<HTML ><HEAD ><TITLE >SG_SET_FORCE_LOW_DMA</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="Ioctl()s" HREF="ioctl.html"><LINK REL="PREVIOUS" TITLE="SG_SET_KEEP_ORPHAN (and _GET_)" HREF="gs_orphan.html"><LINK REL="NEXT" TITLE="SG_GET_LOW_DMA" HREF="g_lowdma.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="gs_orphan.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" >Chapter 8. Ioctl()s</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="g_lowdma.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="S_LOWDMA">8.7. SG_SET_FORCE_LOW_DMA</H1 ><DIV CLASS="FORMALPARA" ><P ><B >SG_SET_FORCE_LOW_DMA 0x2279. </B >Assumes 3rd argument points to an int containing 0 or 1. 0 (default) means sg decides whether to use memory above 16 Mbyte level (on i386) based on the host adapter being used by this SCSI device. Typically PCI SCSI adapters will indicate they can DMA to the whole 32 bit address space. If 1 is given then the host adapter is overridden and only memory below the 16MB level is used for DMA. A requirement for this should be extremely rare. If the "reserved" buffer allocated on open() is not in use then it will be de-allocated and re-allocated under the 16MB level (and the latter operation could fail yielding ENOMEM). Only the current file descriptor is affected.</P ></DIV ></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="gs_orphan.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="g_lowdma.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >SG_SET_KEEP_ORPHAN (and _GET_)</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="ioctl.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >SG_GET_LOW_DMA</TD ></TR ></TABLE ></DIV ></BODY ></HTML >