ipa: rkisp1: Introduce AGC

Now that we have IPAContext and Algorithm, we can implement a simple AGC
based on the IPU3 one. It is very similar, except that there is no
histogram used for an inter quantile mean. The RkISP1 is returning a 5x5
array (for V10) of luminance means. Estimating the relative luminance is
thus a simple mean of all the blocks already calculated by the ISP.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/ipa/rkisp1/ipa_context.cpp

@@ -56,6 +56,21 @@ namespace libcamera::ipa::rkisp1 {
  */
 
 /**
+ * \var IPASessionConfiguration::agc
+ * \brief AGC parameters configuration of the IPA
+ *
+ * \var IPASessionConfiguration::agc.minShutterSpeed
+ * \brief Minimum shutter speed supported with the configured sensor
+ *
+ * \var IPASessionConfiguration::agc.maxShutterSpeed
+ * \brief Maximum shutter speed supported with the configured sensor
+ *
+ * \var IPASessionConfiguration::agc.minAnalogueGain
+ * \brief Minimum analogue gain supported with the configured sensor
+ *
+ * \var IPASessionConfiguration::agc.maxAnalogueGain
+ * \brief Maximum analogue gain supported with the configured sensor
+ *
  * \var IPASessionConfiguration::hw
  * \brief RkISP1-specific hardware information
  *
@@ -63,4 +78,39 @@ namespace libcamera::ipa::rkisp1 {
  * \brief Hardware revision of the ISP
  */
 
+/**
+ * \var IPASessionConfiguration::sensor
+ * \brief Sensor-specific configuration of the IPA
+ *
+ * \var IPASessionConfiguration::sensor.lineDuration
+ * \brief Line duration in microseconds
+ */
+
+/**
+ * \var IPAFrameContext::agc
+ * \brief Context for the Automatic Gain Control algorithm
+ *
+ * The exposure and gain determined are expected to be applied to the sensor
+ * at the earliest opportunity.
+ *
+ * \var IPAFrameContext::agc.exposure
+ * \brief Exposure time expressed as a number of lines
+ *
+ * \var IPAFrameContext::agc.gain
+ * \brief Analogue gain multiplier
+ *
+ * The gain should be adapted to the sensor specific gain code before applying.
+ */
+
+/**
+ * \var IPAFrameContext::sensor
+ * \brief Effective sensor values
+ *
+ * \var IPAFrameContext::sensor.exposure
+ * \brief Exposure time expressed as a number of lines
+ *
+ * \var IPAFrameContext::sensor.gain
+ * \brief Analogue gain multiplier
+ */
+
 } /* namespace libcamera::ipa::rkisp1 */