acpi: Change device properties to work as a tree

There is a second ACPI _DSD document from the UEFI Forum that details
how _DSD style tables can be nested, creating a tree of similarly
formatted tables.  This document is linked from acpi_device.h.

In order to support this the device property interface needs to be
more flexible and build up a tree of properties to write all entries
at once instead of writing each entry as it is generated.

In the end this is a more flexible solution that can support drivers
that need child tables like the DA7219 codec, while only requiring
minor changes to the existing drivers that use the device property
interface.

This was tested on reef (apollolake) and chell (skylake) boards to
ensure that there was no change in the generated SSDT AML.

Change-Id: Ia22e3a5fd3982ffa7c324bee1a8d190d49f853dd
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/15537
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

5 files changed, 345 insertions, 153 deletions

diff --git a/src/arch/x86/acpi_device.c b/src/arch/x86/acpi_device.c
index f8f6a6dbe9..ce31dc8e21 100644
--- a/src/arch/x86/acpi_device.c
+++ b/src/arch/x86/acpi_device.c
@@ -24,14 +24,31 @@
 #include <gpio.h>
 #endif
 
-/*
- * Pointer to length field in device properties package
- * Location is set in dp_header() and length filled in by dp_footer()
- */
-static char *dp_count_ptr;
-
-/* Count of the number of device properties in the current set */
-static char dp_count;
+#define ACPI_DP_UUID		"daffd814-6eba-4d8c-8a91-bc9bbf4aa301"
+#define ACPI_DP_CHILD_UUID	"dbb8e3e6-5886-4ba6-8795-1319f52a966b"
+
+enum acpi_dp_type {
+	ACPI_DP_TYPE_INTEGER,
+	ACPI_DP_TYPE_STRING,
+	ACPI_DP_TYPE_REFERENCE,
+	ACPI_DP_TYPE_TABLE,
+	ACPI_DP_TYPE_ARRAY,
+	ACPI_DP_TYPE_CHILD,
+};
+
+struct acpi_dp {
+	enum acpi_dp_type type;
+	const char *name;
+	struct acpi_dp *next;
+	union {
+		struct acpi_dp *child;
+		struct acpi_dp *array;
+	};
+	union {
+		uint64_t integer;
+		const char *string;
+	};
+};
 
 /* Write empty word value and return pointer to it */
 static void *acpi_device_write_zero_len(void)
@@ -473,39 +490,8 @@ void acpi_device_write_spi(const struct acpi_spi *spi)
 	acpi_device_fill_len(desc_length);
 }
 
-/* Write a header for using _DSD to export Device Properties */
-void acpi_dp_write_header(void)
-{
-	/* Name (_DSD) */
-	acpigen_write_name("_DSD");
-
-	/* Package (2) */
-	acpigen_write_package(2);
-
-	/* ToUUID (ACPI_DP_UUID) */
-	acpigen_write_uuid(ACPI_DP_UUID);
-
-	/* Package (X) */
-	acpigen_emit_byte(0x12);
-	acpigen_write_len_f();
-	dp_count_ptr = acpigen_get_current();
-	acpigen_emit_byte(0); /* Number of elements, filled by dp_footer */
-
-	/* Reset element counter */
-	dp_count = 0;
-}
-
-/* Fill in length values from writing Device Properties */
-void acpi_dp_write_footer(void)
-{
-	/* Patch device property element count */
-	*dp_count_ptr = dp_count;
-
-	acpigen_pop_len(); /* Inner package length */
-	acpigen_pop_len(); /* Outer package length */
-}
-
-void acpi_dp_write_value(const struct acpi_dp *prop)
+static void acpi_dp_write_array(const struct acpi_dp *array);
+static void acpi_dp_write_value(const struct acpi_dp *prop)
 {
 	switch (prop->type) {
 	case ACPI_DP_TYPE_INTEGER:
@@ -515,86 +501,266 @@ void acpi_dp_write_value(const struct acpi_dp *prop)
 		acpigen_write_string(prop->string);
 		break;
 	case ACPI_DP_TYPE_REFERENCE:
+	case ACPI_DP_TYPE_CHILD:
 		acpigen_emit_namestring(prop->string);
 		break;
+	case ACPI_DP_TYPE_ARRAY:
+		acpi_dp_write_array(prop->array);
+		break;
+	default:
+		break;
 	}
 }
 
-/* Write Device Property key with value as an integer */
-void acpi_dp_write_keyval(const char *key, const struct acpi_dp *prop)
+/* Package (2) { "prop->name", VALUE } */
+static void acpi_dp_write_property(const struct acpi_dp *prop)
 {
 	acpigen_write_package(2);
-	acpigen_write_string(key);
+	acpigen_write_string(prop->name);
 	acpi_dp_write_value(prop);
 	acpigen_pop_len();
-	dp_count++;
 }
 
-/* Write Device Property key with value as an integer */
-void acpi_dp_write_integer(const char *key, uint64_t value)
+/* Write array of Device Properties */
+static void acpi_dp_write_array(const struct acpi_dp *array)
 {
-	const struct acpi_dp prop = ACPI_DP_INTEGER(value);
-	acpi_dp_write_keyval(key, &prop);
-}
+	const struct acpi_dp *dp;
+	char *pkg_count;
 
-/* Write Device Property key with value as a string */
-void acpi_dp_write_string(const char *key, const char *value)
-{
-	const struct acpi_dp prop = ACPI_DP_STRING(value);
-	acpi_dp_write_keyval(key, &prop);
+	/* Package element count determined as it is populated */
+	pkg_count = acpigen_write_package(0);
+
+	for (dp = array; dp; dp = dp->next) {
+		acpi_dp_write_value(dp);
+		(*pkg_count)++;
+	}
+
+	acpigen_pop_len();
 }
 
-/* Write Device Property key with value as a reference */
-void acpi_dp_write_reference(const char *key, const char *value)
+static void acpi_dp_free(struct acpi_dp *dp)
 {
-	const struct acpi_dp prop = ACPI_DP_REFERENCE(value);
-	acpi_dp_write_keyval(key, &prop);
+	while (dp) {
+		struct acpi_dp *p = dp->next;
+
+		switch (dp->type) {
+		case ACPI_DP_TYPE_CHILD:
+			acpi_dp_free(dp->child);
+			break;
+		case ACPI_DP_TYPE_ARRAY:
+			acpi_dp_free(dp->array);
+			break;
+		default:
+			break;
+		}
+
+		free(dp);
+		dp = p;
+	}
 }
 
-/* Write array of Device Properties */
-void acpi_dp_write_array(const char *key, const struct acpi_dp *array, int len)
+void acpi_dp_write(struct acpi_dp *table)
 {
-	int i;
-	acpigen_write_package(2);
-	acpigen_write_string(key);
-	acpigen_write_package(len);
-	for (i = 0; i < len; i++)
-		acpi_dp_write_value(&array[i]);
+	struct acpi_dp *dp, *prop;
+	char *dp_count, *prop_count;
+	int child_count = 0;
+
+	if (!table || table->type != ACPI_DP_TYPE_TABLE)
+		return;
+
+	/* Name (name) */
+	acpigen_write_name(table->name);
+
+	/* Device Property list starts with the next entry */
+	prop = table->next;
+
+	/* Package (DP), default to 2 elements (assuming no children) */
+	dp_count = acpigen_write_package(2);
+
+	/* ToUUID (ACPI_DP_UUID) */
+	acpigen_write_uuid(ACPI_DP_UUID);
+
+	/* Package (PROP), element count determined as it is populated */
+	prop_count = acpigen_write_package(0);
+
+	/* Print base properties */
+	for (dp = prop; dp; dp = dp->next) {
+		if (dp->type == ACPI_DP_TYPE_CHILD) {
+			child_count++;
+		} else {
+			(*prop_count)++;
+			acpi_dp_write_property(dp);
+		}
+	}
+
+	/* Package (PROP) length */
 	acpigen_pop_len();
+
+	if (child_count) {
+		/* Update DP package count to 4 */
+		*dp_count = 4;
+
+		/* ToUUID (ACPI_DP_CHILD_UUID) */
+		acpigen_write_uuid(ACPI_DP_CHILD_UUID);
+
+		/* Print child pointer properties */
+		acpigen_write_package(child_count);
+
+		for (dp = prop; dp; dp = dp->next)
+			if (dp->type == ACPI_DP_TYPE_CHILD)
+				acpi_dp_write_property(dp);
+
+		acpigen_pop_len();
+	}
+
+	/* Package (DP) length */
 	acpigen_pop_len();
-	dp_count++;
+
+	/* Recursively parse children into separate tables */
+	for (dp = prop; dp; dp = dp->next)
+		if (dp->type == ACPI_DP_TYPE_CHILD)
+			acpi_dp_write(dp->child);
+
+	/* Clean up */
+	acpi_dp_free(table);
+}
+
+static struct acpi_dp *acpi_dp_new(struct acpi_dp *dp, enum acpi_dp_type type,
+				   const char *name)
+{
+	struct acpi_dp *new;
+
+	new = malloc(sizeof(struct acpi_dp));
+	if (!new)
+		return NULL;
+
+	memset(new, 0, sizeof(*new));
+	new->type = type;
+	new->name = name;
+
+	if (dp) {
+		/* Add to end of property list */
+		while (dp->next)
+			dp = dp->next;
+		dp->next = new;
+	}
+
+	return new;
+}
+
+struct acpi_dp *acpi_dp_new_table(const char *name)
+{
+	return acpi_dp_new(NULL, ACPI_DP_TYPE_TABLE, name);
+}
+
+struct acpi_dp *acpi_dp_add_integer(struct acpi_dp *dp, const char *name,
+				    uint64_t value)
+{
+	struct acpi_dp *new = acpi_dp_new(dp, ACPI_DP_TYPE_INTEGER, name);
+
+	if (new)
+		new->integer = value;
+
+	return new;
+}
+
+struct acpi_dp *acpi_dp_add_string(struct acpi_dp *dp, const char *name,
+				   const char *string)
+{
+	struct acpi_dp *new = acpi_dp_new(dp, ACPI_DP_TYPE_STRING, name);
+
+	if (new)
+		new->string = string;
+
+	return new;
+}
+
+struct acpi_dp *acpi_dp_add_reference(struct acpi_dp *dp, const char *name,
+				      const char *reference)
+{
+	struct acpi_dp *new = acpi_dp_new(dp, ACPI_DP_TYPE_REFERENCE, name);
+
+	if (new)
+		new->string = reference;
+
+	return new;
 }
 
-/* Write array of Device Properties with values as integers */
-void acpi_dp_write_integer_array(const char *key, uint64_t *array, int len)
+struct acpi_dp *acpi_dp_add_child(struct acpi_dp *dp, const char *name,
+				  struct acpi_dp *child)
 {
+	struct acpi_dp *new;
+
+	if (!child || child->type != ACPI_DP_TYPE_TABLE)
+		return NULL;
+
+	new = acpi_dp_new(dp, ACPI_DP_TYPE_CHILD, name);
+	if (new) {
+		new->child = child;
+		new->string = child->name;
+	}
+
+	return new;
+}
+
+struct acpi_dp *acpi_dp_add_array(struct acpi_dp *dp, struct acpi_dp *array)
+{
+	struct acpi_dp *new;
+
+	if (!array || array->type != ACPI_DP_TYPE_TABLE)
+		return NULL;
+
+	new = acpi_dp_new(dp, ACPI_DP_TYPE_ARRAY, array->name);
+	if (new)
+		new->array = array;
+
+	return new;
+}
+
+struct acpi_dp *acpi_dp_add_integer_array(struct acpi_dp *dp, const char *name,
+					  uint64_t *array, int len)
+{
+	struct acpi_dp *dp_array;
 	int i;
-	acpigen_write_package(2);
-	acpigen_write_string(key);
-	acpigen_write_package(len);
+
+	if (len <= 0)
+		return NULL;
+
+	dp_array = acpi_dp_new_table(name);
+	if (!dp_array)
+		return NULL;
+
 	for (i = 0; i < len; i++)
-		acpigen_write_integer(array[i]);
-	acpigen_pop_len();
-	acpigen_pop_len();
-	dp_count++;
+		if (!acpi_dp_add_integer(dp_array, NULL, array[i]))
+			break;
+
+	acpi_dp_add_array(dp, dp_array);
+
+	return dp_array;
 }
 
-/*
- * Device Properties for GPIO binding
- * linux/Documentation/acpi/gpio-properties.txt
- */
-void acpi_dp_write_gpio(const char *key, const char *ref, int index,
-			int pin, int active_low)
+struct acpi_dp *acpi_dp_add_gpio(struct acpi_dp *dp, const char *name,
+				 const char *ref, int index, int pin,
+				 int active_low)
 {
-	const struct acpi_dp gpio_prop[] = {
-		/* The device that has _CRS containing GpioIo()/GpioInt() */
-		ACPI_DP_REFERENCE(ref),
-		/* Index of the GPIO resource in _CRS starting from zero */
-		ACPI_DP_INTEGER(index),
-		/* Pin in the GPIO resource, typically zero */
-		ACPI_DP_INTEGER(pin),
-		/* Set if pin is active low */
-		ACPI_DP_INTEGER(active_low)
-	};
-	acpi_dp_write_array(key, gpio_prop, ARRAY_SIZE(gpio_prop));
+	struct acpi_dp *gpio = acpi_dp_new_table(name);
+
+	if (!gpio)
+		return NULL;
+
+	/* The device that has _CRS containing GpioIO()/GpioInt() */
+	acpi_dp_add_reference(gpio, NULL, ref);
+
+	/* Index of the GPIO resource in _CRS starting from zero */
+	acpi_dp_add_integer(gpio, NULL, index);
+
+	/* Pin in the GPIO resource, typically zero */
+	acpi_dp_add_integer(gpio, NULL, pin);
+
+	/* Set if pin is active low */
+	acpi_dp_add_integer(gpio, NULL, active_low);
+
+	acpi_dp_add_array(dp, gpio);
+
+	return gpio;
 }
diff --git a/src/arch/x86/include/arch/acpi_device.h b/src/arch/x86/include/arch/acpi_device.h
index 65f49b2cb0..4b3a469199 100644
--- a/src/arch/x86/include/arch/acpi_device.h
+++ b/src/arch/x86/include/arch/acpi_device.h
@@ -229,63 +229,85 @@ struct acpi_spi {
 void acpi_device_write_spi(const struct acpi_spi *spi);
 
 /*
- * Device Properties with _DSD
- * http://uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf
- */
-
-#define ACPI_DP_UUID "daffd814-6eba-4d8c-8a91-bc9bbf4aa301"
-
-enum acpi_dp_type {
-	ACPI_DP_TYPE_INTEGER,
-	ACPI_DP_TYPE_STRING,
-	ACPI_DP_TYPE_REFERENCE,
-};
-
-struct acpi_dp {
-	enum acpi_dp_type type;
-	union {
-		uint64_t integer;
-		const char *string;
-	};
-};
-
-#define ACPI_DP_INTEGER(x)   { .type = ACPI_DP_TYPE_INTEGER, .integer = x }
-#define ACPI_DP_STRING(x)    { .type = ACPI_DP_TYPE_STRING, .string = x }
-#define ACPI_DP_REFERENCE(x) { .type = ACPI_DP_TYPE_REFERENCE, .string = x }
-
-/*
  * Writing Device Properties objects via _DSD
+ *
+ * http://uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf
+ * http://uefi.org/sites/default/files/resources/_DSD-hierarchical-data-extension-UUID-v1.pdf
+ *
+ * The Device Property Hierarchy can be multiple levels deep with multiple
+ * children possible in each level.  In order to support this flexibility
+ * the device property hierarchy must be built up before being written out.
+ *
+ * For example:
+ *
+ * // Child table with string and integer
+ * struct acpi_dp *child = acpi_dp_new_table("CHLD");
+ * acpi_dp_add_string(child, "childstring", "CHILD");
+ * acpi_dp_add_integer(child, "childint", 100);
+ *
+ * // _DSD table with integer and gpio and child pointer
+ * struct acpi_dp *dsd = acpi_dp_new_table("_DSD");
+ * acpi_dp_add_integer(dsd, "number1", 1);
+ * acpi_dp_add_gpio(dsd, "gpio", "\_SB.PCI0.GPIO", 0, 0, 1);
+ * acpi_dp_add_child(dsd, "child", child);
+ *
+ * // Write entries into SSDT and clean up resources
+ * acpi_dp_write(dsd);
+ *
+ * Name(_DSD, Package() {
+ *   ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301")
+ *   Package() {
+ *     Package() { "gpio", Package() { \_SB.PCI0.GPIO, 0, 0, 0 } }
+ *     Package() { "number1", 1 }
+ *   }
+ *   ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b")
+ *   Package() {
+ *     Package() { "child", CHLD }
+ *   }
+ * }
+ * Name(CHLD, Package() {
+ *   ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301")
+ *   Package() {
+ *     Package() { "childstring", "CHILD" }
+ *     Package() { "childint", 100 }
+ *   }
+ * }
  */
 
-/* Start a set of Device Properties with _DSD and UUID */
-void acpi_dp_write_header(void);
+struct acpi_dp;
 
-/* End the Device Properties set and fill in length values */
-void acpi_dp_write_footer(void);
+/* Start a new Device Property table with provided ACPI reference */
+struct acpi_dp *acpi_dp_new_table(const char *ref);
 
-/* Write a Device Property value, but not the key */
-void acpi_dp_write_value(const struct acpi_dp *prop);
+/* Add integer Device Property */
+struct acpi_dp *acpi_dp_add_integer(struct acpi_dp *dp, const char *name,
+				    uint64_t value);
 
-/* Write a Device Property, both key and value */
-void acpi_dp_write_keyval(const char *key, const struct acpi_dp *prop);
+/* Add string Device Property */
+struct acpi_dp *acpi_dp_add_string(struct acpi_dp *dp, const char *name,
+				   const char *string);
 
-/* Write an integer as a Device Property */
-void acpi_dp_write_integer(const char *key, uint64_t value);
+/* Add ACPI reference Device Property */
+struct acpi_dp *acpi_dp_add_reference(struct acpi_dp *dp, const char *name,
+				      const char *reference);
 
-/* Write a string as a Device Property */
-void acpi_dp_write_string(const char *key, const char *value);
+/* Add an array of Device Properties */
+struct acpi_dp *acpi_dp_add_array(struct acpi_dp *dp, struct acpi_dp *array);
 
-/* Write an ACPI reference as a Device Property */
-void acpi_dp_write_reference(const char *key, const char *value);
+/* Add an array of integers Device Property */
+struct acpi_dp *acpi_dp_add_integer_array(struct acpi_dp *dp, const char *name,
+					  uint64_t *array, int len);
 
-/* Write an array of Device Properties */
-void acpi_dp_write_array(const char *key, const struct acpi_dp *array, int len);
+/* Add a GPIO binding Device Property */
+struct acpi_dp *acpi_dp_add_gpio(struct acpi_dp *dp, const char *name,
+				 const char *ref, int index, int pin,
+				 int active_low);
 
-/* Write an array of integers as Device Properties */
-void acpi_dp_write_integer_array(const char *key, uint64_t *array, int len);
+/* Add a child table of Device Properties */
+struct acpi_dp *acpi_dp_add_child(struct acpi_dp *dp, const char *name,
+				  struct acpi_dp *child);
 
-/* Write a GPIO binding Device Property */
-void acpi_dp_write_gpio(const char *key, const char *ref, int index,
-			int pin, int active_low);
+/* Write Device Property hierarchy and clean up resources */
+void acpi_dp_write(struct acpi_dp *table);
 
 #endif
diff --git a/src/drivers/generic/max98357a/max98357a.c b/src/drivers/generic/max98357a/max98357a.c
index 0d522d45c0..25e5104129 100644
--- a/src/drivers/generic/max98357a/max98357a.c
+++ b/src/drivers/generic/max98357a/max98357a.c
@@ -32,6 +32,7 @@ static void max98357a_fill_ssdt(struct device *dev)
 {
 	struct drivers_generic_max98357a_config *config = dev->chip_info;
 	const char *path;
+	struct acpi_dp *dp;
 
 	if (!dev->enabled || !config)
 		return;
@@ -51,12 +52,12 @@ static void max98357a_fill_ssdt(struct device *dev)
 	acpigen_write_resourcetemplate_footer();
 
 	/* _DSD for devicetree properties */
-	acpi_dp_write_header();
 	/* This points to the first pin in the first gpio entry in _CRS */
 	path = acpi_device_path(dev);
-	acpi_dp_write_gpio("sdmode-gpio", path, 0, 0, 0);
-	acpi_dp_write_integer("sdmode-delay", config->sdmode_delay);
-	acpi_dp_write_footer();
+	dp = acpi_dp_new_table("_DSD");
+	acpi_dp_add_gpio(dp, "sdmode-gpio", path, 0, 0, 0);
+	acpi_dp_add_integer(dp, "sdmode-delay", config->sdmode_delay);
+	acpi_dp_write(dp);
 
 	acpigen_pop_len(); /* Device */
 	acpigen_pop_len(); /* Scope */
diff --git a/src/drivers/i2c/nau8825/nau8825.c b/src/drivers/i2c/nau8825/nau8825.c
index 71aaceaf15..a86eff41f3 100644
--- a/src/drivers/i2c/nau8825/nau8825.c
+++ b/src/drivers/i2c/nau8825/nau8825.c
@@ -28,7 +28,9 @@
 
 #define NAU8825_ACPI_NAME	"NAU8"
 #define NAU8825_ACPI_HID	"10508825"
-#define NAU8825_DP_INT(key,val)	acpi_dp_write_integer("nuvoton," key, (val))
+
+#define NAU8825_DP_INT(key,val) \
+	acpi_dp_add_integer(dp, "nuvoton," key, (val))
 
 static void nau8825_fill_ssdt(struct device *dev)
 {
@@ -40,6 +42,7 @@ static void nau8825_fill_ssdt(struct device *dev)
 		.speed = config->bus_speed ? : I2C_SPEED_FAST,
 		.resource = scope,
 	};
+	struct acpi_dp *dp = NULL;
 
 	if (!dev->enabled || !scope)
 		return;
@@ -62,7 +65,7 @@ static void nau8825_fill_ssdt(struct device *dev)
 	acpigen_write_resourcetemplate_footer();
 
 	/* Device Properties */
-	acpi_dp_write_header();
+	dp = acpi_dp_new_table("_DSD");
 	NAU8825_DP_INT("jkdet-enable", config->jkdet_enable);
 	NAU8825_DP_INT("jkdet-pull-enable", config->jkdet_pull_enable);
 	NAU8825_DP_INT("jkdet-pull-up", config->jkdet_pull_up);
@@ -77,10 +80,9 @@ static void nau8825_fill_ssdt(struct device *dev)
 	NAU8825_DP_INT("jack-insert-debounce", config->jack_insert_debounce);
 	NAU8825_DP_INT("jack-eject-deboune", config->jack_eject_debounce);
 	NAU8825_DP_INT("sar-threshold-num", config->sar_threshold_num);
-	acpi_dp_write_integer_array("nuvoton,sar-threshold",
-				    config->sar_threshold,
-				    config->sar_threshold_num);
-	acpi_dp_write_footer();
+	acpi_dp_add_integer_array(dp, "nuvoton,sar-threshold",
+			  config->sar_threshold, config->sar_threshold_num);
+	acpi_dp_write(dp);
 
 	acpigen_pop_len(); /* Device */
 	acpigen_pop_len(); /* Scope */
diff --git a/src/soc/intel/skylake/sd.c b/src/soc/intel/skylake/sd.c
index 80adb9c467..a75cf635d3 100644
--- a/src/soc/intel/skylake/sd.c
+++ b/src/soc/intel/skylake/sd.c
@@ -38,6 +38,7 @@ static void sd_fill_ssdt(struct device *dev)
 		.pin_count = 1,
 		.pins = { config->sdcard_cd_gpio_default }
 	};
+	struct acpi_dp *dp;
 
 	if (!dev->enabled)
 		return;
@@ -62,9 +63,9 @@ static void sd_fill_ssdt(struct device *dev)
 	acpigen_write_resourcetemplate_footer();
 
 	/* Bind the cd-gpio name to the GpioInt() resource */
-	acpi_dp_write_header();
-	acpi_dp_write_gpio("cd-gpio", path, 0, 0, 1);
-	acpi_dp_write_footer();
+	dp = acpi_dp_new_table("_DSD");
+	acpi_dp_add_gpio(dp, "cd-gpio", path, 0, 0, 1);
+	acpi_dp_write(dp);
 
 	acpigen_pop_len();
 }