libcamera: ipa: Pass a set of controls and return results from ipa::start()

This change allows controls passed into PipelineHandler::start to be
forwarded onto IPAInterface::start(). We also add a return channel if the
pipeline handler must action any of these controls, e.g. setting the
analogue gain or shutter speed in the sensor device.

The IPA interface wrapper isn't addressed as it will soon be replaced by
a new mechanism to handle IPC.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: David Plowman <david.plowman@raspberrypi.com>
Tested-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/libcamera/ipa_interface.cpp b/src/libcamera/ipa_interface.cpp
index 23fc56d7..5be6f787 100644
--- a/src/libcamera/ipa_interface.cpp
+++ b/src/libcamera/ipa_interface.cpp
@@ -536,10 +536,17 @@ namespace libcamera {
 /**
  * \fn IPAInterface::start()
  * \brief Start the IPA
+ * \param[in] data Protocol-specific data for the start operation
+ * \param[out] result Result of the start operation
  *
  * This method informs the IPA module that the camera is about to be started.
  * The IPA module shall prepare any resources it needs to operate.
  *
+ * The \a data and \a result parameters carry custom data passed by the
+ * pipeline handler to the IPA and back. The pipeline handler may set the \a
+ * result parameter to null if the IPA protocol doesn't need to pass a result
+ * back through the start() function.
+ *
  * \return 0 on success or a negative error code otherwise
  */