Updates for IddCx versions 1.11 and later

This article describes the changes being made in IddCx 1.11. A single indirect display driver (IDD) binary built against IddCx 1.11 can run on Windows 10 1803 and above using runtime checks to verify if DDI changes in IddCx 1.11 are available on that system. For more information, see Building a WDF driver for multiple versions of Windows.

The IddCx 1.11 changes fall into the following categories:

• Update the IddCxGetVersion version (console and remote). For a complete list of IddCx-related version information, see IddCx versions.
• Add ability to query OS feature support.
• Add support for using the D3D12 API.
• Add a new atomic read/write I2C DDI.
• Add support for DisplayID only descriptors.
• Add support for updating the static desktop reencode count.

Update IddCxGetVersion version

The value returned by IddCxGetVersion has been updated to return 0x1B00.

Query OS feature support

Drivers now have the ability to determine if a particular feature of IddCx 1.11 is available in the underlying OS by calling IddCxCheckOsFeatureSupport. Multiple OS versions can report support for IddCx 1.11 through IddCxGetVersion, but possibly only some of the features will be available.

D3D12 support

IddCx 1.11 drivers that support D3D12 can associate an ID3D12Device object with a swapchain and receive ID3D12Resource objects using calls to IddCxSwapChainReleaseAndAcquireBuffer2. An overview of the related changes is given in the following sections.

Associating a D3D12 device with a swapchain

If a driver wishes to receive D3D12 frames then an ID3D12Device object needs to be provided in a call to IddCxSwapChainSetDevice2.

Receiving D3D12 frames

After a driver has called IddCxSwapChainSetDevice2 and provided an ID3D12Device object, the IDARG_OUT_RELEASEANDACQUIREBUFFER2 passed to calls to IddCxSwapChainReleaseAndAcquireBuffer2 will have the IDDCX_METADATA2_VALID_FLAGS_D3D12SURFACE flag set and then the driver should use IDARG_OUT_RELEASEANDACQUIREBUFFER2.MetaData.pD3d12Surface to access the pixel data.

Synchronizing access to D3D12 surfaces

A significant change when a driver uses D3D12 is the synchronization model that controls access to the swap chain surfaces and avoid issues such as lock ups and accessing out of date pixel data has changed. Due to the more fine grained control D3D12 uses, drivers need to explicitly tell the OS which command queue is going to use the surface as input data.

More details on the driver responsibilities with regards to synchronization are given in the IDDCX_METADATA2 additions remarks.

Atomic I2C support

A 1.11 driver that supports I2C by providing the EVT_IDD_CX_MONITOR_I2C_RECEIVE and EVT_IDD_CX_MONITOR_I2C_TRANSMIT DDIs must also provide EVT_IDD_CX_MONITOR_I2C_TRANSMIT_AND_RECEIVE. This new DDI performs an I2C operation in a single call to help drivers that perform their own I2C operations from not interleaving with OS calls.

DisplayID only descriptor support

A new descriptor type, IDDCX_MONITOR_DESCRIPTION_TYPE_DISPLAYID, has been added to the IDDCX_MONITOR_DESCRIPTION_TYPE enumeration used in the arguments passed to IddCxMonitorCreate and IddCxMonitorCreate2. This should be used when the provided descriptor contains just a DisplayID descriptor and no EDID blocks at all.

Updating static desktop reencode count

Currently the static desktop reencode count is specified when creating an adapter. A new DDI now allows this value to be updated on a swap chain after the adapter is created.

Supporting a 1.11 driver running down level

If a 1.11 driver is to run on older Windows releases, there are steps you need to take to ensure compatibility.

• The driver must set the size of the IDD_CX_CLIENT_CONFIG structure using the IDD_CX_CLIENT_CONFIG_INIT macro.
• The driver must not set any of the new flags added to IDDCX_ADAPTER_FLAGS.
• The driver must not try and call any new functions provided by the OS as they aren't available. IDD_IS_FUNCTION_AVAILABLE can be used to check.
• None of the new functions can be exported. Drivers can use the IDD_IS_FIELD_AVAILABLE macro to check if the EvtIddXxx callback should be written to the IDD_CX_CLIENT_CONFIG structure.
• Even if the OS returns 0x1B00 from a call to IddCxGetVersion, the driver must query for specific feature support by calling IddCxCheckOsFeatureSupport.

The following example shows how IDD_IS_FIELD_AVAILABLE can be used:

if (IDD_IS_FIELD_AVAILABLE(IDD_CX_CLIENT_CONFIG, EvtIddCxMonitorI2CTransmitAndReceive))
{
    IddCxClientConfig.EvtIddCxMonitorI2CTransmitAndReceive = MonitorI2CTransmitAndReceive;
}

For more information, see Building IddCx 1.4 drivers.

Which functions are used

Previous releases

For information about changes in earlier IddCx versions, see the following articles:

• Updates for IddCx versions 1.10 and later
• Updates for IddCx versions 1.9 and later
• Updates for IddCx versions 1.8 and later
• Updates for IddCx versions 1.7 and later
• Updates for IddCx versions 1.6 and later
• Updates for IddCx versions 1.4 and later