libcamera: controls: Generate and use fixed-sized Span types

Define Span types explicitly as either variable- or fixed-sized. This
introduces a new convention for defining Span dimensions in the property
and control value definitions and generates Span types as variable-sized
Span<T> or as fixed-sized Span<T,N>.

Signed-off-by: Christian Rauch <Rauch.Christian@gmx.de>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

include/libcamera/controls.h

@@ -168,7 +168,7 @@ public:
 
 		using V = typename T::value_type;
 		const V *value = reinterpret_cast<const V *>(data().data());
-		return { value, numElements_ };
+		return T{ value, numElements_ };
 	}
 
 #ifndef __DOXYGEN__

src/ipa/raspberrypi/raspberrypi.cpp

@@ -567,18 +567,19 @@ void IPARPi::reportMetadata()
 
 	AwbStatus *awbStatus = rpiMetadata_.getLocked<AwbStatus>("awb.status");
 	if (awbStatus) {
-		libcameraMetadata_.set(controls::ColourGains, { static_cast<float>(awbStatus->gainR),
-								static_cast<float>(awbStatus->gainB) });
+		libcameraMetadata_.set(controls::ColourGains,
+				       Span<const float, 2>({ static_cast<float>(awbStatus->gainR),
+							      static_cast<float>(awbStatus->gainB) }));
 		libcameraMetadata_.set(controls::ColourTemperature, awbStatus->temperatureK);
 	}
 
 	BlackLevelStatus *blackLevelStatus = rpiMetadata_.getLocked<BlackLevelStatus>("black_level.status");
 	if (blackLevelStatus)
 		libcameraMetadata_.set(controls::SensorBlackLevels,
-				       { static_cast<int32_t>(blackLevelStatus->blackLevelR),
-					 static_cast<int32_t>(blackLevelStatus->blackLevelG),
-					 static_cast<int32_t>(blackLevelStatus->blackLevelG),
-					 static_cast<int32_t>(blackLevelStatus->blackLevelB) });
+				       Span<const int32_t, 4>({ static_cast<int32_t>(blackLevelStatus->blackLevelR),
+								static_cast<int32_t>(blackLevelStatus->blackLevelG),
+								static_cast<int32_t>(blackLevelStatus->blackLevelG),
+								static_cast<int32_t>(blackLevelStatus->blackLevelB) }));
 
 	FocusStatus *focusStatus = rpiMetadata_.getLocked<FocusStatus>("focus.status");
 	if (focusStatus && focusStatus->num == 12) {
@@ -883,7 +884,7 @@ void IPARPi::queueRequest(const ControlList &controls)
 			if (gains[0] != 0.0f && gains[1] != 0.0f)
 				/* A gain of 0.0f will switch back to auto mode. */
 				libcameraMetadata_.set(controls::ColourGains,
-						       { gains[0], gains[1] });
+						       Span<const float, 2>({ gains[0], gains[1] }));
 			break;
 		}
 
@@ -1167,8 +1168,8 @@ void IPARPi::applyFrameDurations(Duration minFrameDuration, Duration maxFrameDur
 
 	/* Return the validated limits via metadata. */
 	libcameraMetadata_.set(controls::FrameDurationLimits,
-			       { static_cast<int64_t>(minFrameDuration_.get<std::micro>()),
-				 static_cast<int64_t>(maxFrameDuration_.get<std::micro>()) });
+			       Span<const int64_t, 2>({ static_cast<int64_t>(minFrameDuration_.get<std::micro>()),
+							static_cast<int64_t>(maxFrameDuration_.get<std::micro>()) }));
 
 	/*
 	 * Calculate the maximum exposure time possible for the AGC to use.

src/libcamera/control_ids.yaml

@@ -291,7 +291,7 @@ controls:
         transformation. The 3x3 matrix is stored in conventional reading
         order in an array of 9 floating point values.
 
-      size: [3x3]
+      size: [3,3]
 
   - ScalerCrop:
       type: Rectangle
@@ -525,7 +525,7 @@ controls:
         the window where the focal distance for the objects shown in that part
         of the image are closest to the camera.
 
-      size: [n]
+      size: []
 
   - AfTrigger:
       type: int32_t

src/libcamera/property_ids.yaml

@@ -497,7 +497,7 @@ controls:
 
   - PixelArrayOpticalBlackRectangles:
       type: Rectangle
-      size: [n]
+      size: []
       description: |
         The pixel array region(s) which contain optical black pixels
         considered valid for calibration purposes.
@@ -592,7 +592,7 @@ controls:
 
   - PixelArrayActiveAreas:
       type: Rectangle
-      size: [n]
+      size: []
       description: |
         The PixelArrayActiveAreas property defines the (possibly multiple and
         overlapping) portions of the camera sensor readable pixel matrix

src/qcam/dng_writer.cpp

@@ -517,7 +517,7 @@ int DNGWriter::write(const char *filename, const Camera *camera,
 
 	const auto &blackLevels = metadata.get(controls::SensorBlackLevels);
 	if (blackLevels) {
-		Span<const int32_t> levels = *blackLevels;
+		Span<const int32_t, 4> levels = *blackLevels;
 
 		/*
 		 * The black levels control is specified in R, Gr, Gb, B order.

utils/gen-controls.py

@@ -7,6 +7,8 @@
 # gen-controls.py - Generate control definitions from YAML
 
 import argparse
+from functools import reduce
+import operator
 import string
 import sys
 import yaml
@@ -22,6 +24,24 @@ def format_description(description):
     return '\n'.join([(line and ' * ' or ' *') + line for line in description])
 
 
+def get_ctrl_type(ctrl):
+    ctrl_type = ctrl['type']
+    ctrl_size_arr = ctrl.get('size')
+
+    if ctrl_type == 'string':
+        return 'std::string'
+    elif ctrl_size_arr is not None:
+        if len(ctrl_size_arr) > 0:
+            # fixed-sized Span
+            ctrl_span_size = reduce(operator.mul, ctrl_size_arr)
+            return f"Span<const {ctrl_type}, {ctrl_span_size}>"
+        else:
+            # variable-sized Span
+            return f"Span<const {ctrl_type}>"
+    else:
+        return ctrl_type
+
+
 def generate_cpp(controls):
     enum_doc_start_template = string.Template('''/**
  * \\enum ${name}Enum
@@ -50,11 +70,7 @@ ${description}
         name, ctrl = ctrl.popitem()
         id_name = snake_case(name).upper()
 
-        ctrl_type = ctrl['type']
-        if ctrl_type == 'string':
-            ctrl_type = 'std::string'
-        elif ctrl.get('size'):
-            ctrl_type = 'Span<const %s>' % ctrl_type
+        ctrl_type = get_ctrl_type(ctrl)
 
         info = {
             'name': name,
@@ -135,11 +151,7 @@ def generate_h(controls):
 
         ids.append('\t' + id_name + ' = ' + str(id_value) + ',')
 
-        ctrl_type = ctrl['type']
-        if ctrl_type == 'string':
-            ctrl_type = 'std::string'
-        elif ctrl.get('size'):
-            ctrl_type = 'Span<const %s>' % ctrl_type
+        ctrl_type = get_ctrl_type(ctrl)
 
         info = {
             'name': name,