ACPI: Teach ACPI table parsing about the CEDT header format

The CEDT adds yet one more unique subtable header type where the length
is a 16-bit value. Extend the subtable helpers to detect this scenario.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Len Brown <lenb@kernel.org>
Tested-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/163553709742.2509508.5177761945441327574.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/acpi/tables.c

@@ -41,6 +41,7 @@ enum acpi_subtable_type {
 	ACPI_SUBTABLE_COMMON,
 	ACPI_SUBTABLE_HMAT,
 	ACPI_SUBTABLE_PRMT,
+	ACPI_SUBTABLE_CEDT,
 };
 
 struct acpi_subtable_entry {
@@ -226,6 +227,8 @@ acpi_get_entry_type(struct acpi_subtable_entry *entry)
 		return entry->hdr->hmat.type;
 	case ACPI_SUBTABLE_PRMT:
 		return 0;
+	case ACPI_SUBTABLE_CEDT:
+		return entry->hdr->cedt.type;
 	}
 	return 0;
 }
@@ -240,6 +243,8 @@ acpi_get_entry_length(struct acpi_subtable_entry *entry)
 		return entry->hdr->hmat.length;
 	case ACPI_SUBTABLE_PRMT:
 		return entry->hdr->prmt.length;
+	case ACPI_SUBTABLE_CEDT:
+		return entry->hdr->cedt.length;
 	}
 	return 0;
 }
@@ -254,6 +259,8 @@ acpi_get_subtable_header_length(struct acpi_subtable_entry *entry)
 		return sizeof(entry->hdr->hmat);
 	case ACPI_SUBTABLE_PRMT:
 		return sizeof(entry->hdr->prmt);
+	case ACPI_SUBTABLE_CEDT:
+		return sizeof(entry->hdr->cedt);
 	}
 	return 0;
 }
@@ -265,6 +272,8 @@ acpi_get_subtable_type(char *id)
 		return ACPI_SUBTABLE_HMAT;
 	if (strncmp(id, ACPI_SIG_PRMT, 4) == 0)
 		return ACPI_SUBTABLE_PRMT;
+	if (strncmp(id, ACPI_SIG_CEDT, 4) == 0)
+		return ACPI_SUBTABLE_CEDT;
 	return ACPI_SUBTABLE_COMMON;
 }
 

include/linux/acpi.h

@@ -133,6 +133,7 @@ union acpi_subtable_headers {
 	struct acpi_subtable_header common;
 	struct acpi_hmat_structure hmat;
 	struct acpi_prmt_module_header prmt;
+	struct acpi_cedt_header cedt;
 };
 
 typedef int (*acpi_tbl_table_handler)(struct acpi_table_header *table);