page.title=Error and stream handling
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    <h2>In this document</h2>
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<h2 id="error-mgmt">Error management</h2>
<p>Camera HAL device ops functions that have a return value will all return -ENODEV 
  / NULL in case of a serious error. This means the device cannot continue 
  operation, and must be closed by the framework. Once this error is returned by 
  some method, or if notify() is called with ERROR_DEVICE, only the close() method 
  can be called successfully. All other methods will return -ENODEV / NULL.<br/>
  If a device op is called in the wrong sequence, for example if the framework 
  calls configure_streams() is called before initialize(), the device must return 
  -ENOSYS from the call, and do nothing.<br/>
  Transient errors in image capture must be reported through notify() as follows:</p>
<ul>
  <li>The failure of an entire capture to occur must be reported by the HAL by 
    calling notify() with ERROR_REQUEST. Individual errors for the result metadata 
    or the output buffers must not be reported in this case.</li>
  <li>If the metadata for a capture cannot be produced, but some image buffers were 
    filled, the HAL must call notify() with ERROR_RESULT.</li>
  <li>If an output image buffer could not be filled, but either the metadata was 
    produced or some other buffers were filled, the HAL must call notify() with 
    ERROR_BUFFER for each failed buffer.</li>
</ul>
<p>In each of these transient failure cases, the HAL must still call 
  process_capture_result, with valid output buffer_handle_t. If the result 
  metadata could not be produced, it should be NULL. If some buffers could not be 
  filled, their sync fences must be set to the error state.<br/>
  Invalid input arguments result in -EINVAL from the appropriate methods. In that 
  case, the framework must act as if that call had never been made.</p>
<h2 id="stream-mgmt">Stream management</h2>
<h3 id="configure_streams">configure_streams</h3>
<p>Reset the HAL camera device processing pipeline and set up new input and output 
  streams. This call replaces any existing stream configuration with the streams 
  defined in the stream_list. This method will be called at least once after 
  initialize() before a request is submitted with process_capture_request().<br/>
  The stream_list must contain at least one output-capable stream, and may not 
  contain more than one input-capable stream.<br/>
  The stream_list may contain streams that are also in the currently-active set of 
  streams (from the previous call to configure_stream()). These streams will 
  already have valid values for usage, maxbuffers, and the private pointer. If 
  such a stream has already had its buffers registered, register_stream_buffers() 
  will not be called again for the stream, and buffers from the stream can be 
  immediately included in input requests.<br/>
  If the HAL needs to change the stream configuration for an existing stream due 
  to the new configuration, it may rewrite the values of usage and/or maxbuffers 
  during the configure call. The framework will detect such a change, and will 
  then reallocate the stream buffers, and call register_stream_buffers() again 
  before using buffers from that stream in a request.<br/>
  If a currently-active stream is not included in stream_list, the HAL may safely 
  remove any references to that stream. It will not be reused in a later 
  configure() call by the framework, and all the gralloc buffers for it will be 
  freed after the configure_streams() call returns.<br/>
  The stream_list structure is owned by the framework, and may not be accessed 
  once this call completes. The address of an individual camera3streamt 
  structure will remain valid for access by the HAL until the end of the first 
  configure_stream() call which no longer includes that camera3streamt in the 
  stream_list argument. The HAL may not change values in the stream structure 
  outside of the private pointer, except for the usage and maxbuffers members 
  during the configure_streams() call itself.<br/>
  If the stream is new, the usage, maxbuffer, and private pointer fields of the 
  stream structure will all be set to 0. The HAL device must set these fields 
  before the configure_streams() call returns. These fields are then used by the 
  framework and the platform gralloc module to allocate the gralloc buffers for 
  each stream.<br/>
  Before such a new stream can have its buffers included in a capture request, the 
  framework will call register_stream_buffers() with that stream. However, the 
  framework is not required to register buffers for _all streams before 
  submitting a request. This allows for quick startup of (for example) a preview 
  stream, with allocation for other streams happening later or concurrently.</p>
<h4><strong>Preconditions</strong></h4>
<p>The framework will only call this method when no captures are being processed. 
  That is, all results have been returned to the framework, and all in-flight 
  input and output buffers have been returned and their release sync fences have 
  been signaled by the HAL. The framework will not submit new requests for capture 
  while the configure_streams() call is underway.</p>
<h4><strong>Postconditions</strong></h4>
<p>The HAL device must configure itself to provide maximum possible output frame 
  rate given the sizes and formats of the output streams, as documented in the 
  camera device's static metadata.</p>
<h4><strong>Performance expectations</strong></h4>
<p>This call is expected to be heavyweight and possibly take several hundred 
  milliseconds to complete, since it may require resetting and reconfiguring the 
  image sensor and the camera processing pipeline. Nevertheless, the HAL device 
  should attempt to minimize the reconfiguration delay to minimize the 
  user-visible pauses during application operational mode changes (such as 
  switching from still capture to video recording).</p>
<h4><strong>Return values</strong></h4>
<ul>
  <li>0: On successful stream configuration</li>
  <li>undefined</li>
  <li>-EINVAL: If the requested stream configuration is invalid. Some examples of 
    invalid stream configurations include:
    <ul>
      <li>Including more than 1 input-capable stream (INPUT or BIDIRECTIONAL)</li>
      <li>Not including any output-capable streams (OUTPUT or BIDIRECTIONAL)</li>
      <li>Including streams with unsupported formats, or an unsupported size for 
        that format.</li>
      <li>Including too many output streams of a certain format.</li>
      <li>Note that the framework submitting an invalid stream configuration is not 
        normal operation, since stream configurations are checked before 
        configure. An invalid configuration means that a bug exists in the 
        framework code, or there is a mismatch between the HAL's static metadata 
        and the requirements on streams.</li>
    </ul>
  </li>
  <li>-ENODEV: If there has been a fatal error and the device is no longer 
    operational. Only close() can be called successfully by the framework after 
    this error is returned.</li>
</ul>
<h3 id="register-stream">register_stream_buffers</h3>
<p>Register buffers for a given stream with the HAL device. This method is called 
  by the framework after a new stream is defined by configure_streams, and before 
  buffers from that stream are included in a capture request. If the same stream 
  is listed in a subsequent configure_streams() call, register_stream_buffers will 
  not be called again for that stream.<br/>
  The framework does not need to register buffers for all configured streams 
  before it submits the first capture request. This allows quick startup for 
  preview (or similar use cases) while other streams are still being allocated.<br/>
  This method is intended to allow the HAL device to map or otherwise prepare the 
  buffers for later use. The buffers passed in will already be locked for use. At 
  the end of the call, all the buffers must be ready to be returned to the stream. 
  The bufferset argument is only valid for the duration of this call.<br/>
  If the stream format was set to HAL_PIXEL_FORMAT_IMPLEMENTATION_DEFINED, the 
  camera HAL should inspect the passed-in buffers here to determine any 
  platform-private pixel format information.</p>
<h4><strong>Return values</strong></h4>
<ul>
  <li>0: On successful registration of the new stream buffers</li>
  <li>-EINVAL: If the streambufferset does not refer to a valid active stream, or 
    if the buffers array is invalid.</li>
  <li>-ENOMEM: If there was a failure in registering the buffers. The framework must 
    consider all the stream buffers to be unregistered, and can try to register 
    again later.</li>
  <li>-ENODEV: If there is a fatal error, and the device is no longer operational. 
    Only close() can be called successfully by the framework after this error is 
    returned.</li>
</ul>