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| <title>reserve_read_pipe</title> |
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| <body> |
| <div class="refentry"> |
| <a id="id-1"></a> |
| <div class="titlepage"></div> |
| <div xmlns="" class="refnamediv"> |
| <a xmlns="http://www.w3.org/1999/xhtml" id="reserve_read_pipe"></a> |
| <h1>reserve_read_pipe</h1> |
| <p> |
| Reserve entries for reading from pipe. |
| </p> |
| </div> |
| <div class="refsynopsisdiv"> |
| <h2></h2> |
| <div class="funcsynopsis"> |
| <table xmlns="" border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"> |
| <tr valign="bottom"> |
| <td> |
| <code xmlns="http://www.w3.org/1999/xhtml" class="funcdef"> |
| <a class="link" href="enums.html#reserve_id_t" target="pagedisplay">reserve_id_t</a> |
| <strong class="fsfunc"> |
| reserve_read_pipe |
| </strong> |
| (</code> |
| <td>read_only pipe gentype <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">p</var>, </td> |
| </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td><a xmlns="http://www.w3.org/1999/xhtml" class="link" href="scalarDataTypes.html" target="pagedisplay">uint</a> <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">num_packets</var><code>)</code></td> |
| </tr> |
| </table> |
| </div> |
| </div> |
| <div class="refsect1"> |
| <a id="description"></a> |
| <h2>Description</h2> |
| <p> |
| Reserve <code class="varname">num_packets</code> entries for reading from |
| pipe <code class="varname">p</code>. Returns a valid |
| reservation ID if the reservation is successful. |
| </p> |
| <p> |
| We use the generic type name gentype to indicate the built-in |
| OpenCL C scalar or vector integer or floating-point data types or any user defined type built |
| from these scalar and vector data types can be used as the type for the arguments to the pipe |
| functions listed in this section. |
| The half scalar and vector types can only be used if the |
| <a class="citerefentry" href="cl_khr_fp16.html"><span class="citerefentry"><span class="refentrytitle">cl_khr_fp16</span></span></a> |
| extension is supported. The <span class="type">double</span> scalar |
| and vector types can only be used if double precision is supported. |
| </p> |
| <h4><a id="id-1.5.4"></a>General information about pipes</h4> |
| <p> |
| A pipe is identified by specifying the <code class="code">pipe</code> |
| keyword with a type. The data type specifies the |
| size of each packet in the pipe. The <code class="code">pipe</code> |
| keyword is a type modifier. When it is applied to |
| another type <code class="code">T</code>, the result is a pipe type |
| whose elements (or packets) are of type <code class="code">T</code>. The packet |
| type <code class="code">T</code> may be any supported OpenCL C scalar |
| and vector integer or floating-point data types, or |
| a user-defined type built from these scalar and vector data types. |
| </p> |
| <p> |
| The |
| <a class="citerefentry" href="qualifiers.html"><span class="citerefentry"><span class="refentrytitle">read_only</span></span></a> |
| (or <code class="code">__read_only</code>) and |
| <a class="citerefentry" href="qualifiers.html"><span class="citerefentry"><span class="refentrytitle">write_only</span></span></a> |
| (or <code class="code">__write_only</code>) qualifiers |
| must be used with the pipe qualifier when a pipe |
| is a parameter of a kernel or of a user-defined |
| function to identify if a pipe can be read from |
| or written to by a kernel and its callees and |
| enqueued child kernels. If no qualifier is specified, |
| <a class="citerefentry" href="qualifiers.html"><span class="citerefentry"><span class="refentrytitle">read_only</span></span></a> |
| is assumed. |
| </p> |
| <p> |
| A kernel cannot read from and write to the same pipe object. Using the |
| <a class="citerefentry" href="qualifiers.html"><span class="citerefentry"><span class="refentrytitle">read_write </span></span></a> |
| (or <code class="code">__read_write</code>) qualifier with the pipe qualifier is a compilation error. |
| </p> |
| <p> |
| The macro <code class="constant">CLK_NULL_RESERVE_ID</code> refers to an invalid reservation ID. |
| </p> |
| <p> |
| NOTE: The |
| <a class="citerefentry" href="read_pipe.html"><span class="citerefentry"><span class="refentrytitle">read_pipe</span></span></a> and |
| <a class="citerefentry" href="write_pipe.html"><span class="citerefentry"><span class="refentrytitle">write_pipe</span></span></a> |
| functions that take a reservation ID as an argument can |
| be used to read from or write to a packet index. These built-ins can be used to read from or write |
| to a packet index one or multiple times. If a packet index that is reserved for writing is not |
| written to using the |
| <a class="citerefentry" href="write_pipe.html"><span class="citerefentry"><span class="refentrytitle">write_pipe</span></span></a> |
| function, the contents of that packet in the pipe are undefined. |
| <a class="citerefentry" href="commit_read_pipe.html"><span class="citerefentry"><span class="refentrytitle">commit_read_pipe</span></span></a> and |
| <a class="citerefentry" href="work_group_commit_read_pipe.html"><span class="citerefentry"><span class="refentrytitle">work_group_commit_read_pipe</span></span></a> |
| remove the entries reserved for reading from the pipe. |
| <a class="citerefentry" href="commit_write_pipe.html"><span class="citerefentry"><span class="refentrytitle">commit_write_pipe</span></span></a> and |
| <a class="citerefentry" href="work_group_commit_write_pipe.html"><span class="citerefentry"><span class="refentrytitle">work_group_commit_write_pipe</span></span></a> |
| ensures that the entries reserved for writing are all added in-order |
| as one contiguous set of packets to the pipe. |
| </p> |
| <p> |
| There can only be <code class="constant">CL_DEVICE_PIPE_MAX_ACTIVE_RESERVATIONS</code> |
| (refer to the list of possible values for <code class="varname">parame_name</code> |
| for <a class="citerefentry" href="clGetDeviceInfo.html"><span class="citerefentry"><span class="refentrytitle">clGetDeviceInfo</span></span></a>(table 4.3)) |
| reservations active (i.e. reservation IDs that have been reserved |
| but not committed) per work-item or work-group for a |
| pipe in a kernel executing on a device. |
| </p> |
| <p> |
| Work-item based reservations made by a work-item are ordered in the pipe as they are ordered in |
| the program. Reservations made by different work-items that belong to the same work-group |
| can be ordered using the work-group barrier function. The order of work-item based |
| reservations that belong to different work-groups is implementation defined. |
| </p> |
| <p> |
| Work-group based reservations made by a work-group are ordered in the pipe as they are ordered |
| in the program. The order of work-group based reservations by different work-groups is |
| implementation defined. |
| </p> |
| <h4><a id="id-1.5.13"></a>Restrictions</h4> |
| <p> |
| Pipes can only be passed as arguments to a function |
| (including kernel functions). The C |
| <a class="citerefentry" href="operators.html"><span class="citerefentry"><span class="refentrytitle">operators</span></span></a> |
| (refer to section 6.3 of the OpenCL 2.0 specification) cannot be used with |
| variables declared with the <code class="code">pipe</code> qualifier. |
| </p> |
| <p> |
| The <code class="code">pipe</code> qualifier cannot be used with |
| variables declared inside a kernel, a structure or |
| union field, a pointer type, an array, global variables |
| declared in program scope or the return type of a function. |
| </p> |
| <p> |
| The following behavior is undefined: |
| </p> |
| <p> |
| </p> |
| <div class="itemizedlist"> |
| <ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| A kernel fails to call |
| <code class="function">reserve_pipe</code> |
| before calling |
| <a class="citerefentry" href="read_pipe.html"><span class="citerefentry"><span class="refentrytitle">read_pipe</span></span></a> or |
| <a class="citerefentry" href="write_pipe.html"><span class="citerefentry"><span class="refentrytitle">write_pipe</span></span></a> that take a |
| reservation ID. |
| </li> |
| <li class="listitem"> |
| A kernel calls |
| <a class="citerefentry" href="read_pipe.html"><span class="citerefentry"><span class="refentrytitle">read_pipe</span></span></a>, |
| <a class="citerefentry" href="write_pipe.html"><span class="citerefentry"><span class="refentrytitle">write_pipe</span></span></a>, |
| <a class="citerefentry" href="commit_read_pipe.html"><span class="citerefentry"><span class="refentrytitle">commit_read_pipe</span></span></a> or |
| <a class="citerefentry" href="commit_write_pipe.html"><span class="citerefentry"><span class="refentrytitle">commit_write_pipe</span></span></a> with |
| an invalid reservation ID. |
| </li> |
| <li class="listitem"> |
| A kernel calls |
| <a class="citerefentry" href="read_pipe.html"><span class="citerefentry"><span class="refentrytitle">read_pipe</span></span></a> or |
| <a class="citerefentry" href="write_pipe.html"><span class="citerefentry"><span class="refentrytitle">write_pipe</span></span></a> |
| with an valid reservation ID but with an <code class="varname">index</code> |
| that is not a value from 0 ... <code class="varname">num_packets</code> - 1 |
| specified to the corresponding call to |
| <code class="function">reserve_pipe</code>. |
| </li> |
| <li class="listitem"> |
| A kernel calls |
| <a class="citerefentry" href="read_pipe.html"><span class="citerefentry"><span class="refentrytitle">read_pipe</span></span></a> or |
| <a class="citerefentry" href="write_pipe.html"><span class="citerefentry"><span class="refentrytitle">write_pipe</span></span></a> |
| with a reservation ID that has already been committed (i.e. a |
| <a class="citerefentry" href="commit_read_pipe.html"><span class="citerefentry"><span class="refentrytitle">commit_read_pipe</span></span></a> or |
| <a class="citerefentry" href="commit_write_pipe.html"><span class="citerefentry"><span class="refentrytitle">commit_write_pipe</span></span></a> |
| with this reservation ID has |
| already been called). |
| </li> |
| <li class="listitem"> |
| A kernel fails to call |
| <a class="citerefentry" href="commit_read_pipe.html"><span class="citerefentry"><span class="refentrytitle">commit_read_pipe</span></span></a> |
| for any reservation ID obtained by a prior call |
| to <a class="citerefentry" href="reserve_read_pipe.html"><span class="citerefentry"><span class="refentrytitle">reserve_read_pipe</span></span></a>. |
| </li> |
| <li class="listitem"> |
| A kernel fails to call |
| <a class="citerefentry" href="commit_write_pipe.html"><span class="citerefentry"><span class="refentrytitle">commit_write_pipe</span></span></a> |
| for any reservation ID obtained by a prior call |
| to <a class="citerefentry" href="reserve_write_pipe.html"><span class="citerefentry"><span class="refentrytitle">reserve_write_pipe</span></span></a>. |
| </li> |
| <li class="listitem"> |
| The contents of the reserved data packets in the pipe are undefined if the kernel does not |
| call <a class="citerefentry" href="write_pipe.html"><span class="citerefentry"><span class="refentrytitle">write_pipe</span></span></a> |
| for all entries that were reserved by the corresponding call to |
| <code class="function">reserve_pipe</code>. |
| </li> |
| <li class="listitem"> |
| Calls to |
| <a class="citerefentry" href="read_pipe.html"><span class="citerefentry"><span class="refentrytitle">read_pipe</span></span></a> |
| that takes a reservation ID and |
| <a class="citerefentry" href="commit_read_pipe.html"><span class="citerefentry"><span class="refentrytitle">commit_read_pipe</span></span></a> or |
| <a class="citerefentry" href="write_pipe.html"><span class="citerefentry"><span class="refentrytitle">write_pipe</span></span></a> that |
| takes a reservation ID and |
| <a class="citerefentry" href="commit_write_pipe.html"><span class="citerefentry"><span class="refentrytitle">commit_write_pipe</span></span></a> |
| for a given reservation ID must be called |
| by the same kernel that made the reservation using |
| <a class="citerefentry" href="reserve_read_pipe.html"><span class="citerefentry"><span class="refentrytitle">reserve_read_pipe</span></span></a> or |
| <a class="citerefentry" href="reserve_write_pipe.html"><span class="citerefentry"><span class="refentrytitle">reserve_write_pipe</span></span></a>. |
| The reservation ID cannot be passed to another kernel including |
| child kernels. |
| </li> |
| </ul> |
| </div> |
| <p> |
| </p> |
| <div class="refsect2"> |
| <a id="example1"></a> |
| <h3> |
| Example |
| </h3> |
| <p> |
| In the following example |
| </p> |
| <div class="informaltable"> |
| <table class="informaltable" border="0"> |
| <colgroup> |
| <col align="left" class="col1" /> |
| </colgroup> |
| <tbody> |
| <tr> |
| <td align="left"> |
| kernel void |
| foo (read_only pipe fooA_t pipeA, |
| write_only pipe fooB_t pipeB) |
| { |
| ... |
| } |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <p> |
| <code class="code">pipeA</code> is a read-only pipe object, |
| and <code class="code">pipeB</code> is a write-only pipe object. |
| </p> |
| </div> |
| </div> |
| <div class="refsect1"> |
| <a id="specification"></a> |
| <h2>Specification</h2> |
| <p> |
| <img src="pdficon_small1.gif" /> |
| |
| <a href="https://www.khronos.org/registry/cl/specs/opencl-2.0-openclc.pdf#namedest=reserve_read_pipe" target="OpenCL Spec">OpenCL Specification</a> |
| </p> |
| </div> |
| <div class="refsect1"> |
| <a id="seealso"></a> |
| <h2>Also see</h2> |
| <p> |
| <a class="citerefentry" href="pipeFunctions.html"><span class="citerefentry"><span class="refentrytitle">Pipe Functions</span></span></a> |
| </p> |
| </div> |
| <div xmlns="" class="refsect3" lang="en" xml:lang="en"><a xmlns="http://www.w3.org/1999/xhtml" id="Copyright"></a><h4 xmlns="http://www.w3.org/1999/xhtml"></h4><img xmlns="http://www.w3.org/1999/xhtml" src="KhronosLogo.jpg" /><p xmlns="http://www.w3.org/1999/xhtml"></p>Copyright © 2007-2015 The Khronos Group Inc. |
| Permission is hereby granted, free of charge, to any person obtaining a |
| copy of this software and/or associated documentation files (the |
| "Materials"), to deal in the Materials without restriction, including |
| without limitation the rights to use, copy, modify, merge, publish, |
| distribute, sublicense, and/or sell copies of the Materials, and to |
| permit persons to whom the Materials are furnished to do so, subject to |
| the condition that this copyright notice and permission notice shall be included |
| in all copies or substantial portions of the Materials. |
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