1 page.title=Error and stream handling 2 @jd:body 3 4 <!-- 5 Copyright 2013 The Android Open Source Project 6 7 Licensed under the Apache License, Version 2.0 (the "License"); 8 you may not use this file except in compliance with the License. 9 You may obtain a copy of the License at 10 11 http://www.apache.org/licenses/LICENSE-2.0 12 13 Unless required by applicable law or agreed to in writing, software 14 distributed under the License is distributed on an "AS IS" BASIS, 15 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 See the License for the specific language governing permissions and 17 limitations under the License. 18 --> 19 <div id="qv-wrapper"> 20 <div id="qv"> 21 <h2>In this document</h2> 22 <ol id="auto-toc"> 23 </ol> 24 </div> 25 </div> 26 27 <h2 id="error-mgmt">Error management</h2> 28 <p>Camera HAL device ops functions that have a return value will all return -ENODEV 29 / NULL in case of a serious error. This means the device cannot continue 30 operation, and must be closed by the framework. Once this error is returned by 31 some method, or if notify() is called with ERROR_DEVICE, only the close() method 32 can be called successfully. All other methods will return -ENODEV / NULL.<br/> 33 If a device op is called in the wrong sequence, for example if the framework 34 calls configure_streams() is called before initialize(), the device must return 35 -ENOSYS from the call, and do nothing.<br/> 36 Transient errors in image capture must be reported through notify() as follows:</p> 37 <ul> 38 <li>The failure of an entire capture to occur must be reported by the HAL by 39 calling notify() with ERROR_REQUEST. Individual errors for the result metadata 40 or the output buffers must not be reported in this case.</li> 41 <li>If the metadata for a capture cannot be produced, but some image buffers were 42 filled, the HAL must call notify() with ERROR_RESULT.</li> 43 <li>If an output image buffer could not be filled, but either the metadata was 44 produced or some other buffers were filled, the HAL must call notify() with 45 ERROR_BUFFER for each failed buffer.</li> 46 </ul> 47 <p>In each of these transient failure cases, the HAL must still call 48 process_capture_result, with valid output buffer_handle_t. If the result 49 metadata could not be produced, it should be NULL. If some buffers could not be 50 filled, their sync fences must be set to the error state.<br/> 51 Invalid input arguments result in -EINVAL from the appropriate methods. In that 52 case, the framework must act as if that call had never been made.</p> 53 <h2 id="stream-mgmt">Stream management</h2> 54 <h3 id="configure_streams">configure_streams</h3> 55 <p>Reset the HAL camera device processing pipeline and set up new input and output 56 streams. This call replaces any existing stream configuration with the streams 57 defined in the stream_list. This method will be called at least once after 58 initialize() before a request is submitted with process_capture_request().<br/> 59 The stream_list must contain at least one output-capable stream, and may not 60 contain more than one input-capable stream.<br/> 61 The stream_list may contain streams that are also in the currently-active set of 62 streams (from the previous call to configure_stream()). These streams will 63 already have valid values for usage, maxbuffers, and the private pointer. If 64 such a stream has already had its buffers registered, register_stream_buffers() 65 will not be called again for the stream, and buffers from the stream can be 66 immediately included in input requests.<br/> 67 If the HAL needs to change the stream configuration for an existing stream due 68 to the new configuration, it may rewrite the values of usage and/or maxbuffers 69 during the configure call. The framework will detect such a change, and will 70 then reallocate the stream buffers, and call register_stream_buffers() again 71 before using buffers from that stream in a request.<br/> 72 If a currently-active stream is not included in stream_list, the HAL may safely 73 remove any references to that stream. It will not be reused in a later 74 configure() call by the framework, and all the gralloc buffers for it will be 75 freed after the configure_streams() call returns.<br/> 76 The stream_list structure is owned by the framework, and may not be accessed 77 once this call completes. The address of an individual camera3streamt 78 structure will remain valid for access by the HAL until the end of the first 79 configure_stream() call which no longer includes that camera3streamt in the 80 stream_list argument. The HAL may not change values in the stream structure 81 outside of the private pointer, except for the usage and maxbuffers members 82 during the configure_streams() call itself.<br/> 83 If the stream is new, the usage, maxbuffer, and private pointer fields of the 84 stream structure will all be set to 0. The HAL device must set these fields 85 before the configure_streams() call returns. These fields are then used by the 86 framework and the platform gralloc module to allocate the gralloc buffers for 87 each stream.<br/> 88 Before such a new stream can have its buffers included in a capture request, the 89 framework will call register_stream_buffers() with that stream. However, the 90 framework is not required to register buffers for _all streams before 91 submitting a request. This allows for quick startup of (for example) a preview 92 stream, with allocation for other streams happening later or concurrently.</p> 93 <h4><strong>Preconditions</strong></h4> 94 <p>The framework will only call this method when no captures are being processed. 95 That is, all results have been returned to the framework, and all in-flight 96 input and output buffers have been returned and their release sync fences have 97 been signaled by the HAL. The framework will not submit new requests for capture 98 while the configure_streams() call is underway.</p> 99 <h4><strong>Postconditions</strong></h4> 100 <p>The HAL device must configure itself to provide maximum possible output frame 101 rate given the sizes and formats of the output streams, as documented in the 102 camera device's static metadata.</p> 103 <h4><strong>Performance expectations</strong></h4> 104 <p>This call is expected to be heavyweight and possibly take several hundred 105 milliseconds to complete, since it may require resetting and reconfiguring the 106 image sensor and the camera processing pipeline. Nevertheless, the HAL device 107 should attempt to minimize the reconfiguration delay to minimize the 108 user-visible pauses during application operational mode changes (such as 109 switching from still capture to video recording).</p> 110 <h4><strong>Return values</strong></h4> 111 <ul> 112 <li>0: On successful stream configuration</li> 113 <li>undefined</li> 114 <li>-EINVAL: If the requested stream configuration is invalid. Some examples of 115 invalid stream configurations include: 116 <ul> 117 <li>Including more than 1 input-capable stream (INPUT or BIDIRECTIONAL)</li> 118 <li>Not including any output-capable streams (OUTPUT or BIDIRECTIONAL)</li> 119 <li>Including streams with unsupported formats, or an unsupported size for 120 that format.</li> 121 <li>Including too many output streams of a certain format.</li> 122 <li>Note that the framework submitting an invalid stream configuration is not 123 normal operation, since stream configurations are checked before 124 configure. An invalid configuration means that a bug exists in the 125 framework code, or there is a mismatch between the HAL's static metadata 126 and the requirements on streams.</li> 127 </ul> 128 </li> 129 <li>-ENODEV: If there has been a fatal error and the device is no longer 130 operational. Only close() can be called successfully by the framework after 131 this error is returned.</li> 132 </ul> 133 <h3 id="register-stream">register_stream_buffers</h3> 134 <p>Register buffers for a given stream with the HAL device. This method is called 135 by the framework after a new stream is defined by configure_streams, and before 136 buffers from that stream are included in a capture request. If the same stream 137 is listed in a subsequent configure_streams() call, register_stream_buffers will 138 not be called again for that stream.<br/> 139 The framework does not need to register buffers for all configured streams 140 before it submits the first capture request. This allows quick startup for 141 preview (or similar use cases) while other streams are still being allocated.<br/> 142 This method is intended to allow the HAL device to map or otherwise prepare the 143 buffers for later use. The buffers passed in will already be locked for use. At 144 the end of the call, all the buffers must be ready to be returned to the stream. 145 The bufferset argument is only valid for the duration of this call.<br/> 146 If the stream format was set to HAL_PIXEL_FORMAT_IMPLEMENTATION_DEFINED, the 147 camera HAL should inspect the passed-in buffers here to determine any 148 platform-private pixel format information.</p> 149 <h4><strong>Return values</strong></h4> 150 <ul> 151 <li>0: On successful registration of the new stream buffers</li> 152 <li>-EINVAL: If the streambufferset does not refer to a valid active stream, or 153 if the buffers array is invalid.</li> 154 <li>-ENOMEM: If there was a failure in registering the buffers. The framework must 155 consider all the stream buffers to be unregistered, and can try to register 156 again later.</li> 157 <li>-ENODEV: If there is a fatal error, and the device is no longer operational. 158 Only close() can be called successfully by the framework after this error is 159 returned.</li> 160 </ul> 161
