sdk/2.1/docs/man/clCreate_memflagsInc.xml

    <!-- table 5.3 -->
    <informaltable frame="all">
      <tgroup cols="2" align="left" colsep="1" rowsep="1">
        <colspec colname="col1" colnum="1" />
        <thead>
          <row>
            <entry>cl_mem_flags</entry>
            <entry>Description</entry>
          </row>
        </thead>

        <tbody>
          <row>
            <entry><constant>CL_MEM_READ_WRITE</constant></entry>
            <entry>
              This flag specifies that the memory object will be read and written by a kernel. This
              is the default.
            </entry>
          </row>

          <row>
            <entry><constant>CL_MEM_WRITE_ONLY</constant></entry>
            <entry>
              <para>
                This flag specifies that the memory object will be written but not read by
                a kernel.
              </para>

              <para>
                Reading from a buffer or image object created with
                <constant>CL_MEM_WRITE_ONLY</constant> inside a kernel is undefined.
              </para>

              <para>
                <constant>CL_MEM_READ_WRITE</constant> and <constant>CL_MEM_WRITE_ONLY</constant>
                are mutually exclusive.
              </para>
            </entry>
          </row>

          <row>
            <entry><constant>CL_MEM_READ_ONLY</constant></entry>
            <entry>
              <para>
                This flag specifies that the memory object is a read-only memory object when
                used inside a kernel.
              </para>

              <para>
                Writing to a buffer or image object created with
                <constant>CL_MEM_READ_ONLY</constant> inside a kernel is undefined.
              </para>

              <para>
                <constant>CL_MEM_READ_WRITE</constant> or <constant>CL_MEM_WRITE_ONLY</constant>
                and <constant>CL_MEM_READ_ONLY</constant> are mutually exclusive.
              </para>
            </entry>
          </row>

          <row>
            <entry><constant>CL_MEM_USE_HOST_PTR</constant></entry>
            <entry>
              <para>
                This flag is valid only if <varname>host_ptr</varname> is not NULL. If
                specified, it indicates that the application wants the OpenCL implementation
                to use memory referenced by <varname>host_ptr</varname> as the storage bits
                for the memory object.
              </para>

              <para>
                OpenCL implementations are allowed to cache the buffer contents pointed to by
                <varname>host_ptr</varname> in device memory. This cached copy can be used when
                kernels are executed on a device.
              </para>

              <para>
                The result of OpenCL commands that operate on multiple buffer objects created with
                the same <varname>host_ptr</varname> or overlapping host regions is considered
                to be undefined.
              </para>

              <!-- Can't find this text in the 2.1 specs. <para>
                Refer to the <citerefentry href="dataTypes"> <refentrytitle>description
                of the alignment rules</refentrytitle> </citerefentry> for
                <varname>host_ptr</varname> for memory objects (buffer and images) created
                using <constant>CL_MEM_USE_HOST_PTR</constant>.
              </para> -->
            </entry>
          </row>

          <row>
            <entry><constant>CL_MEM_ALLOC_HOST_PTR</constant></entry>
            <entry>
              <para>
                This flag specifies that the application wants the OpenCL implementation to
                allocate memory from host accessible memory.
              </para>

              <para>
                <constant>CL_MEM_ALLOC_HOST_PTR</constant> and
                <constant>CL_MEM_USE_HOST_PTR</constant> are mutually exclusive.
              </para>
            </entry>
          </row>

          <row>
            <entry><constant>CL_MEM_COPY_HOST_PTR</constant></entry>
            <entry>
              <para>
                This flag is valid only if <varname>host_ptr</varname> is not NULL. If specified,
                it indicates that the application wants the OpenCL implementation to allocate
                memory for the memory object and copy the data from memory referenced by
                <varname>host_ptr</varname>.
              </para>

              <para>
                <constant>CL_MEM_COPY_HOST_PTR</constant> and
                <constant>CL_MEM_USE_HOST_PTR</constant> are mutually exclusive.
              </para>

              <para>
                <constant>CL_MEM_COPY_HOST_PTR</constant> can be used with
                <constant>CL_MEM_ALLOC_HOST_PTR</constant> to initialize the contents of the
                <type>cl_mem</type> object allocated using host-accessible (e.g.  PCIe) memory.
              </para>
            </entry>
          </row>

          <row>
            <entry><constant>CL_MEM_HOST_WRITE_ONLY</constant></entry>
            <entry>
              <para>
                This flag specifies that the host will only write to the memory object (using
                OpenCL APIs that enqueue a write or a map for write).  This can be used to optimize
                write access from the host (e.g. enable write-combined allocations for memory
                objects for devices that communicate with the host over a system bus such as PCIe).
              </para>
            </entry>
          </row>

          <row>
            <entry><constant>CL_MEM_HOST_READ_ONLY</constant></entry>
            <entry>
              <para>
                This flag specifies that the host will only read the memory object (using OpenCL
                APIs that enqueue a read or a map for read).
              </para>

              <para>
                <constant>CL_MEM_HOST_WRITE_ONLY</constant> and
                <constant>CL_MEM_HOST_READ_ONLY</constant> are mutually exclusive.
              </para>
            </entry>
          </row>

          <row>
            <entry><constant>CL_MEM_HOST_NO_ACCESS</constant></entry>
            <entry>
              <para>
                This flag specifies that the host will not read or write the memory object.
              </para>

              <para>
                <constant>CL_MEM_HOST_WRITE_ONLY</constant> or
                <constant>CL_MEM_HOST_READ_ONLY</constant> and
                <constant>CL_MEM_HOST_NO_ACCESS</constant> are mutually exclusive.
              </para>
            </entry>
          </row>
        </tbody>
      </tgroup>
    </informaltable>

<!-- 20-Oct-2015, API rev. 19 -->