When the user overrides the DSDT, replace any SSDTs with a simple no-op

table.  acpidump(8) concatenates the body of the DSDT and SSDTs so an
edited ASL will contain all the necessary information.  We can't use a
completely empty table since ACPI-CA reports this as a problem.

MFC after:	3 days

1 files changed, 40 insertions, 10 deletions

diff --git a/sys/dev/acpica/Osd/OsdTable.c b/sys/dev/acpica/Osd/OsdTable.c
index 298c965..0ce25d2 100644
--- a/sys/dev/acpica/Osd/OsdTable.c
+++ b/sys/dev/acpica/Osd/OsdTable.c
@@ -30,17 +30,25 @@
  * ACPI Table interfaces
  */
 
-#include "acpi.h"
-
+#include <sys/param.h>
+#include <sys/endian.h>
 #include <sys/kernel.h>
 #include <sys/linker.h>
 
+#include "acpi.h"
+#include <contrib/dev/acpica/actables.h>
+
 #undef _COMPONENT
 #define _COMPONENT      ACPI_TABLES
 
 static char acpi_osname[128];
 TUNABLE_STR("hw.acpi.osname", acpi_osname, sizeof(acpi_osname));
 
+static struct {
+    ACPI_TABLE_HEADER_DEF
+    uint32_t no_op;
+} __packed fake_ssdt;
+
 ACPI_STATUS
 AcpiOsPredefinedOverride (
     const ACPI_PREDEFINED_NAMES *InitVal,
@@ -63,20 +71,42 @@ AcpiOsTableOverride (
     ACPI_TABLE_HEADER       *ExistingTable,
     ACPI_TABLE_HEADER       **NewTable)
 {
-    caddr_t                 acpi_dsdt, p;
+    caddr_t acpi_dsdt, p;
 
     if (ExistingTable == NULL || NewTable == NULL)
-        return(AE_BAD_PARAMETER);
+	return (AE_BAD_PARAMETER);
 
+    /* If we're not overriding the DSDT, just return. */
     *NewTable = NULL;
-    if (strncmp(ExistingTable->Signature, "DSDT", 4) != 0)
-        return(AE_OK);
     if ((acpi_dsdt = preload_search_by_type("acpi_dsdt")) == NULL)
-        return(AE_OK);
+	return (AE_OK);
     if ((p = preload_search_info(acpi_dsdt, MODINFO_ADDR)) == NULL)
-        return(AE_OK);
+	return (AE_OK);
+
+    /*
+     * Override the DSDT with the user's custom version.  Override the
+     * contents of any SSDTs with a simple no-op table since the user's
+     * DSDT is expected to contain their contents as well.
+     */
+    if (strncmp(ExistingTable->Signature, "DSDT", 4) == 0) {
+	printf("ACPI: overriding DSDT/SSDT with custom table\n");
+	*NewTable = *(void **)p;
+    } else if (strncmp(ExistingTable->Signature, "SSDT", 4) == 0) {
+	if (fake_ssdt.Length == 0) {
+	    sprintf(fake_ssdt.Signature, "%.4s", "SSDT");
+	    fake_ssdt.Length = htole32(sizeof(fake_ssdt));
+	    fake_ssdt.Revision = 2;
+	    fake_ssdt.Checksum = 0;
+	    sprintf(fake_ssdt.OemId, "%.6s", "FBSD  ");
+	    sprintf(fake_ssdt.OemTableId, "%.8s", "NullSSDT");
+	    fake_ssdt.OemRevision = htole32(1);
+	    sprintf(fake_ssdt.AslCompilerId, "%.4s", "FBSD");
+	    fake_ssdt.AslCompilerRevision = htole32(1);
+	    fake_ssdt.no_op = htole32(0x005c0310); /* Scope(\) */
+	    fake_ssdt.Checksum -= AcpiTbChecksum(&fake_ssdt, sizeof(fake_ssdt));
+	}
+	*NewTable = (void *)&fake_ssdt;
+    }
 
-    *NewTable = *(void **)p;
-    printf("ACPI: DSDT was overridden.\n");
     return (AE_OK);
 }