acpigen: Add helper functions for strings

Add helper function to emit a string into the SSDT AML bytestream with a
NULL terminator.  Also add a helper function to emit the string OpCode
followed by the string itself.

acpigen_emit_string(string)  /* Raw string output */
acpigen_write_string(string) /* OpCode followed by raw string */

Change-Id: I4a3a8728066e0c41d7ad6429fad983e6ae6962fe
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/14793
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)

src/arch/x86/acpigen.c

@@ -141,6 +141,12 @@ void acpigen_write_name_qword(const char *name, uint64_t val)
 	acpigen_write_qword(val);
 }
 
+void acpigen_write_name_string(const char *name, const char *string)
+{
+	acpigen_write_name(name);
+	acpigen_write_string(string);
+}
+
 void acpigen_emit_stream(const char *data, int size)
 {
 	int i;
@@ -149,6 +155,18 @@ void acpigen_emit_stream(const char *data, int size)
 	}
 }
 
+void acpigen_emit_string(const char *string)
+{
+	acpigen_emit_stream(string, string ? 0 : strlen(string));
+	acpigen_emit_byte('\0'); /* NUL */
+}
+
+void acpigen_write_string(const char *string)
+{
+	acpigen_emit_byte(0x0d);
+	acpigen_emit_string(string);
+}
+
 /*
  * The naming conventions for ACPI namespace names are a bit tricky as
  * each element has to be 4 chars wide (»All names are a fixed 32 bits.«)

src/arch/x86/include/arch/acpigen.h

@@ -32,12 +32,15 @@ void acpigen_emit_byte(unsigned char data);
 void acpigen_emit_word(unsigned int data);
 void acpigen_emit_dword(unsigned int data);
 void acpigen_emit_stream(const char *data, int size);
+void acpigen_emit_string(const char *string);
 void acpigen_emit_namestring(const char *namepath);
 void acpigen_emit_eisaid(const char *eisaid);
 void acpigen_write_word(unsigned int data);
 void acpigen_write_dword(unsigned int data);
 void acpigen_write_qword(uint64_t data);
+void acpigen_write_string(const char *string);
 void acpigen_write_name(const char *name);
+void acpigen_write_name_string(const char *name, const char *string);
 void acpigen_write_name_dword(const char *name, uint32_t val);
 void acpigen_write_name_qword(const char *name, uint64_t val);
 void acpigen_write_name_byte(const char *name, uint8_t val);