Re: [PATCH v4 15/15] ipu3-cio2: Add cio2-bridge to ipu3-cio2 driver

[Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>]

Hi Dan,

On 03/01/2021 23:12, Daniel Scally wrote:
> Currently on platforms designed for Windows, connections between CIO2 and
> sensors are not properly defined in DSDT. This patch extends the ipu3-cio2
> driver to compensate by building software_node connections, parsing the
> connection properties from the sensor's SSDB buffer.
> 
> Suggested-by: Jordan Hand <jorhand@linux.microsoft.com>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> Signed-off-by: Daniel Scally <djrscally@gmail.com>
> ---
> Changes in v4:
> 
> 	- Added local definition of CIO2_MAX_LANES
> 	- Added some includes to cio2-bridge.h
> 	- Moved the inner loop of cio2_bridge_connect_sensors() to a
> 	  standalone function
> 	- Altered macros to make explicit assignments to members rather
> 	  than relying on position
> 	- A couple of minor format changes, mostly line wrapping
> 
>  MAINTAINERS                                   |   1 +
>  drivers/media/pci/intel/ipu3/Kconfig          |  18 ++
>  drivers/media/pci/intel/ipu3/Makefile         |   1 +
>  drivers/media/pci/intel/ipu3/cio2-bridge.c    | 302 ++++++++++++++++++
>  drivers/media/pci/intel/ipu3/cio2-bridge.h    | 125 ++++++++
>  drivers/media/pci/intel/ipu3/ipu3-cio2-main.c |  33 ++
>  drivers/media/pci/intel/ipu3/ipu3-cio2.h      |   6 +
>  7 files changed, 486 insertions(+)
>  create mode 100644 drivers/media/pci/intel/ipu3/cio2-bridge.c
>  create mode 100644 drivers/media/pci/intel/ipu3/cio2-bridge.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 16b544624577..e7784b4bc8ea 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -8943,6 +8943,7 @@ INTEL IPU3 CSI-2 CIO2 DRIVER
>  M:	Yong Zhi <yong.zhi@intel.com>
>  M:	Sakari Ailus <sakari.ailus@linux.intel.com>
>  M:	Bingbu Cao <bingbu.cao@intel.com>
> +M:	Dan Scally <djrscally@gmail.com>
>  R:	Tianshu Qiu <tian.shu.qiu@intel.com>
>  L:	linux-media@vger.kernel.org
>  S:	Maintained
> diff --git a/drivers/media/pci/intel/ipu3/Kconfig b/drivers/media/pci/intel/ipu3/Kconfig
> index 82d7f17e6a02..96a2231b16ad 100644
> --- a/drivers/media/pci/intel/ipu3/Kconfig
> +++ b/drivers/media/pci/intel/ipu3/Kconfig
> @@ -16,3 +16,21 @@ config VIDEO_IPU3_CIO2
>  	  Say Y or M here if you have a Skylake/Kaby Lake SoC with MIPI CSI-2
>  	  connected camera.
>  	  The module will be called ipu3-cio2.
> +
> +config CIO2_BRIDGE
> +	bool "IPU3 CIO2 Sensors Bridge"
> +	depends on VIDEO_IPU3_CIO2
> +	help
> +	  This extension provides an API for the ipu3-cio2 driver to create
> +	  connections to cameras that are hidden in the SSDB buffer in ACPI.
> +	  It can be used to enable support for cameras in detachable / hybrid
> +	  devices that ship with Windows.
> +
> +	  Say Y here if your device is a detachable / hybrid laptop that comes
> +	  with Windows installed by the OEM, for example:
> +
> +		- Microsoft Surface models (except Surface Pro 3)
> +		- The Lenovo Miix line (for example the 510, 520, 710 and 720)
> +		- Dell 7285
> +
> +	  If in doubt, say N here.
> diff --git a/drivers/media/pci/intel/ipu3/Makefile b/drivers/media/pci/intel/ipu3/Makefile
> index 429d516452e4..933777e6ea8a 100644
> --- a/drivers/media/pci/intel/ipu3/Makefile
> +++ b/drivers/media/pci/intel/ipu3/Makefile
> @@ -2,3 +2,4 @@
>  obj-$(CONFIG_VIDEO_IPU3_CIO2) += ipu3-cio2.o
>  
>  ipu3-cio2-y += ipu3-cio2-main.o
> +ipu3-cio2-$(CONFIG_CIO2_BRIDGE) += cio2-bridge.o
> diff --git a/drivers/media/pci/intel/ipu3/cio2-bridge.c b/drivers/media/pci/intel/ipu3/cio2-bridge.c
> new file mode 100644
> index 000000000000..3a7bedb08f66
> --- /dev/null
> +++ b/drivers/media/pci/intel/ipu3/cio2-bridge.c
> @@ -0,0 +1,302 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Author: Dan Scally <djrscally@gmail.com> */
> +
> +#include <linux/acpi.h>
> +#include <linux/device.h>
> +#include <linux/pci.h>
> +#include <linux/property.h>
> +#include <media/v4l2-fwnode.h>
> +
> +#include "cio2-bridge.h"
> +
> +/*
> + * Extend this array with ACPI Hardware IDs of devices known to be working
> + * plus the number of link-frequencies expected by their drivers, along with
> + * the frequency values in hertz. This is somewhat opportunistic way of adding
> + * support for this for now in the hopes of a better source for the information
> + * (possibly some encoded value in the SSDB buffer that we're unaware of)
> + * becoming apparent in the future.
> + *
> + * Do not add an entry for a sensor that is not actually supported.
> + */
> +static const struct cio2_sensor_config cio2_supported_sensors[] = {
> +	CIO2_SENSOR_CONFIG("INT33BE", 0),
> +	CIO2_SENSOR_CONFIG("OVTI2680", 0),

I don't know if these are expressed anywhere else but would it be
helpful to add a comment, or indicator as to what the actual sensor is
that is represented by this HID?

I can make an assumption about what an OVTI2680 might be, but the
INT33BE is quite opaque. It's not clear what support that adds.

Unless no one cares what the sensor is that is, but I would anticipate
anyone looking here to add a new sensor might want to investigate what
was already in the table?



> +};
> +
> +static const struct cio2_property_names prop_names = {
> +	.clock_frequency = "clock-frequency",
> +	.rotation = "rotation",
> +	.bus_type = "bus-type",
> +	.data_lanes = "data-lanes",
> +	.remote_endpoint = "remote-endpoint",
> +	.link_frequencies = "link-frequencies",
> +};
> +
> +static int cio2_bridge_read_acpi_buffer(struct acpi_device *adev, char *id,
> +					void *data, u32 size)
> +{
> +	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> +	union acpi_object *obj;
> +	acpi_status status;
> +	int ret = 0;
> +
> +	status = acpi_evaluate_object(adev->handle, id, NULL, &buffer);
> +	if (ACPI_FAILURE(status))
> +		return -ENODEV;
> +
> +	obj = buffer.pointer;
> +	if (!obj) {
> +		dev_err(&adev->dev, "Couldn't locate ACPI buffer\n");
> +		return -ENODEV;
> +	}
> +
> +	if (obj->type != ACPI_TYPE_BUFFER) {
> +		dev_err(&adev->dev, "Not an ACPI buffer\n");
> +		ret = -ENODEV;
> +		goto out_free_buff;
> +	}
> +
> +	if (obj->buffer.length > size) {
> +		dev_err(&adev->dev, "Given buffer is too small\n");
> +		ret = -EINVAL;
> +		goto out_free_buff;
> +	}
> +
> +	memcpy(data, obj->buffer.pointer, obj->buffer.length);
> +
> +out_free_buff:
> +	kfree(buffer.pointer);
> +	return ret;
> +}
> +
> +static void cio2_bridge_create_fwnode_properties(
> +	struct cio2_sensor *sensor,
> +	const struct cio2_sensor_config *cfg)
> +{
> +	unsigned int i;
> +
> +	sensor->prop_names = prop_names;
> +
> +	for (i = 0; i < CIO2_MAX_LANES; i++)
> +		sensor->data_lanes[i] = i + 1;

Does something support lane swapping somewhere?
I assume this is just mapping each lane directly through.

Otherwise, I'm quite looking forwards to all of this ;-)

Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

> +
> +	sensor->local_ref[0].node = &sensor->swnodes[SWNODE_CIO2_ENDPOINT];
> +	sensor->remote_ref[0].node = &sensor->swnodes[SWNODE_SENSOR_ENDPOINT];
> +
> +	sensor->dev_properties[0] = PROPERTY_ENTRY_U32(
> +					sensor->prop_names.clock_frequency,
> +					sensor->ssdb.mclkspeed);
> +	sensor->dev_properties[1] = PROPERTY_ENTRY_U8(
> +					sensor->prop_names.rotation,
> +					sensor->ssdb.degree);
> +
> +	sensor->ep_properties[0] = PROPERTY_ENTRY_U32(
> +					sensor->prop_names.bus_type,
> +					V4L2_FWNODE_BUS_TYPE_CSI2_DPHY);
> +	sensor->ep_properties[1] = PROPERTY_ENTRY_U32_ARRAY_LEN(
> +					sensor->prop_names.data_lanes,
> +					sensor->data_lanes,
> +					sensor->ssdb.lanes);
> +	sensor->ep_properties[2] = PROPERTY_ENTRY_REF_ARRAY(
> +					sensor->prop_names.remote_endpoint,
> +					sensor->local_ref);
> +
> +	if (cfg->nr_link_freqs > 0)
> +		sensor->ep_properties[3] = PROPERTY_ENTRY_U64_ARRAY_LEN(
> +						sensor->prop_names.link_frequencies,
> +						cfg->link_freqs,
> +						cfg->nr_link_freqs);
> +
> +	sensor->cio2_properties[0] = PROPERTY_ENTRY_U32_ARRAY_LEN(
> +					sensor->prop_names.data_lanes,
> +					sensor->data_lanes,
> +					sensor->ssdb.lanes);
> +	sensor->cio2_properties[1] = PROPERTY_ENTRY_REF_ARRAY(
> +					sensor->prop_names.remote_endpoint,
> +					sensor->remote_ref);
> +}
> +
> +static void cio2_bridge_init_swnode_names(struct cio2_sensor *sensor)
> +{
> +	snprintf(sensor->node_names.remote_port,
> +		 sizeof(sensor->node_names.remote_port),
> +		 SWNODE_GRAPH_PORT_NAME_FMT, sensor->ssdb.link);
> +	snprintf(sensor->node_names.port,
> +		 sizeof(sensor->node_names.port),
> +		 SWNODE_GRAPH_PORT_NAME_FMT, 0); /* Always port 0 */
> +	snprintf(sensor->node_names.endpoint,
> +		 sizeof(sensor->node_names.endpoint),
> +		 SWNODE_GRAPH_ENDPOINT_NAME_FMT, 0); /* And endpoint 0 */
> +}
> +
> +static void cio2_bridge_create_connection_swnodes(struct cio2_bridge *bridge,
> +						  struct cio2_sensor *sensor)
> +{
> +	struct software_node *nodes = sensor->swnodes;
> +
> +	cio2_bridge_init_swnode_names(sensor);
> +
> +	nodes[SWNODE_SENSOR_HID] = NODE_SENSOR(sensor->name,
> +					       sensor->dev_properties);
> +	nodes[SWNODE_SENSOR_PORT] = NODE_PORT(sensor->node_names.port,
> +					      &nodes[SWNODE_SENSOR_HID]);
> +	nodes[SWNODE_SENSOR_ENDPOINT] = NODE_ENDPOINT(
> +						sensor->node_names.endpoint,
> +						&nodes[SWNODE_SENSOR_PORT],
> +						sensor->ep_properties);
> +	nodes[SWNODE_CIO2_PORT] = NODE_PORT(sensor->node_names.remote_port,
> +					    &bridge->cio2_hid_node);
> +	nodes[SWNODE_CIO2_ENDPOINT] = NODE_ENDPOINT(
> +						sensor->node_names.endpoint,
> +						&nodes[SWNODE_CIO2_PORT],
> +						sensor->cio2_properties);
> +}
> +
> +static void cio2_bridge_unregister_sensors(struct cio2_bridge *bridge)
> +{
> +	struct cio2_sensor *sensor;
> +	unsigned int i;
> +
> +	for (i = 0; i < bridge->n_sensors; i++) {
> +		sensor = &bridge->sensors[i];
> +		software_node_unregister_nodes(sensor->swnodes);
> +		acpi_dev_put(sensor->adev);
> +	}
> +}
> +
> +static int cio2_bridge_connect_sensor(const struct cio2_sensor_config *cfg,
> +				      struct cio2_bridge *bridge,
> +				      struct pci_dev *cio2)
> +{
> +	struct fwnode_handle *fwnode;
> +	struct cio2_sensor *sensor;
> +	struct acpi_device *adev;
> +	int ret;
> +
> +	for_each_acpi_dev_match(adev, cfg->hid, NULL, -1) {
> +		if (bridge->n_sensors >= CIO2_NUM_PORTS) {
> +			dev_err(&cio2->dev, "Exceeded available CIO2 ports\n");
> +			cio2_bridge_unregister_sensors(bridge);
> +			ret = -EINVAL;
> +			goto err_out;
> +		}
> +
> +		if (!adev->status.enabled)
> +			continue;
> +
> +		sensor = &bridge->sensors[bridge->n_sensors];
> +		sensor->adev = adev;
> +		strscpy(sensor->name, cfg->hid, sizeof(sensor->name));
> +
> +		ret = cio2_bridge_read_acpi_buffer(adev, "SSDB",
> +						   &sensor->ssdb,
> +						   sizeof(sensor->ssdb));
> +		if (ret)
> +			goto err_put_adev;
> +
> +		if (sensor->ssdb.lanes > CIO2_MAX_LANES) {
> +			dev_err(&adev->dev,
> +				"Number of lanes in SSDB is invalid\n");
> +			ret = -EINVAL;
> +			goto err_put_adev;
> +		}
> +
> +		cio2_bridge_create_fwnode_properties(sensor, cfg);
> +		cio2_bridge_create_connection_swnodes(bridge, sensor);
> +
> +		ret = software_node_register_nodes(sensor->swnodes);
> +		if (ret)
> +			goto err_put_adev;
> +
> +		fwnode = software_node_fwnode(&sensor->swnodes[SWNODE_SENSOR_HID]);
> +		if (!fwnode) {
> +			ret = -ENODEV;
> +			goto err_free_swnodes;
> +		}
> +
> +		adev->fwnode.secondary = fwnode;
> +
> +		dev_info(&cio2->dev, "Found supported sensor %s\n",
> +			 acpi_dev_name(adev));
> +
> +		bridge->n_sensors++;
> +	}
> +
> +	return 0;
> +
> +err_free_swnodes:
> +	software_node_unregister_nodes(sensor->swnodes);
> +err_put_adev:
> +	acpi_dev_put(sensor->adev);
> +err_out:
> +	return ret;
> +}
> +
> +static int cio2_bridge_connect_sensors(struct cio2_bridge *bridge,
> +				       struct pci_dev *cio2)
> +{
> +	unsigned int i;
> +	int ret;
> +
> +	for (i = 0; i < ARRAY_SIZE(cio2_supported_sensors); i++) {
> +		const struct cio2_sensor_config *cfg = &cio2_supported_sensors[i];
> +
> +		ret = cio2_bridge_connect_sensor(cfg, bridge, cio2);
> +		if (ret)
> +			goto err_unregister_sensors;
> +	}
> +
> +	return 0;
> +
> +err_unregister_sensors:
> +	cio2_bridge_unregister_sensors(bridge);
> +	return ret;
> +}
> +
> +int cio2_bridge_init(struct pci_dev *cio2)
> +{
> +	struct device *dev = &cio2->dev;
> +	struct fwnode_handle *fwnode;
> +	struct cio2_bridge *bridge;
> +	int ret;
> +
> +	bridge = kzalloc(sizeof(*bridge), GFP_KERNEL);
> +	if (!bridge)
> +		return -ENOMEM;
> +
> +	strscpy(bridge->cio2_node_name, CIO2_HID, sizeof(bridge->cio2_node_name));
> +	bridge->cio2_hid_node.name = bridge->cio2_node_name;
> +
> +	ret = software_node_register(&bridge->cio2_hid_node);
> +	if (ret < 0) {
> +		dev_err(dev, "Failed to register the CIO2 HID node\n");
> +		goto err_free_bridge;
> +	}
> +
> +	ret = cio2_bridge_connect_sensors(bridge, cio2);
> +	if (ret || bridge->n_sensors == 0)
> +		goto err_unregister_cio2;
> +
> +	dev_info(dev, "Connected %d cameras\n", bridge->n_sensors);
> +
> +	fwnode = software_node_fwnode(&bridge->cio2_hid_node);
> +	if (!fwnode) {
> +		dev_err(dev, "Error getting fwnode from cio2 software_node\n");
> +		ret = -ENODEV;
> +		goto err_unregister_sensors;
> +	}
> +
> +	set_secondary_fwnode(dev, fwnode);
> +
> +	return 0;
> +
> +err_unregister_sensors:
> +	cio2_bridge_unregister_sensors(bridge);
> +err_unregister_cio2:
> +	software_node_unregister(&bridge->cio2_hid_node);
> +err_free_bridge:
> +	kfree(bridge);
> +
> +	return ret;
> +}
> diff --git a/drivers/media/pci/intel/ipu3/cio2-bridge.h b/drivers/media/pci/intel/ipu3/cio2-bridge.h
> new file mode 100644
> index 000000000000..3ec4ed44aced
> --- /dev/null
> +++ b/drivers/media/pci/intel/ipu3/cio2-bridge.h
> @@ -0,0 +1,125 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* Author: Dan Scally <djrscally@gmail.com> */
> +#ifndef __CIO2_BRIDGE_H
> +#define __CIO2_BRIDGE_H
> +
> +#include <linux/property.h>
> +#include <linux/types.h>
> +
> +#include "ipu3-cio2.h"
> +
> +#define CIO2_HID				"INT343E"
> +#define CIO2_MAX_LANES				4
> +#define MAX_NUM_LINK_FREQS			3
> +
> +#define CIO2_SENSOR_CONFIG(_HID, _NR, ...)	\
> +	{					\
> +		.hid = _HID,			\
> +		.nr_link_freqs = _NR,		\
> +		.link_freqs = { __VA_ARGS__ }	\
> +	}
> +
> +#define NODE_SENSOR(_HID, _PROPS)		\
> +	((const struct software_node) {		\
> +		.name = _HID,			\
> +		.properties = _PROPS,		\
> +	})
> +
> +#define NODE_PORT(_PORT, _SENSOR_NODE)		\
> +	((const struct software_node) {		\
> +		.name = _PORT,			\
> +		.parent = _SENSOR_NODE,		\
> +	})
> +
> +#define NODE_ENDPOINT(_EP, _PORT, _PROPS)	\
> +	((const struct software_node) {		\
> +		.name = _EP,			\
> +		.parent = _PORT,		\
> +		.properties = _PROPS,		\
> +	})
> +
> +enum cio2_sensor_swnodes {
> +	SWNODE_SENSOR_HID,
> +	SWNODE_SENSOR_PORT,
> +	SWNODE_SENSOR_ENDPOINT,
> +	SWNODE_CIO2_PORT,
> +	SWNODE_CIO2_ENDPOINT,
> +	SWNODE_COUNT
> +};
> +
> +/* Data representation as it is in ACPI SSDB buffer */
> +struct cio2_sensor_ssdb {
> +	u8 version;
> +	u8 sku;
> +	u8 guid_csi2[16];
> +	u8 devfunction;
> +	u8 bus;
> +	u32 dphylinkenfuses;
> +	u32 clockdiv;
> +	u8 link;
> +	u8 lanes;
> +	u32 csiparams[10];
> +	u32 maxlanespeed;
> +	u8 sensorcalibfileidx;
> +	u8 sensorcalibfileidxInMBZ[3];
> +	u8 romtype;
> +	u8 vcmtype;
> +	u8 platforminfo;
> +	u8 platformsubinfo;
> +	u8 flash;
> +	u8 privacyled;
> +	u8 degree;
> +	u8 mipilinkdefined;
> +	u32 mclkspeed;
> +	u8 controllogicid;
> +	u8 reserved1[3];
> +	u8 mclkport;
> +	u8 reserved2[13];
> +} __packed;
> +
> +struct cio2_property_names {
> +	char clock_frequency[16];
> +	char rotation[9];
> +	char bus_type[9];
> +	char data_lanes[11];
> +	char remote_endpoint[16];
> +	char link_frequencies[17];
> +};
> +
> +struct cio2_node_names {
> +	char port[7];
> +	char endpoint[11];
> +	char remote_port[7];
> +};
> +
> +struct cio2_sensor_config {
> +	const char *hid;
> +	const u8 nr_link_freqs;
> +	const u64 link_freqs[MAX_NUM_LINK_FREQS];
> +};
> +
> +struct cio2_sensor {
> +	char name[ACPI_ID_LEN];
> +	struct acpi_device *adev;
> +
> +	struct software_node swnodes[6];
> +	struct cio2_node_names node_names;
> +
> +	u32 data_lanes[4];
> +	struct cio2_sensor_ssdb ssdb;
> +	struct cio2_property_names prop_names;
> +	struct property_entry ep_properties[5];
> +	struct property_entry dev_properties[3];
> +	struct property_entry cio2_properties[3];
> +	struct software_node_ref_args local_ref[1];
> +	struct software_node_ref_args remote_ref[1];
> +};
> +
> +struct cio2_bridge {
> +	char cio2_node_name[ACPI_ID_LEN];
> +	struct software_node cio2_hid_node;
> +	unsigned int n_sensors;
> +	struct cio2_sensor sensors[CIO2_NUM_PORTS];
> +};
> +
> +#endif
> diff --git a/drivers/media/pci/intel/ipu3/ipu3-cio2-main.c b/drivers/media/pci/intel/ipu3/ipu3-cio2-main.c
> index 36e354ecf71e..50c7ea467795 100644
> --- a/drivers/media/pci/intel/ipu3/ipu3-cio2-main.c
> +++ b/drivers/media/pci/intel/ipu3/ipu3-cio2-main.c
> @@ -1702,11 +1702,28 @@ static void cio2_queues_exit(struct cio2_device *cio2)
>  		cio2_queue_exit(cio2, &cio2->queue[i]);
>  }
>  
> +static bool cio2_check_fwnode_graph(struct fwnode_handle *fwnode)
> +{
> +	struct fwnode_handle *endpoint;
> +
> +	if (IS_ERR_OR_NULL(fwnode))
> +		return false;
> +
> +	endpoint = fwnode_graph_get_next_endpoint(fwnode, NULL);
> +	if (endpoint) {
> +		fwnode_handle_put(endpoint);
> +		return true;
> +	}
> +
> +	return cio2_check_fwnode_graph(fwnode->secondary);
> +}
> +
>  /**************** PCI interface ****************/
>  
>  static int cio2_pci_probe(struct pci_dev *pci_dev,
>  			  const struct pci_device_id *id)
>  {
> +	struct fwnode_handle *fwnode = dev_fwnode(&pci_dev->dev);
>  	struct cio2_device *cio2;
>  	int r;
>  
> @@ -1715,6 +1732,22 @@ static int cio2_pci_probe(struct pci_dev *pci_dev,
>  		return -ENOMEM;
>  	cio2->pci_dev = pci_dev;
>  
> +	/*
> +	 * On some platforms no connections to sensors are defined in firmware,
> +	 * if the device has no endpoints then we can try to build those as
> +	 * software_nodes parsed from SSDB.
> +	 */
> +	if (!cio2_check_fwnode_graph(fwnode)) {
> +		if (fwnode && !IS_ERR_OR_NULL(fwnode->secondary)) {
> +			dev_err(&pci_dev->dev, "fwnode graph has no endpoints connected\n");
> +			return -EINVAL;
> +		}
> +
> +		r = cio2_bridge_init(pci_dev);
> +		if (r)
> +			return r;
> +	}
> +
>  	r = pcim_enable_device(pci_dev);
>  	if (r) {
>  		dev_err(&pci_dev->dev, "failed to enable device (%d)\n", r);
> diff --git a/drivers/media/pci/intel/ipu3/ipu3-cio2.h b/drivers/media/pci/intel/ipu3/ipu3-cio2.h
> index 62187ab5ae43..dc3e343a37fb 100644
> --- a/drivers/media/pci/intel/ipu3/ipu3-cio2.h
> +++ b/drivers/media/pci/intel/ipu3/ipu3-cio2.h
> @@ -455,4 +455,10 @@ static inline struct cio2_queue *vb2q_to_cio2_queue(struct vb2_queue *vq)
>  	return container_of(vq, struct cio2_queue, vbq);
>  }
>  
> +#if IS_ENABLED(CONFIG_CIO2_BRIDGE)
> +int cio2_bridge_init(struct pci_dev *cio2);
> +#else
> +int cio2_bridge_init(struct pci_dev *cio2) { return 0; }
> +#endif
> +
>  #endif
>