<HTML ><HEAD ><TITLE >dxferp</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ "><LINK REL="HOME" TITLE="The Linux SCSI Generic (sg) HOWTO" HREF="index.html"><LINK REL="UP" TITLE="The sg_io_hdr_t structure in detail" HREF="sg_io_hdr_t.html"><LINK REL="PREVIOUS" TITLE="dxfer_len" HREF="x198.html"><LINK REL="NEXT" TITLE="cmdp" HREF="x209.html"></HEAD ><BODY CLASS="SECT1" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >The Linux SCSI Generic (sg) HOWTO</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="x198.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" >Chapter 6. The sg_io_hdr_t structure in detail</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="x209.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="AEN204">6.7. dxferp</H1 ><P > If 'iovec_count' is zero then this value is a pointer to user memory of at least 'dxfer_len' bytes in length. If there is a data transfer associated with the command then the data will be transferred to or from this user memory. If 'iovec_count' is greater than zero then this value points to a scatter-gather array in user memory. Each element of this array should be an object of type sg_iovec_t. Note that data is sometimes written to user memory (e.g. from a failed SCSI READ) even when an error has occurred.</P ><P >If mmap-ed IO is selected then the value in 'dxferp' is ignored and any data transfers will be to and from the address returned by the prior mmap() call.</P ><P >The type of dxferp is void * .</P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="x198.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="x209.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >dxfer_len</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="sg_io_hdr_t.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >cmdp</TD ></TR ></TABLE ></DIV ></BODY ></HTML >