target: provide container_of()

Provide a cleaner way to handle single inheritance of targets
in C, using the same model Linux does:  structs containing other
structs, un-nested via calls to a "container_of()" macro that
are packaged in typesafe inline functions.

Targets already use this containment idiom, but make it much
more complicated because they un-nest using embedded "void *"
pointers ... in chains of up to five per target, which is all
pure needless complication.  (Example: arm92x core, arm9tdmi,
arm7_9, armv4_5 ... on top of the base "target" class.)

Applying this scheme consistently simplifies things, and gets
rid of many error-prone untyped pointers.  It won't change any
part of the type model though -- it just simplifies things.
(And facilitates more cleanup later on.)

Rule of thumb:  where there's an X->arch_info void* pointer,
access to that pointer can and should be removed.  It may be
convenient to set up pointers to some of the embedded structs;
and shrink their current "*_common" names (annoyingly long).

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>

src/target/arm720t.h

@@ -35,4 +35,11 @@ typedef struct arm720t_common_s
 	uint32_t far_reg;
 } arm720t_common_t;
 
+static inline struct arm720t_common_s *
+target_to_arm720(struct target_s *target)
+{
+	return container_of(target->arch_info, struct arm720t_common_s,
+			arm7tdmi_common.arm7_9_common.armv4_5_common);
+}
+
 #endif /* ARM720T_H */

src/target/arm7_9_common.h

@@ -112,6 +112,13 @@ typedef struct arm7_9_common_s
 
 } arm7_9_common_t;
 
+static inline struct arm7_9_common_s *
+target_to_arm7_9(struct target_s *target)
+{
+	return container_of(target->arch_info, struct arm7_9_common_s,
+			armv4_5_common);
+}
+
 int arm7_9_register_commands(struct command_context_s *cmd_ctx);
 
 int arm7_9_poll(target_t *target);

src/target/arm920t.h

@@ -38,6 +38,13 @@ typedef struct arm920t_common_s
 	int preserve_cache;
 } arm920t_common_t;
 
+static inline struct arm920t_common_s *
+target_to_arm920(struct target_s *target)
+{
+	return container_of(target->arch_info, struct arm920t_common_s,
+			arm9tdmi_common.arm7_9_common.armv4_5_common);
+}
+
 typedef struct arm920t_cache_line_s
 {
 	uint32_t cam;

src/target/arm926ejs.h

@@ -38,6 +38,14 @@ typedef struct arm926ejs_common_s
 	uint32_t d_far;
 } arm926ejs_common_t;
 
+static inline struct arm926ejs_common_s *
+target_to_arm926(struct target_s *target)
+{
+	return container_of(target->arch_info, struct arm926ejs_common_s,
+		arm9tdmi_common.arm7_9_common.armv4_5_common);
+}
+
+
 extern int arm926ejs_init_arch_info(target_t *target, arm926ejs_common_t *arm926ejs, jtag_tap_t *tap);
 extern int arm926ejs_register_commands(struct command_context_s *cmd_ctx);
 extern int arm926ejs_arch_state(struct target_s *target);

src/target/arm966e.h

@@ -34,6 +34,13 @@ typedef struct arm966e_common_s
 	uint32_t cp15_control_reg;
 } arm966e_common_t;
 
+static inline struct arm966e_common_s *
+target_to_arm966(struct target_s *target)
+{
+	return container_of(target->arch_info, struct arm966e_common_s,
+			arm9tdmi_common.arm7_9_common.armv4_5_common);
+}
+
 extern int arm966e_init_arch_info(target_t *target, arm966e_common_t *arm966e, jtag_tap_t *tap);
 extern int arm966e_register_commands(struct command_context_s *cmd_ctx);
 extern int arm966e_write_cp15(target_t *target, int reg_addr, uint32_t value);

src/target/armv4_5.h

@@ -86,6 +86,12 @@ typedef struct armv4_5_common_s
 	void *arch_info;
 } armv4_5_common_t;
 
+static inline struct armv4_5_common_s *
+target_to_armv4_5(struct target_s *target)
+{
+	return target->arch_info;
+}
+
 typedef struct armv4_5_algorithm_s
 {
 	int common_magic;

src/target/armv7a.h

@@ -127,6 +127,13 @@ typedef struct armv7a_common_s
 
 } armv7a_common_t;
 
+static inline struct armv7a_common_s *
+target_to_armv7a(struct target_s *target)
+{
+	return container_of(target->arch_info, struct armv7a_common_s,
+			armv4_5_common);
+}
+
 typedef struct armv7a_algorithm_s
 {
 	int common_magic;

src/target/armv7m.h

@@ -116,6 +116,12 @@ typedef struct armv7m_common_s
 	void *arch_info;
 } armv7m_common_t;
 
+static inline struct armv7m_common_s *
+target_to_armv7m(struct target_s *target)
+{
+	return target->arch_info;
+}
+
 typedef struct armv7m_algorithm_s
 {
 	int common_magic;

src/target/cortex_a8.h

@@ -137,6 +137,13 @@ typedef struct cortex_a8_common_s
 	void *arch_info;
 } cortex_a8_common_t;
 
+static inline struct cortex_a8_common_s *
+target_to_cortex_a8(struct target_s *target)
+{
+	return container_of(target->arch_info, struct cortex_a8_common_s,
+			armv7a_common.armv4_5_common);
+}
+
 extern int cortex_a8_init_arch_info(target_t *target, cortex_a8_common_t *cortex_a8, jtag_tap_t *tap);
 int cortex_a8_read_memory(struct target_s *target, uint32_t address, uint32_t size, uint32_t count, uint8_t *buffer);
 int cortex_a8_write_memory(struct target_s *target, uint32_t address, uint32_t size, uint32_t count, uint8_t *buffer);

src/target/cortex_m3.h

@@ -164,4 +164,11 @@ typedef struct cortex_m3_common_s
 	void *arch_info;
 } cortex_m3_common_t;
 
+static inline struct cortex_m3_common_s *
+target_to_cm3(struct target_s *target)
+{
+	return container_of(target->arch_info,
+			struct cortex_m3_common_s, armv7m);
+}
+
 #endif /* CORTEX_M3_H */

src/target/target.h

@@ -26,6 +26,8 @@
 #ifndef TARGET_H
 #define TARGET_H
 
+#include <stddef.h>
+
 #include "breakpoints.h"
 #include "algorithm.h"
 #include "command.h"
@@ -34,6 +36,19 @@ struct reg_s;
 struct trace_s;
 struct command_context_s;
 
+
+/**
+ * Cast a member of a structure out to the containing structure.
+ * @param ptr The pointer to the member.
+ * @param type The type of the container struct this is embedded in.
+ * @param member The name of the member within the struct.
+ *
+ * This is a mechanism which is used throughout the Linux kernel.
+ */
+#define container_of(ptr, type, member) ({			\
+	const typeof( ((type *)0)->member ) *__mptr = (ptr);	\
+	(type *)( (char *)__mptr - offsetof(type,member) );})
+
 /*
  * TARGET_UNKNOWN = 0: we don't know anything about the target yet
  * TARGET_RUNNING = 1: the target is executing user code

src/target/xscale.h

@@ -134,6 +134,13 @@ typedef struct xscale_common_s
 	int fast_memory_access;
 } xscale_common_t;
 
+static inline struct xscale_common_s *
+target_to_xscale(struct target_s *target)
+{
+	return container_of(target->arch_info, struct xscale_common_s,
+			armv4_5_common);
+}
+
 typedef struct xscale_reg_s
 {
 	int dbg_handler_number;