sdk/2.0/docs/man/map_flags_Inc.xml

    <!-- table 5.5, applies to clEnqueueMapBuffer.xml, clEnqueueMapImage.xml, clEnqueueSVMMap.xml -->

    <informaltable frame="all"><tgroup cols="2" align="left" colsep="1" rowsep="1">
        <colspec colname="col1" colnum="1" />
        <colspec colname="col2" colnum="2" />
        <thead>
            <row>
            <entry>cl_map_flags</entry>
            <entry>Description</entry>
            </row>
        </thead>

        <tbody>
            <row>
                <entry><constant>CL_MAP_READ</constant></entry>
                <entry>
                    <para>
                        This flag specifies that the region being mapped in the memory
                        object is being mapped for reading.
                    </para>

                    <para>
                        The pointer returned by 
                        <function>clEnqueueMap{Buffer|Image}</function>
                        is guaranteed to contain
                        the latest bits in the region being
                        mapped when the 
                        <function>clEnqueueMap{Buffer|Image}</function>
                        command has completed.
                    </para>
                </entry>
            </row>

            <row>
                <entry><constant>CL_MAP_WRITE</constant></entry>
                <entry>
                    <para>
                        This flag specifies that the region being mapped in the memory
                        object is being mapped for writing.
                    </para>

                    <para>
                        The pointer returned by 
                        <function>clEnqueueMap{Buffer|Image}</function>
                        is guaranteed to contain the latest bits in
                        the region being mapped when the 
                        <function>clEnqueueMap{Buffer|Image}</function>
                        command has completed.
                    </para>
                </entry>
            </row>

            <row>
                <entry><constant>CL_MAP_WRITE_INVALIDATE_REGION</constant></entry>
                <entry>
                    <para>
                        This flag specifies that the region being mapped in the memory
                        object is being mapped for writing.
                    </para>

                    <para>
                        The contents of the region being mapped are to be discarded.
                        This is typically the case
                        when the region being mapped is overwritten by the host. This
                        flag allows the implementation
                        to no longer guarantee that the pointer returned by
                        <function>clEnqueueMap{Buffer|Image}</function>
                        contains the latest bits in the region being
                        mapped which can be a significant performance enhancement.
                    </para>

                    <para>
                        <constant>CL_MAP_READ</constant> or <constant>CL_MAP_WRITE</constant>
                        and <constant> CL_MAP_WRITE_INVALIDATE_REGION</constant>
                        are mutually exclusive.
                    </para>
                </entry>
            </row>
        </tbody>
    </tgroup>
</informaltable>

<!-- 30-May-2013 -->