netconsole: Initialize configfs_item for default targets

For netconsole targets allocated during the boot time (passing
netconsole=... argument), netconsole_target->item is not initialized.
That is not a problem because it is not used inside configfs.

An upcoming patch will be using it, thus, initialize the targets with
the name 'cmdline' plus a counter starting from 0.  This name will match
entries in the configfs later.

Suggested-by: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Breno Leitao <leitao@debian.org>
Link: https://lore.kernel.org/r/20231012111401.333798-3-leitao@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/netconsole.c

@@ -53,6 +53,8 @@ static bool oops_only = false;
 module_param(oops_only, bool, 0600);
 MODULE_PARM_DESC(oops_only, "Only log oops messages");
 
+#define NETCONSOLE_PARAM_TARGET_PREFIX "cmdline"
+
 #ifndef	MODULE
 static int __init option_setup(char *opt)
 {
@@ -165,6 +167,10 @@ static void netconsole_target_put(struct netconsole_target *nt)
 {
 }
 
+static void populate_configfs_item(struct netconsole_target *nt,
+				   int cmdline_count)
+{
+}
 #endif	/* CONFIG_NETCONSOLE_DYNAMIC */
 
 /* Allocate and initialize with defaults.
@@ -688,6 +694,17 @@ static struct configfs_subsystem netconsole_subsys = {
 	},
 };
 
+static void populate_configfs_item(struct netconsole_target *nt,
+				   int cmdline_count)
+{
+	char target_name[16];
+
+	snprintf(target_name, sizeof(target_name), "%s%d",
+		 NETCONSOLE_PARAM_TARGET_PREFIX, cmdline_count);
+	config_item_init_type_name(&nt->item, target_name,
+				   &netconsole_target_type);
+}
+
 #endif	/* CONFIG_NETCONSOLE_DYNAMIC */
 
 /* Handle network interface device notifications */
@@ -887,7 +904,8 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
 }
 
 /* Allocate new target (from boot/module param) and setup netpoll for it */
-static struct netconsole_target *alloc_param_target(char *target_config)
+static struct netconsole_target *alloc_param_target(char *target_config,
+						    int cmdline_count)
 {
 	struct netconsole_target *nt;
 	int err;
@@ -922,6 +940,7 @@ static struct netconsole_target *alloc_param_target(char *target_config)
 	if (err)
 		goto fail;
 
+	populate_configfs_item(nt, cmdline_count);
 	nt->enabled = true;
 
 	return nt;
@@ -954,14 +973,15 @@ static int __init init_netconsole(void)
 {
 	int err;
 	struct netconsole_target *nt, *tmp;
+	unsigned int count = 0;
 	bool extended = false;
 	unsigned long flags;
 	char *target_config;
 	char *input = config;
 
 	if (strnlen(input, MAX_PARAM_LENGTH)) {
 		while ((target_config = strsep(&input, ";"))) {
-			nt = alloc_param_target(target_config);
+			nt = alloc_param_target(target_config, count);
 			if (IS_ERR(nt)) {
 				err = PTR_ERR(nt);
 				goto fail;
@@ -977,6 +997,7 @@ static int __init init_netconsole(void)
 			spin_lock_irqsave(&target_list_lock, flags);
 			list_add(&nt->list, &target_list);
 			spin_unlock_irqrestore(&target_list_lock, flags);
+			count++;
 		}
 	}