utils: gen-controls: Improve YAML notation for variable-size array controls

Array controls specify the array size through the YAML 'size' element,
which stores a list of values, one per dimension. Variable-size arrays
currently use an empty 'size' list, which prevents describing the number
of dimensions of the array.

Improve this by using the same notation for fixed-size and variable-size
array controls. Dimensions that are not fixed are described as a string
instead of an integer, such as [n], [n,3] or [w,h]. The strings have
currently no special meaning, this may change in the future.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>

src/libcamera/control_ids.yaml

@@ -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: []
+      size: [n]
 
   - AfTrigger:
       type: int32_t

src/libcamera/property_ids.yaml

@@ -497,7 +497,7 @@ controls:
 
   - PixelArrayOpticalBlackRectangles:
       type: Rectangle
-      size: []
+      size: [n]
       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: []
+      size: [n]
       description: |
         The PixelArrayActiveAreas property defines the (possibly multiple and
         overlapping) portions of the camera sensor readable pixel matrix

utils/gen-controls.py

@@ -39,11 +39,33 @@ class Control(object):
         self.__name = name
         self.__data = data
         self.__enum_values = None
+        self.__size = None
 
         enum_values = data.get('enum')
         if enum_values is not None:
             self.__enum_values = [ControlEnum(enum) for enum in enum_values]
 
+        size = self.__data.get('size')
+        if size is not None:
+            if len(size) == 0:
+                raise RuntimeError(f'Control `{self.__name}` size must have at least one dimension')
+
+            # Compute the total number of elements in the array. If any of the
+            # array dimension is a string, the array is variable-sized.
+            num_elems = 1
+            for dim in size:
+                if type(dim) is str:
+                    num_elems = 0
+                    break
+
+                dim = int(dim)
+                if dim <= 0:
+                    raise RuntimeError(f'Control `{self.__name}` size must have positive values only')
+
+                num_elems *= dim
+
+            self.__size = num_elems
+
     @property
     def description(self):
         """The control description"""
@@ -86,15 +108,12 @@ class Control(object):
         if typ == 'string':
             return 'std::string'
 
-        if size is None:
+        if self.__size is None:
             return typ
 
-        if len(size) > 0:
+        if self.__size:
-            # fixed-sized Span
+            return f"Span<const {typ}, {self.__size}>"
-            span_size = reduce(operator.mul, size)
-            return f"Span<const {typ}, {span_size}>"
         else:
-            # variable-sized Span
             return f"Span<const {typ}>"