Merge tag 'usb-5.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb

[linux-2.6-microblaze.git] / samples / trace_events / trace-events-sample.h

diff --git a/samples/trace_events/trace-events-sample.h b/samples/trace_events/trace-events-sample.h
index 13a35f7..e61471a 100644 (file)
--- a/samples/trace_events/trace-events-sample.h
+++ b/samples/trace_events/trace-events-sample.h
@@ -141,6 +141,33 @@
  *         In most cases, the __assign_str() macro will take the same
  *         parameters as the __string() macro had to declare the string.
  *
+ *   __string_len: This is a helper to a __dynamic_array, but it understands
+ *        that the array has characters in it, and with the combined
+ *         use of __assign_str_len(), it will allocate 'len' + 1 bytes
+ *         in the ring buffer and add a '\0' to the string. This is
+ *         useful if the string being saved has no terminating '\0' byte.
+ *         It requires that the length of the string is known as it acts
+ *         like a memcpy().
+ *
+ *         Declared with:
+ *
+ *         __string_len(foo, bar, len)
+ *
+ *         To assign this string, use the helper macro __assign_str_len().
+ *
+ *         __assign_str(foo, bar, len);
+ *
+ *         Then len + 1 is allocated to the ring buffer, and a nul terminating
+ *         byte is added. This is similar to:
+ *
+ *         memcpy(__get_str(foo), bar, len);
+ *         __get_str(foo)[len] = 0;
+ *
+ *        The advantage of using this over __dynamic_array, is that it
+ *        takes care of allocating the extra byte on the ring buffer
+ *        for the '\0' terminating byte, and __get_str(foo) can be used
+ *        in the TP_printk().
+ *
  *   __bitmask: This is another kind of __dynamic_array, but it expects
  *         an array of longs, and the number of bits to parse. It takes
  *         two parameters (name, nr_bits), where name is the name of the