[v1,18/35] acpi: Support writing a UUID

diff --git a/include/acpi/acpigen.h b/include/acpi/acpigen.h
index 0fecb7d57a..f35467f029 100644
--- a/include/acpi/acpigen.h
+++ b/include/acpi/acpigen.h
@@ -24,6 +24,7 @@  enum {
 	DWORD_PREFIX		= 0x0c,
 	STRING_PREFIX		= 0x0d,
 	QWORD_PREFIX		= 0x0e,
+	BUFFER_OP		= 0x11,
 	PACKAGE_OP		= 0x12,
 	DUAL_NAME_PREFIX	= 0x2e,
 	MULTI_NAME_PREFIX	= 0x2f,
@@ -182,4 +183,16 @@  void acpigen_emit_namestring(struct acpi_ctx *ctx, const char *namepath);
  * @namepath: Name / path to emit
  */
 void acpigen_write_name(struct acpi_ctx *ctx, const char *namepath);
+
+/**
+ * acpigen_write_uuid() - Write a UUID
+ *
+ * This writes out a UUID in the format used by ACPI, with a BUFFER_OP prefix.
+ *
+ * @ctx: ACPI context pointer
+ * @uuid: UUID to write in the form aabbccdd-eeff-gghh-iijj-kkllmmnnoopp
+ * @return 0 if OK, -EINVAL if the format is incorrect
+ */
+int acpigen_write_uuid(struct acpi_ctx *ctx, const char *uuid);
+
 #endif
diff --git a/lib/acpi/acpigen.c b/lib/acpi/acpigen.c
index 07bd569f26..a61496a095 100644
--- a/lib/acpi/acpigen.c
+++ b/lib/acpi/acpigen.c
@@ -247,3 +247,41 @@  void acpigen_write_name(struct acpi_ctx *ctx, const char *namepath)
 	acpigen_emit_byte(ctx, NAME_OP);
 	acpigen_emit_namestring(ctx, namepath);
 }
+
+/*
+ * ToUUID(uuid)
+ *
+ * ACPI 6.3 Section 19.6.142 table 19-438 defines a special output order for the
+ * bytes that make up a UUID Buffer object:
+ *
+ * UUID byte order for input to this function:
+ *   aabbccdd-eeff-gghh-iijj-kkllmmnnoopp
+ *
+ * UUID byte order output by this function:
+ *   ddccbbaa-ffee-hhgg-iijj-kkllmmnnoopp
+ */
+#define UUID_LEN 16
+int acpigen_write_uuid(struct acpi_ctx *ctx, const char *uuid)
+{
+	u8 buf[UUID_LEN];
+	int ret;
+
+	/* Parse UUID string into bytes */
+	ret = uuid_str_to_bin(uuid, buf, UUID_STR_FORMAT_GUID);
+	if (ret)
+		return log_msg_ret("bad hex", -EINVAL);
+
+	/* BufferOp */
+	acpigen_emit_byte(ctx, BUFFER_OP);
+	acpigen_write_len_f(ctx);
+
+	/* Buffer length in bytes */
+	acpigen_write_word(ctx, UUID_LEN);
+
+	/* Output UUID in expected order */
+	acpigen_emit_stream(ctx, (char *)buf, UUID_LEN);
+
+	acpigen_pop_len(ctx);
+
+	return 0;
+}
diff --git a/test/dm/acpigen.c b/test/dm/acpigen.c
index 0f56262a28..db8cad47d8 100644
--- a/test/dm/acpigen.c
+++ b/test/dm/acpigen.c
@@ -588,3 +588,36 @@  static int dm_test_acpi_name(struct unit_test_state *uts)
 	return 0;
 }
 DM_TEST(dm_test_acpi_name, 0);
+
+/* Test writing a UUID */
+static int dm_test_acpi_uuid(struct unit_test_state *uts)
+{
+	struct acpi_ctx *ctx;
+	u8 *ptr;
+
+	ut_assertok(alloc_context(&ctx));
+
+	ptr = acpigen_get_current(ctx);
+
+	ut_assertok(acpigen_write_uuid(ctx,
+				       "dbb8e3e6-5886-4ba6-8795-1319f52a966b"));
+	ut_asserteq(23, acpigen_get_current(ctx) - ptr);
+	ut_asserteq(BUFFER_OP, ptr[0]);
+	ut_asserteq(22, get_length(ptr + 1));
+	ut_asserteq(0xdbb8e3e6, get_unaligned((u32 *)(ptr + 7)));
+	ut_asserteq(0x5886, get_unaligned((u16 *)(ptr + 11)));
+	ut_asserteq(0x4ba6, get_unaligned((u16 *)(ptr + 13)));
+	ut_asserteq(0x9587, get_unaligned((u16 *)(ptr + 15)));
+	ut_asserteq(0x2af51913, get_unaligned((u32 *)(ptr + 17)));
+	ut_asserteq(0x6b96, get_unaligned((u16 *)(ptr + 21)));
+
+	/* Try a bad UUID */
+	ut_asserteq(-EINVAL,
+		    acpigen_write_uuid(ctx,
+				       "dbb8e3e6-5886-4ba6x8795-1319f52a966b"));
+
+	free_context(&ctx);
+
+	return 0;
+}
+DM_TEST(dm_test_acpi_uuid, 0);