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The can subsystem communicates with user space using a bcm_msg_head header, which contains two timestamps. This is problematic for multiple reasons: a) The structure layout is currently incompatible between 64-bit user space and 32-bit user space, and cannot work in compat mode (other than x32). b) The timeval structure layout will change in 32-bit user space when we fix the y2038 overflow problem by redefining time_t to 64-bit, making new 32-bit user space incompatible with the current kernel interface. Cars last a long time and often use old kernels, so the actual users of this code are the most likely ones to migrate to y2038 safe user space. This tries to work around part of the problem by changing the publicly visible user interface in the header, but not the binary interface. Fortunately, the values passed around in the structure are relative times and do not actually suffer from the y2038 overflow, so 32-bit is enough here. We replace the use of 'struct timeval' with a newly defined 'struct bcm_timeval' that uses the exact same binary layout as before and that still suffers from problem a) but not problem b). The downside of this approach is that any user space program that currently assigns a timeval structure to these members rather than writing the tv_sec/tv_usec portions individually will suffer a compile-time error when built with an updated kernel header. Fixing this error makes it work fine with old and new headers though. We could address problem a) by using '__u32' or 'int' members rather than 'long', but that would have a more significant downside in also breaking support for all existing 64-bit user binaries that might be using this interface, which is likely not acceptable. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Oliver Hartkopp <socketcan@hartkopp.net> Cc: linux-can@vger.kernel.org Cc: linux-api@vger.kernel.org Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
104 lines
3.9 KiB
C
104 lines
3.9 KiB
C
/*
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* linux/can/bcm.h
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*
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* Definitions for CAN Broadcast Manager (BCM)
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*
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* Author: Oliver Hartkopp <oliver.hartkopp@volkswagen.de>
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* Copyright (c) 2002-2007 Volkswagen Group Electronic Research
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of Volkswagen nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* Alternatively, provided that this notice is retained in full, this
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* software may be distributed under the terms of the GNU General
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* Public License ("GPL") version 2, in which case the provisions of the
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* GPL apply INSTEAD OF those given above.
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*
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* The provided data structures and external interfaces from this code
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* are not restricted to be used by modules with a GPL compatible license.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
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* DAMAGE.
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*/
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#ifndef _UAPI_CAN_BCM_H
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#define _UAPI_CAN_BCM_H
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#include <linux/types.h>
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#include <linux/can.h>
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struct bcm_timeval {
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long tv_sec;
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long tv_usec;
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};
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/**
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* struct bcm_msg_head - head of messages to/from the broadcast manager
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* @opcode: opcode, see enum below.
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* @flags: special flags, see below.
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* @count: number of frames to send before changing interval.
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* @ival1: interval for the first @count frames.
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* @ival2: interval for the following frames.
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* @can_id: CAN ID of frames to be sent or received.
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* @nframes: number of frames appended to the message head.
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* @frames: array of CAN frames.
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*/
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struct bcm_msg_head {
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__u32 opcode;
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__u32 flags;
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__u32 count;
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struct bcm_timeval ival1, ival2;
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canid_t can_id;
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__u32 nframes;
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struct can_frame frames[0];
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};
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enum {
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TX_SETUP = 1, /* create (cyclic) transmission task */
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TX_DELETE, /* remove (cyclic) transmission task */
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TX_READ, /* read properties of (cyclic) transmission task */
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TX_SEND, /* send one CAN frame */
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RX_SETUP, /* create RX content filter subscription */
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RX_DELETE, /* remove RX content filter subscription */
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RX_READ, /* read properties of RX content filter subscription */
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TX_STATUS, /* reply to TX_READ request */
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TX_EXPIRED, /* notification on performed transmissions (count=0) */
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RX_STATUS, /* reply to RX_READ request */
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RX_TIMEOUT, /* cyclic message is absent */
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RX_CHANGED /* updated CAN frame (detected content change) */
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};
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#define SETTIMER 0x0001
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#define STARTTIMER 0x0002
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#define TX_COUNTEVT 0x0004
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#define TX_ANNOUNCE 0x0008
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#define TX_CP_CAN_ID 0x0010
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#define RX_FILTER_ID 0x0020
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#define RX_CHECK_DLC 0x0040
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#define RX_NO_AUTOTIMER 0x0080
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#define RX_ANNOUNCE_RESUME 0x0100
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#define TX_RESET_MULTI_IDX 0x0200
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#define RX_RTR_FRAME 0x0400
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#endif /* !_UAPI_CAN_BCM_H */
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