Support for autonomous actions

Essential part of the utility is to handle input data and optionally
interact with hardware to fetch this data. So the utility have an
advaced common interface for data fetching (connectors) and connector
configuration is always mandatory. This is due to the fact that
connector descriptor accessed via pointer in many places without
checking it for validity.

But sometime we need an autonomous (self-contained) action that do not
interacts with outer word, e.d. do not access hardware, do not read
input dumps, etc. Require the user to specify a connector (see above),
that will be in fact ignored is senseless. Reworking whole code and
check connector pointer each time before the access is not an option.

So, add a special action flag that indicates that a particular
action is autonomous. If the user has not specified a connector
invoking such an autonomous action, then silently setup a special
'stub' connector. This 'stub' connector actually do nothing and its
purpose to make init and exit handlers invocation safe without rewriting
a lot of code.

Author: rsa9000

Makefile

@@ -4,6 +4,7 @@ TARGET=atheepmgr
 OBJ=\
 	atheepmgr.o	\
 	con_file.o	\
+	con_stub.o	\
 	eep_5211.o	\
 	eep_5416.o	\
 	eep_9285.o	\

atheepmgr.c

@@ -398,6 +398,7 @@ static int act_reg_write(struct atheepmgr *aem, int argc, char *argv[])
 
 #define ACT_F_DATA	(1 << 0)	/* Action will interact with EEPROM/OTP data */
 #define ACT_F_HW	(1 << 1)	/* Action require direct HW access */
+#define ACT_F_AUTONOMOUS (1 << 2)	/* Action do not require input data or HW */
 
 static const struct action {
 	const char *name;
@@ -657,11 +658,6 @@ int main(int argc, char *argv[])
 		}
 	}
 
-	if (!aem->con) {
-		fprintf(stderr, "Connector is not specified\n");
-		goto exit;
-	}
-
 	if (optind >= argc) {
 		act = &actions[0];
 	} else {
@@ -678,6 +674,15 @@ int main(int argc, char *argv[])
 		optind++;
 	}
 
+	if (!aem->con) {
+		if (act->flags & ACT_F_AUTONOMOUS) {
+			aem->con = &con_stub;	/* to avoid conn. init crash */
+		} else {
+			fprintf(stderr, "Connector is not specified\n");
+			goto exit;
+		}
+	}
+
 	if ((act->flags & ACT_F_HW) && !(aem->con->caps & CON_CAP_HW)) {
 		fprintf(stderr, "%s action require direct HW access, which is not proved by %s connector\n",
 			act->name, aem->con->name);

atheepmgr.h

@@ -256,6 +256,7 @@ struct atheepmgr {
 extern const struct connector con_file;
 extern const struct connector con_mem;
 extern const struct connector con_pci;
+extern const struct connector con_stub;
 
 extern const struct eepmap eepmap_5211;
 extern const struct eepmap eepmap_5416;

con_stub.c

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2020 Sergey Ryazanov <[email protected]>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "atheepmgr.h"
+
+static int stub_init(struct atheepmgr *aem, const char *arg)
+{
+	return 0;
+}
+
+static void stub_clean(struct atheepmgr *aem)
+{
+}
+
+const struct connector con_stub = {
+	.name = "Stub",
+	.init = stub_init,
+	.clean = stub_clean,
+};