fwts_acpi_table_info *tabl
 
 	if (fadt->firmware_control == 0) {
 		if (table->length >= 140) {
-			if (fadt->x_firmware_ctrl == 0) {
+			if ((fadt->x_firmware_ctrl == 0) && !(fwts_acpi_is_reduced_hardware(fadt))) {
 				fwts_failed(fw, LOG_LEVEL_CRITICAL, "FADTFACSZero", "FADT 32 bit FIRMWARE_CONTROL and 64 bit X_FIRMWARE_CONTROL (FACS address) are null.");
 				fwts_advice(fw, "The 32 bit FIRMWARE_CTRL or 64 bit X_FIRMWARE_CTRL should point to a valid "
-						"Firmware ACPI Control Structure (FACS). This is a firmware bug and needs to be fixed.");
+						"Firmware ACPI Control Structure (FACS) when ACPI hardware reduced mode is not set. "
+						"This is a firmware bug and needs to be fixed.");
 			}
 		} else {
 			fwts_failed(fw, LOG_LEVEL_MEDIUM, "FADT32BitFACSNull", "FADT 32 bit FIRMWARE_CONTROL is null.");
diff --git a/src/lib/src/fwts_acpi_tables.c b/src/lib/src/fwts_acpi_tables.c
index ee592d6..68211e5 100644
--- a/src/lib/src/fwts_acpi_tables.c
+++ b/src/lib/src/fwts_acpi_tables.c
@@ -373,6 +373,7 @@ static int fwts_acpi_handle_fadt(
 	const fwts_acpi_table_provenance provenance)
 {
 	static uint64_t	facs_last_phys_addr;	/* default to zero */
+	int result = FWTS_ERROR;
 
 	/*
 	 *  The FADT handling may occur twice if it appears
@@ -384,13 +385,22 @@ static int fwts_acpi_handle_fadt(
 
 	facs_last_phys_addr = phys_addr;
 
-	/* Determine FACS addr and load it */
-	if (fwts_acpi_handle_fadt_tables(fw, fadt,
-	    "FACS", "FIRMWARE_CTRL", "X_FIRMWARE_CTRL",
-	     &fadt->firmware_control, &fadt->x_firmware_ctrl,
-	     provenance) != FWTS_OK) {
-		fwts_log_error(fw, "Failed to load FACS.");
-		return FWTS_ERROR;
+	/* Determine FACS addr and load it.
+	 * Will ignore the missing FACS in the hardware-reduced mode.
+	 */
+	result = fwts_acpi_handle_fadt_tables(fw, fadt,
+			"FACS", "FIRMWARE_CTRL", "X_FIRMWARE_CTRL",
+			&fadt->firmware_control, &fadt->x_firmware_ctrl,
+			provenance);
+	if (result != FWTS_OK) {
+		if ((result == FWTS_NULL_POINTER) &&
+				fwts_acpi_is_reduced_hardware(fadt)) {
+			fwts_log_info(fw, "Ignore the missing FACS. "
+					"It is optional in hardware-reduced mode");
+		} else {
+			fwts_log_error(fw, "Failed to load FACS.");
+			return FWTS_ERROR;
+		}
 	}
 	/* Determine DSDT addr and load it */
 	if (fwts_acpi_handle_fadt_tables(fw, fadt,
-- 
1.8.3.1