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NS:sercx._SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG

_SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG (sercx.h)

The SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG structure contains information that version 2 of the serial framework extension (SerCx2) uses to configure a new system-DMA-transmit object.

serports\sercx2_system_dma_transmit_config.htm

serports

04/23/2018

SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG structure

*PSERCX2_SYSTEM_DMA_TRANSMIT_CONFIG, 2/PSERCX2_SYSTEM_DMA_TRANSMIT_CONFIG, 2/SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG, PSERCX2_SYSTEM_DMA_TRANSMIT_CONFIG, PSERCX2_SYSTEM_DMA_TRANSMIT_CONFIG structure pointer [Serial Ports], SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG, SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG structure [Serial Ports], _SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG, serports.sercx2_system_dma_transmit_config

sercx.h

Windows

Supported starting with Windows 8.1.

Windows

SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG, *PSERCX2_SYSTEM_DMA_TRANSMIT_CONFIG

_SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG

sercx/_SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG

PSERCX2_SYSTEM_DMA_TRANSMIT_CONFIG

sercx/PSERCX2_SYSTEM_DMA_TRANSMIT_CONFIG

SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG

sercx/SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG

APIRef

kbSyntax

HeaderDef

2.0\Sercx.h

_SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG

PSERCX2_SYSTEM_DMA_TRANSMIT_CONFIG

SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG

_SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG structure

-description

The SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG structure contains information that version 2 of the serial framework extension (SerCx2) uses to configure a new system-DMA-transmit object.

-struct-fields

-field Size

The size, in bytes, of this structure. The SerCx2SystemDmaTransmitCreate method uses this member to determine which version of the structure the caller is using. The size of this structure might change in future versions of the Sercx.h header file.

-field MaximumTransferLength

The default maximum size, in bytes, that the serial controller can handle in a single system DMA transfer. If the size of the buffer in the write (IRP_MJ_WRITE) request is larger than this maximum size, SerCx2 uses multiple DMA transfers to handle the request, and limits each transfer to the maximum length.

-field MinimumTransactionLength

The minimum length, in bytes, of a system-DMA-transmit transaction. If the length of the buffer in a write request is less than this minimum length, SerCx2 uses programmed I/O (PIO) for the transaction.

-field DmaAlignment

DMA alignment requirement. Specifies how the starting address of a transfer in a system-DMA-transmit transaction must be aligned in memory. Set this member to the appropriate FILE_XXX_ALIGNMENT constant in the Wdm.h header file. For example, FILE_WORD_ALIGNMENT indicates that the starting DMA address must be aligned to a two-byte boundary in memory, FILE_LONG_ALIGNMENT indicates that the address must be aligned to a four-byte boundary, and so on. SerCx2 does not support FILE_BYTE_ALIGNMENT. The minimum transfer unit (MTU) of the system DMA adapter should be greater than or equal to the required alignment. For example, if the MTU is four bytes, DmaAlignment must be at least FILE_LONG_ALIGNMENT.

-field MaximumScatterGatherFragments

The maximum number of buffer fragments that can be specified in the scatter/gather list for a DMA transfer in a system-DMA-transmit transaction.

-field DmaWidth

The width of the data register at the address specified by DeviceAddress. Possible values are Width8Bits, Width16Bits, Width32Bits, and Width64Bits.

-field DeviceAddress

The translated device address to which the DMA controller transfers data to be transmitted. For more information, see the description of the DeviceAddress member in WDF_DMA_SYSTEM_PROFILE_CONFIG.

-field DmaDescriptor

A pointer to the CM_PARTIAL_RESOURCE_DESCRIPTOR structure that describes the system DMA resource to use for transmit transactions. The serial controller driver gets this structure from the raw resource list it receives in the EvtDevicePrepareHardware callback that starts the serial controller.

-field MinimumTransferUnitOverride

An override value to use in place of the default minimum transfer unit. The number of bytes specified by an element in a scatter/gather list must be an integer multiple of the minimum transfer unit. A value of zero indicates that the default minimum transfer unit should be used. For more information about the default minimum transfer unit, see DMA_ADAPTER_INFO_V1.

-field Exclusive

Whether to use system-DMA-transmit transactions exclusively to handle write (IRP_MJ_WRITE) requests. Set to TRUE to indicate that write requests should use system-DMA-transmit transactions exclusively. Set to FALSE to indicate that write requests can use a combination of system-DMA-transmit transactions and PIO-transmit transactions.

Set this member to TRUE only if the minimum transfer unit for system-DMA-transmit transactions is one byte, the minimum transaction length is one byte, and the write buffer for the transaction can start on any byte boundary in memory.

If Exclusive is TRUE, the MinimumTransferUnitOverride, Alignment, and MinimumTransactionLength members must be zero.

-field EvtSerCx2SystemDmaTransmitInitializeTransaction

A pointer to the driver-implemented EvtSerCx2SystemDmaTransmitInitializeTransaction event callback function. This member is optional and can be set to NULL to indicate that the driver does not implement the function.

-field EvtSerCx2SystemDmaTransmitCleanupTransaction

A pointer to the driver-implemented EvtSerCx2SystemDmaTransmitCleanupTransaction event callback function. This member is optional and can be set to NULL to indicate that the driver does not implement the function.

-field EvtSerCx2SystemDmaTransmitConfigureDmaChannel

A pointer to the driver-implemented EvtSerCx2SystemDmaTransmitConfigureDmaChannel event callback function. This member is optional and can be set to NULL to indicate that the driver does not implement the function.

-field EvtSerCx2SystemDmaTransmitDrainFifo

A pointer to the driver-implemented EvtSerCx2SystemDmaTransmitDrainFifo event callback function. This member is optional and can be set to NULL to indicate that the driver does not implement the function. However, a driver that implements this function must also implement EvtSerCx2SystemDmaTransmitCancelDrainFifo and EvtSerCx2SystemDmaTransmitPurgeFifo functions.

-field EvtSerCx2SystemDmaTransmitCancelDrainFifo

A pointer to the driver-implemented EvtSerCx2SystemDmaTransmitCancelDrainFifo event callback function. This member is optional and can be set to NULL to indicate that the driver does not implement the function. However, a driver that implements this function must also implement EvtSerCx2SystemDmaTransmitDrainFifo and EvtSerCx2SystemDmaTransmitPurgeFifo functions.

-field EvtSerCx2SystemDmaTransmitPurgeFifo

A pointer to the driver-implemented EvtSerCx2SystemDmaTransmitPurgeFifo event callback function. This member is optional and can be set to NULL to indicate that the driver does not implement the function. However, a driver that implements this function must also implement EvtSerCx2SystemDmaTransmitDrainFifo and EvtSerCx2SystemDmaTransmitCancelDrainFifo functions.

-remarks

The SerCx2SystemDmaTransmitCreate method accepts a pointer to a SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG structure as an input parameter. Before calling SerCx2SystemDmaTransmitCreate, call the SERCX2_SYSTEM_DMA_TRANSMIT_CONFIG_INIT function to initialize this structure.