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<!-- Copyright (C) 2003 Red Hat, Inc. --> <!-- This material may be distributed only subject to the terms --> <!-- and conditions set forth in the Open Publication License, v1.0 --> <!-- or later (the latest version is presently available at --> <!-- http://www.opencontent.org/openpub/). --> <!-- Distribution of the work or derivative of the work in any --> <!-- standard (paper) book form is prohibited unless prior --> <!-- permission is obtained from the copyright holder. --> <HTML ><HEAD ><TITLE >Synchronization Levels</TITLE ><meta name="MSSmartTagsPreventParsing" content="TRUE"> <META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+ "><LINK REL="HOME" TITLE="eCos Reference Manual" HREF="ecos-ref.html"><LINK REL="UP" TITLE="Device Driver Interface to the Kernel" HREF="devapi-device-driver-interface-to-the-kernel.html"><LINK REL="PREVIOUS" TITLE="Device Driver Models" HREF="devapi-device-driver-models.html"><LINK REL="NEXT" TITLE="The API" HREF="devapi-api.html"></HEAD ><BODY CLASS="SECTION" 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" >eCos Reference Manual</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="devapi-device-driver-models.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" >Chapter 18. Device Driver Interface to the Kernel</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="devapi-api.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECTION" ><H1 CLASS="SECTION" ><A NAME="DEVAPI-SYNCHRONIZATION-LEVELS">Synchronization Levels</H1 ><P >Since it would be dangerous for an ISR or DSR to make a call that might reschedule the current thread (by trying to lock a mutex for example) all functions in this API have an associated synchronization level. These levels are:</P ><P ></P ><DIV CLASS="VARIABLELIST" ><DL ><DT >Thread</DT ><DD ><P > This function may only be called from within threads. This is usually the client code that makes calls into the device driver. In a non-kernel configuration, this will be code running at the default non-interrupt level. </P ></DD ><DT >DSR</DT ><DD ><P > This function may be called by either DSR or thread code. </P ></DD ><DT >ISR</DT ><DD ><P > This function may be called from ISR, DSR or thread code. </P ></DD ></DL ></DIV ><P >The following table shows, for each API function, the levels at which is may be called:</P ><TABLE BORDER="5" BGCOLOR="#E0E0F0" WIDTH="70%" ><TR ><TD ><PRE CLASS="PROGRAMLISTING" > Callable from: Function ISR DSR Thread ------------------------------------------------------------------------- cyg_drv_isr_lock X X X cyg_drv_isr_unlock X X X cyg_drv_spinlock_init X cyg_drv_spinlock_destroy X cyg_drv_spinlock_spin X X X cyg_drv_spinlock_clear X X X cyg_drv_spinlock_try X X X cyg_drv_spinlock_test X X X cyg_drv_spinlock_spin_intsave X X X cyg_drv_spinlock_clear_intsave X X X cyg_drv_dsr_lock X X cyg_drv_dsr_unlock X X cyg_drv_mutex_init X cyg_drv_mutex_destroy X cyg_drv_mutex_lock X cyg_drv_mutex_trylock X cyg_drv_mutex_unlock X cyg_drv_mutex_release X cyg_drv_cond_init X cyg_drv_cond_destroy X cyg_drv_cond_wait X cyg_drv_cond_signal X X cyg_drv_cond_broadcast X X cyg_drv_interrupt_create X cyg_drv_interrupt_delete X cyg_drv_interrupt_attach X X X cyg_drv_interrupt_detach X X X cyg_drv_interrupt_mask X X X cyg_drv_interrupt_unmask X X X cyg_drv_interrupt_acknowledge X X X cyg_drv_interrupt_configure X X X cyg_drv_interrupt_level X X X cyg_drv_interrupt_set_cpu X X X cyg_drv_interrupt_get_cpu X X X </PRE ></TD ></TR ></TABLE ></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="devapi-device-driver-models.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="ecos-ref.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="devapi-api.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Device Driver Models</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="devapi-device-driver-interface-to-the-kernel.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >The API</TD ></TR ></TABLE ></DIV ></BODY ></HTML >
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