Re: [PATCH v3 04/12] tracing: Add dynamic event command creation interface

Hi Steve,

On Wed, 2020-01-29 at 13:00 -0500, Steven Rostedt wrote:

On Fri, 24 Jan 2020 16:56:15 -0600
Tom Zanussi [off-list ref] wrote:

quoted

+/**
+ * dynevent_arg_add - Add an arg to a dynevent_cmd
+ * @cmd: A pointer to the dynevent_cmd struct representing the new
event cmd
+ * @arg: The argument to append to the current cmd
+ *
+ * Append an argument to a dynevent_cmd.  The argument string will
be
+ * appended to the current cmd string, followed by a separator, if
+ * applicable.  Before the argument is added, the check_arg()
+ * function, if defined, is called.
+ *
+ * The cmd string, separator, and check_arg() function should be
set
+ * using the dynevent_arg_init() before any arguments are added
using
+ * this function.
+ *
+ * Return: 0 if successful, error otherwise.
+ */
+int dynevent_arg_add(struct dynevent_cmd *cmd,
+		     struct dynevent_arg *arg)
+{
+	int ret = 0;
+	int delta;
+	char *q;
+
+	if (arg->check_arg) {
+		ret = arg->check_arg(arg);
+		if (ret)
+			return ret;
+	}
+
+	q = cmd->buf + (cmd->maxlen - cmd->remaining);
+
+	delta = snprintf(q, cmd->remaining, " %s%c", arg->str,
arg->separator);
+	if (delta >= cmd->remaining) {
+		pr_err("String is too long: %s\n", arg->str);
+		return -E2BIG;
+	}
+	cmd->remaining -= delta;

This looks like you can take advantage of the seq_buf code
(see /lib/seq_buf.c), as that handles a lot of this for you.

As I'm trying to get this into the merge window, I won't delay this
for
that (unless I find something else to delay this for), but this
should
definitely incorporate seq_buf and not handle its own buffering.

OK, I can send a follow-on patch that does this.

Note that I just sent a v4 series which moves most of the code in this
patch to trace_dynevent.{c,h} as requested by Masami.  No other changes
from v3 were made other than adding acks.

Thanks,

Tom  

-- Steve

quoted

+
+	return ret;
+}