libcamera: controls: Add support for string controls

String controls are stored internally as an array of char, but the
ControlValue constructor, get() and set() functions operate on an
std::string for convenience. Array of strings are thus not supported.

Unlike for other control types, the ControlInfo range reports the
minimum and maximum allowed lengths of the string (the minimum will
usually be 0), not the minimum and maximum value of each element.

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

1 files changed, 22 insertions, 0 deletions

diff --git a/src/libcamera/control_serializer.cpp b/src/libcamera/control_serializer.cpp
index eef875f4..808419f2 100644
--- a/src/libcamera/control_serializer.cpp
+++ b/src/libcamera/control_serializer.cpp
@@ -314,6 +314,22 @@ ControlValue ControlSerializer::loadControlValue(ByteStreamBuffer &buffer,
 	return value;
 }
 
+template<>
+ControlValue ControlSerializer::loadControlValue<std::string>(ByteStreamBuffer &buffer,
+						 bool isArray,
+						 unsigned int count)
+{
+	ControlValue value;
+
+	const char *data = buffer.read<char>(count);
+	if (!data)
+		return value;
+
+	value.set(std::string{ data, count });
+
+	return value;
+}
+
 ControlValue ControlSerializer::loadControlValue(ControlType type,
 						 ByteStreamBuffer &buffer,
 						 bool isArray,
@@ -335,6 +351,9 @@ ControlValue ControlSerializer::loadControlValue(ControlType type,
 	case ControlTypeFloat:
 		return loadControlValue<float>(buffer, isArray, count);
 
+	case ControlTypeString:
+		return loadControlValue<std::string>(buffer, isArray, count);
+
 	case ControlTypeNone:
 		return ControlValue();
 	}
@@ -345,6 +364,9 @@ ControlValue ControlSerializer::loadControlValue(ControlType type,
 ControlInfo ControlSerializer::loadControlInfo(ControlType type,
 					       ByteStreamBuffer &b)
 {
+	if (type == ControlTypeString)
+		type = ControlTypeInteger32;
+
 	ControlValue min = loadControlValue(type, b);
 	ControlValue max = loadControlValue(type, b);