tracing/iwlwifi: Use the new __vstring() helper

Instead of open coding a __dynamic_array() with a fixed length (which
defeats the purpose of the dynamic array in the first place). Use the new
__vstring() helper that will use a va_list and only write enough of the
string into the ring buffer that is needed.

Link: https://lkml.kernel.org/r/20220705224749.806599472@goodmis.org

Cc: Gregory Greenman <gregory.greenman@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Kalle Valo <kvalo@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
Acked-by: Kalle Valo <kvalo@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

drivers/net/wireless/intel/iwlwifi/iwl-devtrace-msg.h

@@ -18,12 +18,10 @@ DECLARE_EVENT_CLASS(iwlwifi_msg_event,
 	TP_PROTO(struct va_format *vaf),
 	TP_ARGS(vaf),
 	TP_STRUCT__entry(
-		__dynamic_array(char, msg, MAX_MSG_LEN)
+		__vstring(msg, vaf->fmt, vaf->va)
 	),
 	TP_fast_assign(
-		WARN_ON_ONCE(vsnprintf(__get_dynamic_array(msg),
-				       MAX_MSG_LEN, vaf->fmt,
-				       *vaf->va) >= MAX_MSG_LEN);
+		__assign_vstr(msg, vaf->fmt, vaf->va);
 	),
 	TP_printk("%s", __get_str(msg))
 );
@@ -55,14 +53,12 @@ TRACE_EVENT(iwlwifi_dbg,
 	TP_STRUCT__entry(
 		__field(u32, level)
 		__string(function, function)
-		__dynamic_array(char, msg, MAX_MSG_LEN)
+		__vstring(msg, vaf->fmt, vaf->va)
 	),
 	TP_fast_assign(
 		__entry->level = level;
 		__assign_str(function, function);
-		WARN_ON_ONCE(vsnprintf(__get_dynamic_array(msg),
-				       MAX_MSG_LEN, vaf->fmt,
-				       *vaf->va) >= MAX_MSG_LEN);
+		__assign_vstr(msg, vaf->fmt, vaf->va);
 	),
 	TP_printk("%s", __get_str(msg))
 );