1 <html devsite> 2 <head> 3 <title>Error and stream handling</title> 4 <meta name="project_path" value="/_project.yaml" /> 5 <meta name="book_path" value="/_book.yaml" /> 6 </head> 7 <body> 8 <!-- 9 Copyright 2017 The Android Open Source Project 10 11 Licensed under the Apache License, Version 2.0 (the "License"); 12 you may not use this file except in compliance with the License. 13 You may obtain a copy of the License at 14 15 http://www.apache.org/licenses/LICENSE-2.0 16 17 Unless required by applicable law or agreed to in writing, software 18 distributed under the License is distributed on an "AS IS" BASIS, 19 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 20 See the License for the specific language governing permissions and 21 limitations under the License. 22 --> 23 24 25 26 <h2 id="error-mgmt">Error management</h2> 27 <p>Camera HAL device ops functions that have a return value will all return <code>-ENODEV 28 / NULL</code> in case of a serious error. This means the device cannot continue 29 operation and must be closed by the framework. Once this error is returned by 30 some method, or if <code>notify()</code> is called with <code>ERROR_DEVICE</code>, only the <code>close()</code> method 31 can be called successfully. All other methods will return <code>-ENODEV / NULL</code>.</p> 32 <p>If a device op is called in the wrong sequence, for example if the framework 33 calls <code>configure_streams()</code> before <code>initialize()</code>, the device must return 34 <code>-ENOSYS</code> from the call, and do nothing.</p> 35 <p>Transient errors in image capture must be reported through <code>notify()</code> as follows:</p> 36 <ul> 37 <li>The failure of an entire capture to occur must be reported by the HAL by 38 calling <code>notify()</codE> with <code>ERROR_REQUEST</code>. Individual errors for the result metadata 39 or the output buffers must not be reported in this case.</li> 40 <li>If the metadata for a capture cannot be produced, but some image buffers were 41 filled, the HAL must call <code>notify()</code> with <code>ERROR_RESULT</code>.</li> 42 <li>If an output image buffer could not be filled, but either the metadata was 43 produced or some other buffers were filled, the HAL must call <code>notify()</code> with 44 <code>ERROR_BUFFER</code> for each failed buffer.</li> 45 </ul> 46 <p>In each of these transient failure cases, the HAL must still call 47 <code>process_capture_result</code>, with valid output <code>buffer_handle_t</code>. If the result 48 metadata could not be produced, it should be <code>NULL</code>. If some buffers could not be 49 filled, their sync fences must be set to the error state.</p> 50 <p>Invalid input arguments result in <code>-EINVAL</code> from the appropriate methods. In that 51 case, the framework must act as if that call had never been made.</p> 52 <h2 id="stream-mgmt">Stream management</h2> 53 <h3 id="configure_streams">configure_streams</h3> 54 <p>Reset the HAL camera device processing pipeline and set up new input and output 55 streams. This call replaces any existing stream configuration with the streams 56 defined in the <code>stream_list</code>. This method will be called at least once after 57 <code>initialize()</code> before a request is submitted with <code>process_capture_request()</code>.</p> 58 <p>The <code>stream_list</code> must contain at least one output-capable stream, and may not 59 contain more than one input-capable stream. 60 The <code>stream_list</code> may contain streams that are also in the currently-active set of 61 streams (from the previous call to <code>configure_stream()</code>). These streams will 62 already have valid values for usage, maxbuffers, and the private pointer. If 63 such a stream has already had its buffers registered, <code>register_stream_buffers()</code> 64 will not be called again for the stream, and buffers from the stream can be 65 immediately included in input requests.</p> 66 <p>If the HAL needs to change the stream configuration for an existing stream due 67 to the new configuration, it may rewrite the values of usage and/or maxbuffers 68 during the configure call. The framework will detect such a change, and will 69 then reallocate the stream buffers, and call <code>register_stream_buffers()</code> again 70 before using buffers from that stream in a request.</p> 71 <p>If a currently-active stream is not included in <code>stream_list</code>, the HAL may safely 72 remove any references to that stream. It will not be reused in a later 73 <code>configure()</code> call by the framework, and all the gralloc buffers for it will be 74 freed after the <code>configure_streams()</code> call returns.</p> 75 <p>The <code>stream_list</code> structure is owned by the framework, and may not be accessed 76 once this call completes. The address of an individual <code>camera3streamt</code> 77 structure will remain valid for access by the HAL until the end of the first 78 <code>configure_stream()</code> call which no longer includes that <code>camera3streamt</code> in the 79 <code>stream_list</code> argument. The HAL may not change values in the stream structure 80 outside of the private pointer, except for the usage and maxbuffers members 81 during the <code>configure_streams()</code> call itself.</p> 82 <p>If the stream is new, the usage, maxbuffer, and private pointer fields of the 83 stream structure will all be set to 0. The HAL device must set these fields 84 before the <code>configure_streams()</code> call returns. These fields are then used by the 85 framework and the platform gralloc module to allocate the gralloc buffers for 86 each stream.</p> 87 <p>Before such a new stream can have its buffers included in a capture request, the 88 framework will call <code>register_stream_buffers()</code> with that stream. However, the 89 framework is not required to register buffers for _all streams before 90 submitting a request. This allows for quick startup of (for example) a preview 91 stream, with allocation for other streams happening later or concurrently.</p> 92 <h4><strong>Preconditions</strong></h4> 93 <p>The framework will only call this method when no captures are being processed. 94 That is, all results have been returned to the framework, and all in-flight 95 input and output buffers have been returned and their release sync fences have 96 been signaled by the HAL. The framework will not submit new requests for capture 97 while the <code>configure_streams()</code> call is underway.</p> 98 <h4><strong>Postconditions</strong></h4> 99 <p>The HAL device must configure itself to provide maximum possible output frame 100 rate given the sizes and formats of the output streams, as documented in the 101 camera device's static metadata.</p> 102 <h4><strong>Performance expectations</strong></h4> 103 <p>This call is expected to be heavyweight and possibly take several hundred 104 milliseconds to complete, since it may require resetting and reconfiguring the 105 image sensor and the camera processing pipeline. Nevertheless, the HAL device 106 should attempt to minimize the reconfiguration delay to minimize the 107 user-visible pauses during application operational mode changes (such as 108 switching from still capture to video recording).</p> 109 <h4><strong>Return values</strong></h4> 110 <ul> 111 <li><code>0</code>: On successful stream configuration</li> 112 <li><code>undefined</code></li> 113 <li><code>-EINVAL</code>: If the requested stream configuration is invalid. Some examples of 114 invalid stream configurations include: 115 <ul> 116 <li>Including more than 1 input-capable stream (<code>INPUT</code> or <code>BIDIRECTIONAL</code>)</li> 117 <li>Not including any output-capable streams (<code>OUTPUT</code> or <code>BIDIRECTIONAL</code>)</li> 118 <li>Including streams with unsupported formats, or an unsupported size for 119 that format.</li> 120 <li>Including too many output streams of a certain format.</li> 121 <li>Note that the framework submitting an invalid stream configuration is not 122 normal operation, since stream configurations are checked before 123 configure. An invalid configuration means that a bug exists in the 124 framework code, or there is a mismatch between the HAL's static metadata 125 and the requirements on streams.</li> 126 </ul> 127 </li> 128 <li><code>-ENODEV</code>: If there has been a fatal error and the device is no longer 129 operational. Only <code>close()</code> can be called successfully by the framework after 130 this error is returned.</li> 131 </ul> 132 <h3 id="register-stream">register_stream_buffers</h3> 133 <p>Register buffers for a given stream with the HAL device. This method is called 134 by the framework after a new stream is defined by <code>configure_streams</code>, and before 135 buffers from that stream are included in a capture request. If the same stream 136 is listed in a subsequent <code>configure_streams()</code> call, <code>register_stream_buffers</code> will 137 not be called again for that stream.</p> 138 <p>The framework does not need to register buffers for all configured streams 139 before it submits the first capture request. This allows quick startup for 140 preview (or similar use cases) while other streams are still being allocated.</p> 141 <p>This method is intended to allow the HAL device to map or otherwise prepare the 142 buffers for later use. The buffers passed in will already be locked for use. At 143 the end of the call, all the buffers must be ready to be returned to the stream. 144 The bufferset argument is only valid for the duration of this call.</p> 145 <p>If the stream format was set to <code>HAL_PIXEL_FORMAT_IMPLEMENTATION_DEFINED</code>, the 146 camera HAL should inspect the passed-in buffers here to determine any 147 platform-private pixel format information.</p> 148 <h4><strong>Return values</strong></h4> 149 <ul> 150 <li><code>0</code>: On successful registration of the new stream buffers</li> 151 <li><code>-EINVAL</code>: If the streambufferset does not refer to a valid active stream, or 152 if the buffers array is invalid.</li> 153 <li><code>-ENOMEM</code>: If there was a failure in registering the buffers. The framework must 154 consider all the stream buffers to be unregistered, and can try to register 155 again later.</li> 156 <li><code>-ENODEV</code>: If there is a fatal error, and the device is no longer operational. 157 Only <code>close()</code> can be called successfully by the framework after this error is 158 returned.</li> 159 </ul> 160 161 </body> 162 </html> 163
