formalize log subsys stripping for vty

In osmocom, we historically have a leading 'D' in all of our logging
subsystem names -- not only in the enum entry name, but also as the
string in struct log_info_cat[].

As a result of this, our logging_vty code strips away the first
character of each logging subsystem name. In the VTY, we don't enter
'dmain', but only 'main' -- the VTY strips the 'D' from "DMAIN".

The intention is to make this stripping behavior optional in a
subsequent patch.

So far the code to do that is a magic "+ 1" thrown in here and there.
Instead, introduce log_subsys_name() and use it where ever logging_vty.c
does removal of the leading 'D'.

I would have liked to keep this within logging_vty.c, but unfortunately
it needs to be public API in logging.h, because of log_parse_category()
which also strips leading D and lives in logging.c.

Change-Id: I5f81343e8c7b714a4630e64ba654e391435c4244

include/osmocom/core/logging.h

@@ -428,6 +428,8 @@ int log_parse_category(const char *category);
 void log_set_category_filter(struct log_target *target, int category,
 			       int enable, int level);
 
+const char *log_subsys_name(const struct log_info *log_info, int cat_idx);
+
 /* management of the targets */
 struct log_target *log_target_create(void);
 void log_target_destroy(struct log_target *target);

src/core/libosmocore.map

@@ -67,6 +67,7 @@ logp2;
 log_parse_category;
 log_parse_category_mask;
 log_parse_level;
+log_subsys_name;
 logp_stub;
 log_reset_context;
 log_set_all_filter;

src/core/logging.c

@@ -348,6 +348,13 @@ const char *log_level_str(unsigned int lvl)
 	return get_value_string(loglevel_strs, lvl);
 }
 
+/* skip the leading 'D' in category name */
+const char *log_subsys_name(const struct log_info *log_info, int cat_idx)
+{
+	const char *name = log_info->cat[cat_idx].name;
+	return name + 1;
+}
+
 /*! parse a human-readable log category into numeric form
  *  \param[in] category human-readable log category name
  *  \returns numeric category value, or -EINVAL otherwise
@@ -361,7 +368,7 @@ int log_parse_category(const char *category)
 	for (i = 0; i < osmo_log_info->num_cat; ++i) {
 		if (osmo_log_info->cat[i].name == NULL)
 			continue;
-		if (!strcasecmp(osmo_log_info->cat[i].name+1, category))
+		if (!strcasecmp(log_subsys_name(osmo_log_info, i), category))
 			return i;
 	}
 

src/vty/logging_vty.c

@@ -322,8 +322,7 @@ static void add_category_strings(char **cmd_str_p, char **doc_str_p,
 	for (i = 0; i < categories->num_cat; i++) {
 		if (categories->cat[i].name == NULL)
 			continue;
-		/* skip the leading 'D' in each category name, hence '+ 1' */
-		osmo_str_tolower_buf(buf, sizeof(buf), categories->cat[i].name + 1);
+		osmo_str_tolower_buf(buf, sizeof(buf), log_subsys_name(categories, i));
 		osmo_talloc_asprintf(tall_log_ctx, *cmd_str_p, "%s%s",
 				     i ? "|" : "", buf);
 		osmo_talloc_asprintf(tall_log_ctx, *doc_str_p, "%s\n",
@@ -523,7 +522,7 @@ static void vty_print_logtarget(struct vty *vty, const struct log_info *info,
 		if (!info->cat[i].name)
 			continue;
 		vty_out(vty, "  %-10s %-10s %-8s %s%s",
-			info->cat[i].name+1, log_level_str(cat->loglevel),
+			log_subsys_name(info, i), log_level_str(cat->loglevel),
 			cat->enabled ? "Enabled" : "Disabled",
  			info->cat[i].description,
 			VTY_NEWLINE);
@@ -1088,7 +1087,7 @@ static int config_write_log_single(struct vty *vty, struct log_target *tgt)
 		if (!osmo_log_info->cat[i].name)
 			continue;
 
-		osmo_str_tolower_buf(cat_name, sizeof(cat_name), osmo_log_info->cat[i].name + 1);
+		osmo_str_tolower_buf(cat_name, sizeof(cat_name), log_subsys_name(osmo_log_info, i));
 
 		level_str = get_value_string_or_null(loglevel_strs, cat->loglevel);
 		if (!level_str) {