The beginnings of a new parameter system.

2 files changed, 250 insertions, 0 deletions

diff --git a/apps/systemlib/param/param.c b/apps/systemlib/param/param.c
new file mode 100644
index 000000000..bb82941a0
--- /dev/null
+++ b/apps/systemlib/param/param.c
@@ -0,0 +1,110 @@
+/**
+ * @file param.c
+ *
+ * Global parameter store.
+ */
+
+#include <string.h>
+#include <stdbool.h>
+
+#include <unistd.h>
+
+#include "param.h"
+
+/**
+ * Array of static parameter info.
+ */
+extern char __param_start, __param_end;
+static const struct param_info_s	*param_info_base = (struct param_info_s *)&__param_start;
+static const struct param_info_s	*param_info_limit = (struct param_info_s *)&__param_end;
+#define	param_info_count		((unsigned)(param_info_limit - param_info_base))
+
+static bool
+handle_in_range(param_t handle) 
+{
+	return (handle < param_info_count);
+}
+
+param_t
+param_find(const char *name)
+{
+	param_t param;
+
+	for (param = 0; handle_in_range(param); param++) {
+		if (!strcmp(param_info_base[param].name, name))
+			return param;
+	}
+
+	/* not found */
+	return PARAM_INVALID;
+}
+
+enum
+param_type_e param_type(param_t param)
+{
+	if (handle_in_range(param))
+		return param_info_base[param].type;
+
+	return PARAM_TYPE_UNKNOWN;
+}
+
+size_t
+param_size(param_t param)
+{
+
+	if (handle_in_range(param)) {
+		switch (param_info_base[param].type) {
+		case PARAM_TYPE_INT32:
+		case PARAM_TYPE_FLOAT:
+			return 4;
+
+		case PARAM_TYPE_STRUCT ... PARAM_TYPE_STRUCT_MAX:
+			return param_info_base[param].type - PARAM_TYPE_STRUCT;
+
+		default:
+			return 0;
+		}
+	}
+
+	return 0;
+}
+
+int
+param_get(param_t param, void *val)
+{
+	if (handle_in_range(param)) {
+
+		/* XXX look for updated value stored elsewhere */
+
+		switch (param_info_base[param].type) {
+		case PARAM_TYPE_INT32:
+			*(int32_t *)val = param_info_base[param].i;
+			return 0;
+
+		case PARAM_TYPE_FLOAT:
+			*(float *)val = param_info_base[param].f;
+			return 0;
+
+		case PARAM_TYPE_STRUCT ... PARAM_TYPE_STRUCT_MAX:
+			memcpy(val, param_info_base[param].p, param_size(param));
+			return 0;
+
+		default:
+			return -1;
+		}
+	}
+	return -1;
+}
+
+int
+param_set(param_t param, void *val)
+{
+	if (handle_in_range(param)) {
+
+		/* XXX maintain list of changed values */
+
+	}
+	return -1;
+
+}
+
diff --git a/apps/systemlib/param/param.h b/apps/systemlib/param/param.h
new file mode 100644
index 000000000..9f7808f30
--- /dev/null
+++ b/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