[v8,14/35] acpigen: Support writing a package

diff --git a/include/acpi/acpigen.h b/include/acpi/acpigen.h
index 31366f5e34..52e0b75128 100644
--- a/include/acpi/acpigen.h
+++ b/include/acpi/acpigen.h
@@ -14,6 +14,11 @@ 
 
 struct acpi_ctx;
 
+/* ACPI Op/Prefix codes */
+enum {
+	PACKAGE_OP		= 0x12,
+};
+
 /**
  * acpigen_get_current() - Get the current ACPI code output pointer
  *
@@ -65,7 +70,64 @@  void acpigen_emit_stream(struct acpi_ctx *ctx, const char *data, int size);
  */
 void acpigen_emit_string(struct acpi_ctx *ctx, const char *str);
 
+/**
+ * acpigen_write_len_f() - Write a 'forward' length placeholder
+ *
+ * This adds space for a length value in the ACPI stream and pushes the current
+ * position (before the length) on the stack. After calling this you can write
+ * some data and then call acpigen_pop_len() to update the length value.
+ *
+ * Usage:
+ *
+ *    acpigen_write_len_f() ------\
+ *    acpigen_write...()          |
+ *    acpigen_write...()          |
+ *      acpigen_write_len_f() --\ |
+ *      acpigen_write...()      | |
+ *      acpigen_write...()      | |
+ *      acpigen_pop_len() ------/ |
+ *    acpigen_write...()          |
+ *    acpigen_pop_len() ----------/
+ *
+ * @ctx: ACPI context pointer
+ */
 void acpigen_write_len_f(struct acpi_ctx *ctx);
+
+/**
+ * acpigen_pop_len() - Update the previously stacked length placeholder
+ *
+ * Call this after the data for the block gas been written. It updates the
+ * top length value in the stack and pops it off.
+ *
+ * @ctx: ACPI context pointer
+ */
 void acpigen_pop_len(struct acpi_ctx *ctx);
 
+/**
+ * acpigen_write_package() - Start writing a package
+ *
+ * A package collects together a number of elements in the ACPI code. To write
+ * a package use:
+ *
+ * acpigen_write_package(ctx, 3);
+ * ...write things
+ * acpigen_pop_len()
+ *
+ * If you don't know the number of elements in advance, acpigen_write_package()
+ * returns a pointer to the value so you can update it later:
+ *
+ * char *num_elements = acpigen_write_package(ctx, 0);
+ * ...write things
+ * *num_elements += 1;
+ * ...write things
+ * *num_elements += 1;
+ * acpigen_pop_len()
+ *
+ * @ctx: ACPI context pointer
+ * @nr_el: Number of elements (0 if not known)
+ * @returns pointer to the number of elements, which can be updated by the
+ *	caller if needed
+ */
+char *acpigen_write_package(struct acpi_ctx *ctx, int nr_el);
+
 #endif
diff --git a/lib/acpi/acpigen.c b/lib/acpi/acpigen.c
index 8a1c3e8256..ca9e96597e 100644
--- a/lib/acpi/acpigen.c
+++ b/lib/acpi/acpigen.c
@@ -69,6 +69,18 @@  void acpigen_pop_len(struct acpi_ctx *ctx)
 	p[2] = (len >> 12 & 0xff);
 }
 
+char *acpigen_write_package(struct acpi_ctx *ctx, int nr_el)
+{
+	char *p;
+
+	acpigen_emit_byte(ctx, PACKAGE_OP);
+	acpigen_write_len_f(ctx);
+	p = ctx->current;
+	acpigen_emit_byte(ctx, nr_el);
+
+	return p;
+}
+
 void acpigen_emit_stream(struct acpi_ctx *ctx, const char *data, int size)
 {
 	int i;
diff --git a/test/dm/acpigen.c b/test/dm/acpigen.c
index f9c15b7503..be81068759 100644
--- a/test/dm/acpigen.c
+++ b/test/dm/acpigen.c
@@ -394,3 +394,30 @@  static int dm_test_acpi_len(struct unit_test_state *uts)
 	return 0;
 }
 DM_TEST(dm_test_acpi_len, 0);
+
+/* Test emitting a package */
+static int dm_test_acpi_package(struct unit_test_state *uts)
+{
+	struct acpi_ctx *ctx;
+	char *num_elements;
+	u8 *ptr;
+
+	ut_assertok(alloc_context(&ctx));
+
+	ptr = acpigen_get_current(ctx);
+
+	num_elements = acpigen_write_package(ctx, 3);
+	ut_asserteq_ptr(num_elements, ptr + 4);
+
+	/* For easy of testing, just emit a byte, not valid package contents */
+	acpigen_emit_byte(ctx, 0x23);
+	acpigen_pop_len(ctx);
+	ut_asserteq(PACKAGE_OP, ptr[0]);
+	ut_asserteq(5, get_length(ptr + 1));
+	ut_asserteq(3, ptr[4]);
+
+	free_context(&ctx);
+
+	return 0;
+}
+DM_TEST(dm_test_acpi_package, 0);