SD_RW_DIRECT_ARGUMENT structure (sddef.h)

The SD_RW_DIRECT_ARGUMENT structure is used in conjunction with the SdBusSubmitRequest routine or the SdBusSubmitRequestAsync routine to send a Secure Digital (SD) read or write request to the bus driver.

Syntax

typedef struct _SD_RW_DIRECT_ARGUMENT {
  union {
    struct {
      ULONG Data : 8;
      ULONG Reserved1 : 1;
      ULONG Address : 17;
      ULONG Reserved2 : 1;
      ULONG ReadAfterWrite : 1;
      ULONG Function : 3;
      ULONG WriteToDevice : 1;
    } bits;
    ULONG AsULONG;
  } u;
} SD_RW_DIRECT_ARGUMENT, *PSD_RW_DIRECT_ARGUMENT;

Members

u

Name of union.

u.bits

Structure that contains the following members.

u.bits.Data

Contains eight bits of data to read or write.

u.bits.Reserved1

Reserved.

u.bits.Address

Indicates the address of the function space accessed by the operation.

u.bits.Reserved2

Reserved.

u.bits.ReadAfterWrite

Indicates that the operation should read the data at the specified location after writing to that location. The primary use of this option is to write to a control register and then read status information at the same address immediately afterwards. The caller must set WriteToDevice to 1 or this member will have no effect.

u.bits.Function

Contains the number of the function on the I/O card whose data space is accessed by the operation. A value of 0 indicates that the operation should address the common I/O area, rather than the I/O space of a particular card function.

To retrieve a function number for an SD device, a device driver must do the following:

1. Set the RequestFunction member of SDBUS_REQUEST_PACKET to an SD_REQUEST_FUNCTION enumerator value of SDRF_GET_PROPERTY.

2. Set the Property member of SDBUS_REQUEST_PACKET to SDP_FUNCTION_NUMBER.

3. Send the request to the bus driver by passing the initialized SDBUS_REQUEST_PACKET structure to either SdBusSubmitRequest or SdBusSubmitRequestAsync.

u.bits.WriteToDevice

Indicates a write operation when set to 1, and a read operation when set to 0.

u.AsULONG

Contains all 32 bits of the data stored in the preceding members, represented as a ULONG.

Requirements

See also

SdBusSubmitRequest

SdBusSubmitRequestAsync