d_map_query Kernel Service

Purpose

Queries the amount of direct memory access (DMA) space or DMA windows available on the partition end point. To use full 64-bit DMA all device drivers must call the d_map_query kernel service before attempting to initialize a new DMA window or before attempting to allocate DMA space within an existing DMA window by using the d_map_init_ext kernel service. Device drivers that do not use full 64-bit DMA should not call this service.

Syntax

#include <sys/types.h>
#include <sys/dma.h>
#include <sys/kerrno.h>

kerrno_t d_map_query(bid, slot, flags, cmd, dq_info)
uint64_t  bid;
uint64_t  slot;
uint64_t  flags;
uint64_t  cmd;
void *    dq_info;

Parameter

Description

The d_map_query kernel service allows the device driver to determine the amount of DMA space available within the DMA window or the amount of DMA windows available for a particular partition end point.

The d_map_query kernel service Dynamic DMA Windows Query (DDW_QUERY) option is supported only on partition end points that support the dynamic DMA windows (DDW_QUERY) option. The d_map_query kernel service can also be used to determine the dynamic DMA windows capability of a particular partition endpoint. When a slot is initialized on a reboot or power-on operation of the partition or on a DR isolate operation that encompasses the partition endpoint, a default DMA window is always allocated for less than 4 GB. After the first call to the d_map_query kernel service with the DDW_QUERY option, the default DMA window is removed. This leaves no usable DMA window on the partition endpoint until the d_map_init_ext kernel service is called to initialize a new DMA window.

The caller of the d_map_query kernel service must pass the desired command to the cmd parameter and have the appropriate dq_info parameter initialized.

The options available for the cmd parameter are defined in the <sys/dma.h> header file, and are described as follows:

DDW_QUERY

Returns the number of additional DMA windows available for a partition endpoint. The dq_ddw_resources_t structure must be passed to the dq_info parameter for this command. The dqdr_version field in the structure should be assigned as DQDR_VERSION.

DMA_QUERY

Returns the maximum amount of contiguous pages available for a given page size in all existing DMA windows. The dq_dma_available_t structure must be passed to the dq_info parameter for this command. The dqda_version field in the structure should be assigned as DQDA_VERSION and the corresponding I/O page size for the query must be specified. The supported I/O page size for the DMA operation can be obtained from the d_map_query kernel service by running the DDW_QUERY command.

The dq_ddw_resources_t and dq_dma_available_t structures are defined in the <sys/dma.h> as follows:

typedef struct dq_ddw_resources
	{   /* input by caller */
       uint64_t dqdr_version;
       /* returned to caller */
		 uint64_t dqdr_supported_page_sizes; 
		 uint64_t dqdr_windows_avail; 
       /* Amount of dynamic DMA windows available.
		  * If DDW_QUERY, is not available 
		  * 0 will be returned.
       */ 
        uint64_t dqdr_max_pages; /* Largest number of contiguous pages available.*/
    		uint64_t dqdr_rsvd1; 	        /* reserved for future use */
    		uint64_t dqdr_rsvd2;           /* reserved for future use */
    		uint64_t dqdr_rsvd3;           /* reserved for future use */
    		uint64_t dqdr_rsvd4;           /* reserved for future use */
	} dq_ddw_resources_t;
	/* 
 	* The dq_dma_available structure is to be used in d_map_querywith the 
 	* DMA_QUERY cmd specified
 	*/
	typedef struct dq_dma_available
	{
      /*input by caller */
      uint64_t dqda_version;
      uint64_t dqda_io_page_size; 
      /* Page size in bytes, should only be equal to the supported pagesize */
      /* returned to caller for DMA_Query*/
      uint64_t dqda_pages_available;
		uint64_t dqda_rsvd1;        /* reserved for future use */
		uint64_t dqda_rsvd2;        /* reserved for future use */
		uint64_t dqda_rsvd3;        /* reserved for future use */	
		uint64_t dqda_rsvd4;        /* reserved for future use */
	} dq_dma_available_t;

Execution Environment

The d_map_query kernel service can be called from the process environment only.

Return Values