The beginnings of a new parameter system.

apps/systemlib/param/param.h

@@ -0,0 +1,140 @@
+/**
+ * @file param.h
+ *
+ * Global parameter store.
+ */
+
+#ifndef _SYSTEMLIB_PARAM_PARAM_H
+#define _SYSTEMLIB_PARAM_PARAM_H
+
+#include <stdint.h>
+
+/**
+ * Parameter types.
+ */
+typedef enum param_type_e
+{
+	/* globally-known parameter types */
+	PARAM_TYPE_INT32 = 0,
+	PARAM_TYPE_FLOAT,
+
+	/* structure parameters; these are expected to be identified by name */
+	PARAM_TYPE_STRUCT = 100,
+	PARAM_TYPE_STRUCT_MAX = 16384 + PARAM_TYPE_STRUCT,
+
+	PARAM_TYPE_UNKNOWN = 0xffff
+} param_type_t;
+
+/**
+ * Parameter handle.
+ *
+ * Parameters are represented by parameter handles, which can
+ * be obtained by looking up (or creating?) parameters.
+ */
+typedef uintptr_t	param_t;
+
+/**
+ * Handle returned when a parameter cannot be found.
+ */
+#define PARAM_INVALID	((uintptr_t)0xffffffff)
+
+/**
+ * Look up a parameter by name.
+ *
+ * @param name		The canonical name of the parameter being looked up.
+ * @return		A handle to the parameter, or PARAM_INVALID if the parameter does not exist.
+ */
+__EXPORT param_t	param_find(const char *name);
+
+/**
+ * Obtain the type of a parameter.
+ *
+ * @param param		A handle returned by param_find.
+ * @return		The type assigned to the parameter.
+ */
+__EXPORT param_type_t	param_type(param_t param);
+
+/**
+ * Determine the size of a parameter.
+ *
+ * @param param		A handle returned by param_find.
+ * @return		The size of the parameter's value.
+ */
+__EXPORT size_t		param_size(param_t param);
+
+/**
+ * Obtain the scalar value of a parameter.
+ *
+ * @param param		A handle returned by param_find.
+ * @param val		Where to return the value, assumed to point to suitable storage for the parameter type.
+ *			For structures, a pointer to the structure is returned.
+ * @return		Zero if the parameter's value could be returned as a scalar, nonzero otherwise.
+ */
+__EXPORT int		param_get(param_t param, void *val);
+
+/**
+ * Set the scalar value of a parameter.
+ *
+ * @param param		A handle returned by param_find.
+ * @param val		The value to set; assumed to point to a variable of the parameter type.
+ *			For structures, the pointer is assumed to point to a copy of the structure.
+ * @return		Zero if the parameter's value could be set from a scalar, nonzero otherwise.
+ */
+__EXPORT int		param_set(param_t param, void *val);
+
+/*
+ * Macros creating static parameter definitions.
+ *
+ * Note that these structures are not known by name; they are 
+ * collected into a section that is iterated by the parameter
+ * code.
+ */
+
+/** define an int32 parameter */
+#define PARAM_DEFINE_INT32(_name, _default)		\
+	static const					\
+	__attribute__((used, section("__param")))	\
+	struct param_info_s __param__##_name = {	\
+		.name = #_name,				\
+		.type = PARAM_TYPE_INT32,		\
+		.i = _default				\
+	}
+
+/** define a float parameter */
+#define PARAM_DEFINE_FLOAT(_name, _default)		\
+	static const					\
+	__attribute__((used, section("__param")))	\
+	struct param_info_s __param__##_name = {	\
+		.name = #_name,				\
+		.type = PARAM_TYPE_FLOAT,		\
+		.f = _default				\
+	}
+
+/** define a parameter that points to a structure */
+#define PARAM_DEFINE_STRUCT(_name, _default)		\
+	static const					\
+	__attribute__((used, section("__param")))	\
+	struct param_info_s __param__##_name = {	\
+		.name = #_name,				\
+		.type = PARAM_TYPE_STRUCT + sizeof(_default), \
+		.p = &_default;				\
+	}
+
+/**
+ * Static parameter definition structure.
+ *
+ * This is normally not used by user code; see the PARAM_DEFINE macros
+ * instead.
+ */
+struct param_info_s
+{
+	const char	*name;
+	param_type_t	type;
+	union {
+		void		*p;
+		int32_t		i;
+		float		f;
+	};
+};
+
+#endif