[2/9] drm/i915/bios: store child devices in a list
diff mbox series

Message ID 3e72da0b412354ed8be6719df55b0e0cc4caa61a.1573227240.git.jani.nikula@intel.com
State New
Headers show
Series
  • drm/i915/dsi: enable DSC
Related show

Commit Message

Jani Nikula Nov. 8, 2019, 3:39 p.m. UTC
Using the array is getting clumsy. Make things a bit more dynamic.

Remove early returns on not having child devices when the end result
after "iterating" the empty list would be the same.

v3:
- use list_add_tail to not reverse the child device list (Ville)

v2:
- stick to previous naming of child devices (Ville)
- use kzalloc, handle failure
- initialize list head earlier to keep intel_bios_driver_remove() safe

Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/i915/display/intel_bios.c | 123 ++++++++++------------
 drivers/gpu/drm/i915/i915_drv.h           |   3 +-
 2 files changed, 58 insertions(+), 68 deletions(-)

Comments

Jani Nikula Nov. 12, 2019, 4:14 p.m. UTC | #1
On Fri, 08 Nov 2019, Jani Nikula <jani.nikula@intel.com> wrote:
> Using the array is getting clumsy. Make things a bit more dynamic.
>
> Remove early returns on not having child devices when the end result
> after "iterating" the empty list would be the same.
>
> v3:
> - use list_add_tail to not reverse the child device list (Ville)
>
> v2:
> - stick to previous naming of child devices (Ville)
> - use kzalloc, handle failure
> - initialize list head earlier to keep intel_bios_driver_remove() safe
>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Pushed this one, thanks for the review.

BR,
Jani.

> ---
>  drivers/gpu/drm/i915/display/intel_bios.c | 123 ++++++++++------------
>  drivers/gpu/drm/i915/i915_drv.h           |   3 +-
>  2 files changed, 58 insertions(+), 68 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
> index c19b234bebe6..7c0ca733bef8 100644
> --- a/drivers/gpu/drm/i915/display/intel_bios.c
> +++ b/drivers/gpu/drm/i915/display/intel_bios.c
> @@ -58,6 +58,12 @@
>   * that.
>   */
>  
> +/* Wrapper for VBT child device config */
> +struct display_device_data {
> +	struct child_device_config child;
> +	struct list_head node;
> +};
> +
>  #define	SLAVE_ADDR1	0x70
>  #define	SLAVE_ADDR2	0x72
>  
> @@ -449,8 +455,9 @@ static void
>  parse_sdvo_device_mapping(struct drm_i915_private *dev_priv, u8 bdb_version)
>  {
>  	struct sdvo_device_mapping *mapping;
> +	const struct display_device_data *devdata;
>  	const struct child_device_config *child;
> -	int i, count = 0;
> +	int count = 0;
>  
>  	/*
>  	 * Only parse SDVO mappings on gens that could have SDVO. This isn't
> @@ -461,8 +468,8 @@ parse_sdvo_device_mapping(struct drm_i915_private *dev_priv, u8 bdb_version)
>  		return;
>  	}
>  
> -	for (i = 0, count = 0; i < dev_priv->vbt.child_dev_num; i++) {
> -		child = dev_priv->vbt.child_dev + i;
> +	list_for_each_entry(devdata, &dev_priv->vbt.display_devices, node) {
> +		child = &devdata->child;
>  
>  		if (child->slave_addr != SLAVE_ADDR1 &&
>  		    child->slave_addr != SLAVE_ADDR2) {
> @@ -1572,8 +1579,7 @@ static void parse_ddi_port(struct drm_i915_private *dev_priv,
>  
>  static void parse_ddi_ports(struct drm_i915_private *dev_priv, u8 bdb_version)
>  {
> -	const struct child_device_config *child;
> -	int i;
> +	const struct display_device_data *devdata;
>  
>  	if (!HAS_DDI(dev_priv) && !IS_CHERRYVIEW(dev_priv))
>  		return;
> @@ -1581,11 +1587,8 @@ static void parse_ddi_ports(struct drm_i915_private *dev_priv, u8 bdb_version)
>  	if (bdb_version < 155)
>  		return;
>  
> -	for (i = 0; i < dev_priv->vbt.child_dev_num; i++) {
> -		child = dev_priv->vbt.child_dev + i;
> -
> -		parse_ddi_port(dev_priv, child, bdb_version);
> -	}
> +	list_for_each_entry(devdata, &dev_priv->vbt.display_devices, node)
> +		parse_ddi_port(dev_priv, &devdata->child, bdb_version);
>  }
>  
>  static void
> @@ -1593,8 +1596,9 @@ parse_general_definitions(struct drm_i915_private *dev_priv,
>  			  const struct bdb_header *bdb)
>  {
>  	const struct bdb_general_definitions *defs;
> +	struct display_device_data *devdata;
>  	const struct child_device_config *child;
> -	int i, child_device_num, count;
> +	int i, child_device_num;
>  	u8 expected_size;
>  	u16 block_size;
>  	int bus_pin;
> @@ -1650,26 +1654,7 @@ parse_general_definitions(struct drm_i915_private *dev_priv,
>  
>  	/* get the number of child device */
>  	child_device_num = (block_size - sizeof(*defs)) / defs->child_dev_size;
> -	count = 0;
> -	/* get the number of child device that is present */
> -	for (i = 0; i < child_device_num; i++) {
> -		child = child_device_ptr(defs, i);
> -		if (!child->device_type)
> -			continue;
> -		count++;
> -	}
> -	if (!count) {
> -		DRM_DEBUG_KMS("no child dev is parsed from VBT\n");
> -		return;
> -	}
> -	dev_priv->vbt.child_dev = kcalloc(count, sizeof(*child), GFP_KERNEL);
> -	if (!dev_priv->vbt.child_dev) {
> -		DRM_DEBUG_KMS("No memory space for child device\n");
> -		return;
> -	}
>  
> -	dev_priv->vbt.child_dev_num = count;
> -	count = 0;
>  	for (i = 0; i < child_device_num; i++) {
>  		child = child_device_ptr(defs, i);
>  		if (!child->device_type)
> @@ -1678,15 +1663,23 @@ parse_general_definitions(struct drm_i915_private *dev_priv,
>  		DRM_DEBUG_KMS("Found VBT child device with type 0x%x\n",
>  			      child->device_type);
>  
> +		devdata = kzalloc(sizeof(*devdata), GFP_KERNEL);
> +		if (!devdata)
> +			break;
> +
>  		/*
>  		 * Copy as much as we know (sizeof) and is available
> -		 * (child_dev_size) of the child device. Accessing the data must
> -		 * depend on VBT version.
> +		 * (child_dev_size) of the child device config. Accessing the
> +		 * data must depend on VBT version.
>  		 */
> -		memcpy(dev_priv->vbt.child_dev + count, child,
> +		memcpy(&devdata->child, child,
>  		       min_t(size_t, defs->child_dev_size, sizeof(*child)));
> -		count++;
> +
> +		list_add_tail(&devdata->node, &dev_priv->vbt.display_devices);
>  	}
> +
> +	if (list_empty(&dev_priv->vbt.display_devices))
> +		DRM_DEBUG_KMS("no child dev is parsed from VBT\n");
>  }
>  
>  /* Common defaults which may be overridden by VBT. */
> @@ -1836,6 +1829,8 @@ void intel_bios_init(struct drm_i915_private *dev_priv)
>  	const struct bdb_header *bdb;
>  	u8 __iomem *bios = NULL;
>  
> +	INIT_LIST_HEAD(&dev_priv->vbt.display_devices);
> +
>  	if (!HAS_DISPLAY(dev_priv) || !INTEL_DISPLAY_ENABLED(dev_priv)) {
>  		DRM_DEBUG_KMS("Skipping VBT init due to disabled display.\n");
>  		return;
> @@ -1895,9 +1890,13 @@ void intel_bios_init(struct drm_i915_private *dev_priv)
>   */
>  void intel_bios_driver_remove(struct drm_i915_private *dev_priv)
>  {
> -	kfree(dev_priv->vbt.child_dev);
> -	dev_priv->vbt.child_dev = NULL;
> -	dev_priv->vbt.child_dev_num = 0;
> +	struct display_device_data *devdata, *n;
> +
> +	list_for_each_entry_safe(devdata, n, &dev_priv->vbt.display_devices, node) {
> +		list_del(&devdata->node);
> +		kfree(devdata);
> +	}
> +
>  	kfree(dev_priv->vbt.sdvo_lvds_vbt_mode);
>  	dev_priv->vbt.sdvo_lvds_vbt_mode = NULL;
>  	kfree(dev_priv->vbt.lfp_lvds_vbt_mode);
> @@ -1921,17 +1920,18 @@ void intel_bios_driver_remove(struct drm_i915_private *dev_priv)
>   */
>  bool intel_bios_is_tv_present(struct drm_i915_private *dev_priv)
>  {
> +	const struct display_device_data *devdata;
>  	const struct child_device_config *child;
> -	int i;
>  
>  	if (!dev_priv->vbt.int_tv_support)
>  		return false;
>  
> -	if (!dev_priv->vbt.child_dev_num)
> +	if (list_empty(&dev_priv->vbt.display_devices))
>  		return true;
>  
> -	for (i = 0; i < dev_priv->vbt.child_dev_num; i++) {
> -		child = dev_priv->vbt.child_dev + i;
> +	list_for_each_entry(devdata, &dev_priv->vbt.display_devices, node) {
> +		child = &devdata->child;
> +
>  		/*
>  		 * If the device type is not TV, continue.
>  		 */
> @@ -1963,14 +1963,14 @@ bool intel_bios_is_tv_present(struct drm_i915_private *dev_priv)
>   */
>  bool intel_bios_is_lvds_present(struct drm_i915_private *dev_priv, u8 *i2c_pin)
>  {
> +	const struct display_device_data *devdata;
>  	const struct child_device_config *child;
> -	int i;
>  
> -	if (!dev_priv->vbt.child_dev_num)
> +	if (list_empty(&dev_priv->vbt.display_devices))
>  		return true;
>  
> -	for (i = 0; i < dev_priv->vbt.child_dev_num; i++) {
> -		child = dev_priv->vbt.child_dev + i;
> +	list_for_each_entry(devdata, &dev_priv->vbt.display_devices, node) {
> +		child = &devdata->child;
>  
>  		/* If the device type is not LFP, continue.
>  		 * We have to check both the new identifiers as well as the
> @@ -2012,6 +2012,7 @@ bool intel_bios_is_lvds_present(struct drm_i915_private *dev_priv, u8 *i2c_pin)
>   */
>  bool intel_bios_is_port_present(struct drm_i915_private *dev_priv, enum port port)
>  {
> +	const struct display_device_data *devdata;
>  	const struct child_device_config *child;
>  	static const struct {
>  		u16 dp, hdmi;
> @@ -2022,7 +2023,6 @@ bool intel_bios_is_port_present(struct drm_i915_private *dev_priv, enum port por
>  		[PORT_E] = { DVO_PORT_DPE, DVO_PORT_HDMIE, },
>  		[PORT_F] = { DVO_PORT_DPF, DVO_PORT_HDMIF, },
>  	};
> -	int i;
>  
>  	if (HAS_DDI(dev_priv)) {
>  		const struct ddi_vbt_port_info *port_info =
> @@ -2037,11 +2037,8 @@ bool intel_bios_is_port_present(struct drm_i915_private *dev_priv, enum port por
>  	if (WARN_ON(port == PORT_A) || port >= ARRAY_SIZE(port_mapping))
>  		return false;
>  
> -	if (!dev_priv->vbt.child_dev_num)
> -		return false;
> -
> -	for (i = 0; i < dev_priv->vbt.child_dev_num; i++) {
> -		child = dev_priv->vbt.child_dev + i;
> +	list_for_each_entry(devdata, &dev_priv->vbt.display_devices, node) {
> +		child = &devdata->child;
>  
>  		if ((child->dvo_port == port_mapping[port].dp ||
>  		     child->dvo_port == port_mapping[port].hdmi) &&
> @@ -2062,6 +2059,7 @@ bool intel_bios_is_port_present(struct drm_i915_private *dev_priv, enum port por
>   */
>  bool intel_bios_is_port_edp(struct drm_i915_private *dev_priv, enum port port)
>  {
> +	const struct display_device_data *devdata;
>  	const struct child_device_config *child;
>  	static const short port_mapping[] = {
>  		[PORT_B] = DVO_PORT_DPB,
> @@ -2070,16 +2068,12 @@ bool intel_bios_is_port_edp(struct drm_i915_private *dev_priv, enum port port)
>  		[PORT_E] = DVO_PORT_DPE,
>  		[PORT_F] = DVO_PORT_DPF,
>  	};
> -	int i;
>  
>  	if (HAS_DDI(dev_priv))
>  		return dev_priv->vbt.ddi_port_info[port].supports_edp;
>  
> -	if (!dev_priv->vbt.child_dev_num)
> -		return false;
> -
> -	for (i = 0; i < dev_priv->vbt.child_dev_num; i++) {
> -		child = dev_priv->vbt.child_dev + i;
> +	list_for_each_entry(devdata, &dev_priv->vbt.display_devices, node) {
> +		child = &devdata->child;
>  
>  		if (child->dvo_port == port_mapping[port] &&
>  		    (child->device_type & DEVICE_TYPE_eDP_BITS) ==
> @@ -2128,13 +2122,10 @@ static bool child_dev_is_dp_dual_mode(const struct child_device_config *child,
>  bool intel_bios_is_port_dp_dual_mode(struct drm_i915_private *dev_priv,
>  				     enum port port)
>  {
> -	const struct child_device_config *child;
> -	int i;
> +	const struct display_device_data *devdata;
>  
> -	for (i = 0; i < dev_priv->vbt.child_dev_num; i++) {
> -		child = dev_priv->vbt.child_dev + i;
> -
> -		if (child_dev_is_dp_dual_mode(child, port))
> +	list_for_each_entry(devdata, &dev_priv->vbt.display_devices, node) {
> +		if (child_dev_is_dp_dual_mode(&devdata->child, port))
>  			return true;
>  	}
>  
> @@ -2151,12 +2142,12 @@ bool intel_bios_is_port_dp_dual_mode(struct drm_i915_private *dev_priv,
>  bool intel_bios_is_dsi_present(struct drm_i915_private *dev_priv,
>  			       enum port *port)
>  {
> +	const struct display_device_data *devdata;
>  	const struct child_device_config *child;
>  	u8 dvo_port;
> -	int i;
>  
> -	for (i = 0; i < dev_priv->vbt.child_dev_num; i++) {
> -		child = dev_priv->vbt.child_dev + i;
> +	list_for_each_entry(devdata, &dev_priv->vbt.display_devices, node) {
> +		child = &devdata->child;
>  
>  		if (!(child->device_type & DEVICE_TYPE_MIPI_OUTPUT))
>  			continue;
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 67bdfe6de3fa..2c0674a86dd8 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -720,8 +720,7 @@ struct intel_vbt_data {
>  
>  	int crt_ddc_pin;
>  
> -	int child_dev_num;
> -	struct child_device_config *child_dev;
> +	struct list_head display_devices;
>  
>  	struct ddi_vbt_port_info ddi_port_info[I915_MAX_PORTS];
>  	struct sdvo_device_mapping sdvo_mappings[2];

Patch
diff mbox series

diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
index c19b234bebe6..7c0ca733bef8 100644
--- a/drivers/gpu/drm/i915/display/intel_bios.c
+++ b/drivers/gpu/drm/i915/display/intel_bios.c
@@ -58,6 +58,12 @@ 
  * that.
  */
 
+/* Wrapper for VBT child device config */
+struct display_device_data {
+	struct child_device_config child;
+	struct list_head node;
+};
+
 #define	SLAVE_ADDR1	0x70
 #define	SLAVE_ADDR2	0x72
 
@@ -449,8 +455,9 @@  static void
 parse_sdvo_device_mapping(struct drm_i915_private *dev_priv, u8 bdb_version)
 {
 	struct sdvo_device_mapping *mapping;
+	const struct display_device_data *devdata;
 	const struct child_device_config *child;
-	int i, count = 0;
+	int count = 0;
 
 	/*
 	 * Only parse SDVO mappings on gens that could have SDVO. This isn't
@@ -461,8 +468,8 @@  parse_sdvo_device_mapping(struct drm_i915_private *dev_priv, u8 bdb_version)
 		return;
 	}
 
-	for (i = 0, count = 0; i < dev_priv->vbt.child_dev_num; i++) {
-		child = dev_priv->vbt.child_dev + i;
+	list_for_each_entry(devdata, &dev_priv->vbt.display_devices, node) {
+		child = &devdata->child;
 
 		if (child->slave_addr != SLAVE_ADDR1 &&
 		    child->slave_addr != SLAVE_ADDR2) {
@@ -1572,8 +1579,7 @@  static void parse_ddi_port(struct drm_i915_private *dev_priv,
 
 static void parse_ddi_ports(struct drm_i915_private *dev_priv, u8 bdb_version)
 {
-	const struct child_device_config *child;
-	int i;
+	const struct display_device_data *devdata;
 
 	if (!HAS_DDI(dev_priv) && !IS_CHERRYVIEW(dev_priv))
 		return;
@@ -1581,11 +1587,8 @@  static void parse_ddi_ports(struct drm_i915_private *dev_priv, u8 bdb_version)
 	if (bdb_version < 155)
 		return;
 
-	for (i = 0; i < dev_priv->vbt.child_dev_num; i++) {
-		child = dev_priv->vbt.child_dev + i;
-
-		parse_ddi_port(dev_priv, child, bdb_version);
-	}
+	list_for_each_entry(devdata, &dev_priv->vbt.display_devices, node)
+		parse_ddi_port(dev_priv, &devdata->child, bdb_version);
 }
 
 static void
@@ -1593,8 +1596,9 @@  parse_general_definitions(struct drm_i915_private *dev_priv,
 			  const struct bdb_header *bdb)
 {
 	const struct bdb_general_definitions *defs;
+	struct display_device_data *devdata;
 	const struct child_device_config *child;
-	int i, child_device_num, count;
+	int i, child_device_num;
 	u8 expected_size;
 	u16 block_size;
 	int bus_pin;
@@ -1650,26 +1654,7 @@  parse_general_definitions(struct drm_i915_private *dev_priv,
 
 	/* get the number of child device */
 	child_device_num = (block_size - sizeof(*defs)) / defs->child_dev_size;
-	count = 0;
-	/* get the number of child device that is present */
-	for (i = 0; i < child_device_num; i++) {
-		child = child_device_ptr(defs, i);
-		if (!child->device_type)
-			continue;
-		count++;
-	}
-	if (!count) {
-		DRM_DEBUG_KMS("no child dev is parsed from VBT\n");
-		return;
-	}
-	dev_priv->vbt.child_dev = kcalloc(count, sizeof(*child), GFP_KERNEL);
-	if (!dev_priv->vbt.child_dev) {
-		DRM_DEBUG_KMS("No memory space for child device\n");
-		return;
-	}
 
-	dev_priv->vbt.child_dev_num = count;
-	count = 0;
 	for (i = 0; i < child_device_num; i++) {
 		child = child_device_ptr(defs, i);
 		if (!child->device_type)
@@ -1678,15 +1663,23 @@  parse_general_definitions(struct drm_i915_private *dev_priv,
 		DRM_DEBUG_KMS("Found VBT child device with type 0x%x\n",
 			      child->device_type);
 
+		devdata = kzalloc(sizeof(*devdata), GFP_KERNEL);
+		if (!devdata)
+			break;
+
 		/*
 		 * Copy as much as we know (sizeof) and is available
-		 * (child_dev_size) of the child device. Accessing the data must
-		 * depend on VBT version.
+		 * (child_dev_size) of the child device config. Accessing the
+		 * data must depend on VBT version.
 		 */
-		memcpy(dev_priv->vbt.child_dev + count, child,
+		memcpy(&devdata->child, child,
 		       min_t(size_t, defs->child_dev_size, sizeof(*child)));
-		count++;
+
+		list_add_tail(&devdata->node, &dev_priv->vbt.display_devices);
 	}
+
+	if (list_empty(&dev_priv->vbt.display_devices))
+		DRM_DEBUG_KMS("no child dev is parsed from VBT\n");
 }
 
 /* Common defaults which may be overridden by VBT. */
@@ -1836,6 +1829,8 @@  void intel_bios_init(struct drm_i915_private *dev_priv)
 	const struct bdb_header *bdb;
 	u8 __iomem *bios = NULL;
 
+	INIT_LIST_HEAD(&dev_priv->vbt.display_devices);
+
 	if (!HAS_DISPLAY(dev_priv) || !INTEL_DISPLAY_ENABLED(dev_priv)) {
 		DRM_DEBUG_KMS("Skipping VBT init due to disabled display.\n");
 		return;
@@ -1895,9 +1890,13 @@  void intel_bios_init(struct drm_i915_private *dev_priv)
  */
 void intel_bios_driver_remove(struct drm_i915_private *dev_priv)
 {
-	kfree(dev_priv->vbt.child_dev);
-	dev_priv->vbt.child_dev = NULL;
-	dev_priv->vbt.child_dev_num = 0;
+	struct display_device_data *devdata, *n;
+
+	list_for_each_entry_safe(devdata, n, &dev_priv->vbt.display_devices, node) {
+		list_del(&devdata->node);
+		kfree(devdata);
+	}
+
 	kfree(dev_priv->vbt.sdvo_lvds_vbt_mode);
 	dev_priv->vbt.sdvo_lvds_vbt_mode = NULL;
 	kfree(dev_priv->vbt.lfp_lvds_vbt_mode);
@@ -1921,17 +1920,18 @@  void intel_bios_driver_remove(struct drm_i915_private *dev_priv)
  */
 bool intel_bios_is_tv_present(struct drm_i915_private *dev_priv)
 {
+	const struct display_device_data *devdata;
 	const struct child_device_config *child;
-	int i;
 
 	if (!dev_priv->vbt.int_tv_support)
 		return false;
 
-	if (!dev_priv->vbt.child_dev_num)
+	if (list_empty(&dev_priv->vbt.display_devices))
 		return true;
 
-	for (i = 0; i < dev_priv->vbt.child_dev_num; i++) {
-		child = dev_priv->vbt.child_dev + i;
+	list_for_each_entry(devdata, &dev_priv->vbt.display_devices, node) {
+		child = &devdata->child;
+
 		/*
 		 * If the device type is not TV, continue.
 		 */
@@ -1963,14 +1963,14 @@  bool intel_bios_is_tv_present(struct drm_i915_private *dev_priv)
  */
 bool intel_bios_is_lvds_present(struct drm_i915_private *dev_priv, u8 *i2c_pin)
 {
+	const struct display_device_data *devdata;
 	const struct child_device_config *child;
-	int i;
 
-	if (!dev_priv->vbt.child_dev_num)
+	if (list_empty(&dev_priv->vbt.display_devices))
 		return true;
 
-	for (i = 0; i < dev_priv->vbt.child_dev_num; i++) {
-		child = dev_priv->vbt.child_dev + i;
+	list_for_each_entry(devdata, &dev_priv->vbt.display_devices, node) {
+		child = &devdata->child;
 
 		/* If the device type is not LFP, continue.
 		 * We have to check both the new identifiers as well as the
@@ -2012,6 +2012,7 @@  bool intel_bios_is_lvds_present(struct drm_i915_private *dev_priv, u8 *i2c_pin)
  */
 bool intel_bios_is_port_present(struct drm_i915_private *dev_priv, enum port port)
 {
+	const struct display_device_data *devdata;
 	const struct child_device_config *child;
 	static const struct {
 		u16 dp, hdmi;
@@ -2022,7 +2023,6 @@  bool intel_bios_is_port_present(struct drm_i915_private *dev_priv, enum port por
 		[PORT_E] = { DVO_PORT_DPE, DVO_PORT_HDMIE, },
 		[PORT_F] = { DVO_PORT_DPF, DVO_PORT_HDMIF, },
 	};
-	int i;
 
 	if (HAS_DDI(dev_priv)) {
 		const struct ddi_vbt_port_info *port_info =
@@ -2037,11 +2037,8 @@  bool intel_bios_is_port_present(struct drm_i915_private *dev_priv, enum port por
 	if (WARN_ON(port == PORT_A) || port >= ARRAY_SIZE(port_mapping))
 		return false;
 
-	if (!dev_priv->vbt.child_dev_num)
-		return false;
-
-	for (i = 0; i < dev_priv->vbt.child_dev_num; i++) {
-		child = dev_priv->vbt.child_dev + i;
+	list_for_each_entry(devdata, &dev_priv->vbt.display_devices, node) {
+		child = &devdata->child;
 
 		if ((child->dvo_port == port_mapping[port].dp ||
 		     child->dvo_port == port_mapping[port].hdmi) &&
@@ -2062,6 +2059,7 @@  bool intel_bios_is_port_present(struct drm_i915_private *dev_priv, enum port por
  */
 bool intel_bios_is_port_edp(struct drm_i915_private *dev_priv, enum port port)
 {
+	const struct display_device_data *devdata;
 	const struct child_device_config *child;
 	static const short port_mapping[] = {
 		[PORT_B] = DVO_PORT_DPB,
@@ -2070,16 +2068,12 @@  bool intel_bios_is_port_edp(struct drm_i915_private *dev_priv, enum port port)
 		[PORT_E] = DVO_PORT_DPE,
 		[PORT_F] = DVO_PORT_DPF,
 	};
-	int i;
 
 	if (HAS_DDI(dev_priv))
 		return dev_priv->vbt.ddi_port_info[port].supports_edp;
 
-	if (!dev_priv->vbt.child_dev_num)
-		return false;
-
-	for (i = 0; i < dev_priv->vbt.child_dev_num; i++) {
-		child = dev_priv->vbt.child_dev + i;
+	list_for_each_entry(devdata, &dev_priv->vbt.display_devices, node) {
+		child = &devdata->child;
 
 		if (child->dvo_port == port_mapping[port] &&
 		    (child->device_type & DEVICE_TYPE_eDP_BITS) ==
@@ -2128,13 +2122,10 @@  static bool child_dev_is_dp_dual_mode(const struct child_device_config *child,
 bool intel_bios_is_port_dp_dual_mode(struct drm_i915_private *dev_priv,
 				     enum port port)
 {
-	const struct child_device_config *child;
-	int i;
+	const struct display_device_data *devdata;
 
-	for (i = 0; i < dev_priv->vbt.child_dev_num; i++) {
-		child = dev_priv->vbt.child_dev + i;
-
-		if (child_dev_is_dp_dual_mode(child, port))
+	list_for_each_entry(devdata, &dev_priv->vbt.display_devices, node) {
+		if (child_dev_is_dp_dual_mode(&devdata->child, port))
 			return true;
 	}
 
@@ -2151,12 +2142,12 @@  bool intel_bios_is_port_dp_dual_mode(struct drm_i915_private *dev_priv,
 bool intel_bios_is_dsi_present(struct drm_i915_private *dev_priv,
 			       enum port *port)
 {
+	const struct display_device_data *devdata;
 	const struct child_device_config *child;
 	u8 dvo_port;
-	int i;
 
-	for (i = 0; i < dev_priv->vbt.child_dev_num; i++) {
-		child = dev_priv->vbt.child_dev + i;
+	list_for_each_entry(devdata, &dev_priv->vbt.display_devices, node) {
+		child = &devdata->child;
 
 		if (!(child->device_type & DEVICE_TYPE_MIPI_OUTPUT))
 			continue;
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 67bdfe6de3fa..2c0674a86dd8 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -720,8 +720,7 @@  struct intel_vbt_data {
 
 	int crt_ddc_pin;
 
-	int child_dev_num;
-	struct child_device_config *child_dev;
+	struct list_head display_devices;
 
 	struct ddi_vbt_port_info ddi_port_info[I915_MAX_PORTS];
 	struct sdvo_device_mapping sdvo_mappings[2];