DISK_IOCTL_READ

Block device drivers respond to this I/O control code in order to service FAT file system requests to read data from the block device.

Parameters

hDevice

Handle to the block device.

dwIoControlCode

DISK_IOCTL_READ.

lpInBuffer

Address of a SG_REQ structure..

nInBufferSize

Size of a SG_REQ structure.

lpOutBuffer

Not used.

nOutBufferSize

Not used.

lpBytesReturned

Address of a DWORD to receive total bytes returned.

lpOverlapped

Not used.

Return Values

When this function returns, the FAT file system expects the sr_status member of the SG_REQ structure to be set to either ERROR_SUCCESS if the read succeeded, or a standard Win32 error code otherwise. Certain errors are automatically retried, such as ERROR_BAD_UNIT if the device has been removed and ERROR_NOT_READY if the driver is in the process of shutting down or starting up. Block device drivers should return ERROR_GEN_FAILURE for any unknown or unexpected errors.

Remarks

The FAT file system fills in the SG_REQ structure passed to the block device driver as follows:

sr_start

Starting block number.

sr_num_sec

Number of blocks to read.

sr_num_sg

Number of scatter/gather buffers (normally 1).

sr_callback

NULL.

sr_sglist[0].sb_buf

Address of the buffer to read blocks into. Note that this buffer is unaligned.

sr_sglist[0].sb_len

Size of the sr_sglist[0].sb_buf buffer in bytes.

If sr_num_sg is greater than 1, then the block device driver should fill in additional entries in the sr_sglist array.