header-guard for lib.h

[can-utils.git] / canframelen.h

diff --git a/canframelen.h b/canframelen.h
index 225bc09f756dbb744785fc57abcd26a4aabb2660..4f394047a8a7b118c3fb76407499c7f93bd7afd5 100644 (file)
--- a/canframelen.h
+++ b/canframelen.h
@@ -1,3 +1,48 @@
+/*
+ * canframelen.h
+ *
+ * Copyright (c) 2013, 2014 Czech Technical University in Prague
+ *
+ * Author: Michal Sojka <sojkam1@fel.cvut.cz>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Czech Technical University in Prague nor the
+ *    names of its contributors may be used to endorse or promote
+ *    products derived from this software without specific prior
+ *    written permission.
+ *
+ * Alternatively, provided that this notice is retained in full, this
+ * software may be distributed under the terms of the GNU General
+ * Public License ("GPL") version 2, in which case the provisions of the
+ * GPL apply INSTEAD OF those given above.
+ *
+ * The provided data structures and external interfaces from this code
+ * are not restricted to be used by modules with a GPL compatible license.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * Send feedback to <linux-can@vger.kernel.org>
+ *
+ */
+
 #ifndef CANFRAMELEN_H
 #define CANFRAMELEN_H
 
@@ -6,20 +51,23 @@
 /**
  * Frame length calculation modes.
  *
- * CFL_WORSTCASE corresponds to Ken Tindells *worst* case calculation
- * for stuff-bits (see "Guaranteeing Message Latencies on Controller
- * Area Network" 1st ICC'94) the needed bits on the wire can be
- * calculated as:
+ * CFL_WORSTCASE corresponds to *worst* case calculation for
+ * stuff-bits - see (1)-(3) in [1]. The worst case number of bits on
+ * the wire can be calculated as:
  *
- * (34 + 8n)/5 + 47 + 8n for SFF frames (11 bit CAN-ID) => (269 + 48n)/5
- * (54 + 8n)/5 + 67 + 8n for EFF frames (29 bit CAN-ID) => (389 + 48n)/5
+ * (34 + 8n - 1)/4 + 34 + 8n + 13 for SFF frames (11 bit CAN-ID) => 55 + 10n
+ * (54 + 8n - 1)/4 + 54 + 8n + 13 for EFF frames (29 bit CAN-ID) => 80 + 10n
  *
  * while 'n' is the data length code (number of payload bytes)
  *
+ * [1] "Controller Area Network (CAN) schedulability analysis:
+ *     Refuted, revisited and revised", Real-Time Syst (2007)
+ *     35:239-272.
+ *
  */
 enum cfl_mode {
        CFL_NO_BITSTUFFING, /* plain bit calculation without bitstuffing */
-       CFL_WORSTCASE, /* with bitstuffing following Tindells estimation */
+       CFL_WORSTCASE, /* worst case estimation - see above */
        CFL_EXACT, /* exact calculation of stuffed bits based on frame
                    * content and CRC */
 };