transport selection tweaks

* Bugfix and simplify legacy jtag-only defaulting
* Make "dummy" declare its jtag-only nature
* likewise update ft2232
* warn if selection is _required_ (multi-transport adapters),

fixes the "only ft2232 works" bug for at least dummy, with
other drivers going the "legacy" path (submit patches).

Signed-off-by: David Brownell <db@helium.(none)>

src/jtag/adapter.c

@@ -93,6 +93,9 @@ static int default_srst_asserted(int *srst_asserted)
 	return ERROR_OK;
 }
 
+const char *jtag_only[] = { "jtag", NULL, };
+
+
 COMMAND_HANDLER(interface_transport_command)
 {
 	char **transports;
@@ -130,6 +133,8 @@ COMMAND_HANDLER(handle_interface_list_command)
 
 COMMAND_HANDLER(handle_interface_command)
 {
+	int retval;
+
 	/* check whether the interface is already configured */
 	if (jtag_interface)
 	{
@@ -148,7 +153,7 @@ COMMAND_HANDLER(handle_interface_command)
 
 		if (NULL != jtag_interfaces[i]->commands)
 		{
-			int retval = register_commands(CMD_CTX, NULL,
+			retval = register_commands(CMD_CTX, NULL,
 					jtag_interfaces[i]->commands);
 			if (ERROR_OK != retval)
 				return retval;
@@ -156,6 +161,20 @@ COMMAND_HANDLER(handle_interface_command)
 
 		jtag_interface = jtag_interfaces[i];
 
+	/* LEGACY SUPPORT ... adapter drivers  must declare what
+	 * transports they allow.  Until they all do so, assume
+	 * the legacy drivers are JTAG-only
+	 */
+	if (!jtag_interface->transports)
+		LOG_WARNING("Adapter driver '%s' did not declare "
+			"which transports it allows; assuming"
+			"legacy JTAG-only", jtag_interface->name);
+		retval = allow_transports(CMD_CTX,
+					jtag_interface->transports
+						? : jtag_only);
+			if (ERROR_OK != retval)
+				return retval;
+
 		if (jtag_interface->khz == NULL)
 			jtag_interface->khz = default_khz;
 		if (jtag_interface->speed_div == NULL)
@@ -171,7 +190,8 @@ COMMAND_HANDLER(handle_interface_command)
 	/* no valid interface was found (i.e. the configuration option,
 	 * didn't match one of the compiled-in interfaces
 	 */
-	LOG_ERROR("The specified debug interface was not found (%s)", CMD_ARGV[0]);
+	LOG_ERROR("The specified debug interface was not found (%s)",
+				CMD_ARGV[0]);
 	CALL_COMMAND_HANDLER(handle_interface_list_command);
 	return ERROR_JTAG_INVALID_INTERFACE;
 }

src/jtag/drivers/dummy.c

@@ -166,6 +166,7 @@ struct jtag_interface dummy_interface = {
 
 		.supported = DEBUG_CAP_TMS_SEQ,
 		.commands = dummy_command_handlers,
+		.transports = jtag_only,
 
 		.execute_queue = &bitbang_execute_queue,
 

src/jtag/drivers/ft2232.c

@@ -168,7 +168,6 @@ struct ft2232_layout {
 	void (*reset)(int trst, int srst);
 	void (*blink)(void);
 	int channel;
-	const char **transports;
 };
 
 /* init procedures for supported layouts */
@@ -213,11 +212,8 @@ static void signalyzer_h_blink(void);
 static void ktlink_blink(void);
 
 /* common transport support options */
-static const char *jtag_only[] = { "jtag", NULL };
-
 
 //static const char *jtag_and_swd[] = { "jtag", "swd", NULL };
-#define jtag_and_swd NULL
 
 static const struct ft2232_layout  ft2232_layouts[] =
 {
@@ -244,12 +240,10 @@ static const struct ft2232_layout  ft2232_layouts[] =
 	{ .name = "evb_lm3s811",
 		.init = lm3s811_jtag_init,
 		.reset = ftx23_reset,
-		.transports = jtag_and_swd,
 	},
 	{ .name = "luminary_icdi",
 		.init = icdi_jtag_init,
 		.reset = ftx23_reset,
-		.transports = jtag_and_swd,
 	},
 	{ .name = "olimex-jtag",
 		.init = olimex_jtag_init,
@@ -3206,11 +3200,7 @@ COMMAND_HANDLER(ft2232_handle_layout_command)
 	for (const struct ft2232_layout *l = ft2232_layouts; l->name; l++) {
 		if (strcmp(l->name, CMD_ARGV[0]) == 0) {
 			layout = l;
-			/* This may also select the transport
-			 * if we only support one of them.
-			 */
-			return allow_transports(CMD_CTX,
-				l->transports ? : jtag_only);
+			return ERROR_OK;
 		}
 	}
 
@@ -4372,6 +4362,7 @@ struct jtag_interface ft2232_interface = {
 	.name = "ft2232",
 	.supported = DEBUG_CAP_TMS_SEQ,
 	.commands = ft2232_command_handlers,
+	.transports = jtag_only,
 
 	.init = ft2232_init,
 	.quit = ft2232_quit,

src/jtag/interface.h

@@ -206,6 +206,9 @@ struct jtag_interface {
 	unsigned supported;
 #define DEBUG_CAP_TMS_SEQ	(1 << 0)
 
+	/** transports supported in C code (NULL terminated vector) */
+	const char **transports;
+
 	/**
 	 * Execute queued commands.
 	 * @returns ERROR_OK on success, or an error code on failure.
@@ -289,4 +292,6 @@ struct jtag_interface {
 };
 
 
+extern const char *jtag_only[];
+
 #endif // OPENOCD_JTAG_INTERFACE_H

src/jtag/transport.c

@@ -101,6 +101,10 @@ int allow_transports(struct command_context *ctx, const char **vector)
 	 *
 	 * REVISIT should we validate that?  and insist there's
 	 * at least one non-NULL element in that list?
+	 *
+	 * ... allow removals, e.g. external strapping prevents use
+	 * of one transport; C code should be definitive about what
+	 * can be used when all goes well.
 	 */
 	if (allowed_transports != NULL || session) {
 		LOG_ERROR("Can't modify the set of allowed transports.");
@@ -116,6 +120,8 @@ int allow_transports(struct command_context *ctx, const char **vector)
 				vector[0]);
 		return transport_select(ctx, vector [0]);
 	} else {
+		/* guard against user config errors */
+		LOG_WARNING("must select a transport.");
 		while (*vector)
 			LOG_DEBUG("allow transport '%s'", *vector++);
 		return ERROR_OK;
@@ -304,13 +310,14 @@ COMMAND_HANDLER(handle_transport_select)
 	/* Is this transport supported by our debug adapter?
 	 * Example, "JTAG-only" means SWD is not supported.
 	 *
-	 * NOTE:  requires adapter to have been set up, including
-	 * declaring transport via C code or Tcl script.
+	 * NOTE:  requires adapter to have been set up, with
+	 * transports declared via C.
 	 */
 	if (!allowed_transports) {
 		LOG_ERROR("Debug adapter doesn't support any transports?");
 		return ERROR_FAIL;
 	}
+
 	for (unsigned i = 0; allowed_transports[i]; i++) {
 
 		if (strcmp(allowed_transports[i], CMD_ARGV[0]) == 0)