path: root/drivers/net/can/dev.c

/*
 * Copyright (C) 2005 Marc Kleine-Budde, Pengutronix
 * Copyright (C) 2006 Andrey Volkov, Varma Electronics
 * Copyright (C) 2008-2009 Wolfgang Grandegger <wg@grandegger.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the version 2 of the GNU General Public License
 * as published by the Free Software Foundation
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/can.h>
#include <linux/can/dev.h>
#include <linux/can/skb.h>
#include <linux/can/netlink.h>
#include <linux/can/led.h>
#include <net/rtnetlink.h>

#define MOD_DESC "CAN device driver interface"

MODULE_DESCRIPTION(MOD_DESC);
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Wolfgang Grandegger <wg@grandegger.com>");

/* CAN DLC to real data length conversion helpers */

static const u8 dlc2len[] = {0, 1, 2, 3, 4, 5, 6, 7,
			     8, 12, 16, 20, 24, 32, 48, 64};

/* get data length from can_dlc with sanitized can_dlc */
u8 can_dlc2len(u8 can_dlc)
{
	return dlc2len[can_dlc & 0x0F];
}
EXPORT_SYMBOL_GPL(can_dlc2len);

static const u8 len2dlc[] = {0, 1, 2, 3, 4, 5, 6, 7, 8,		/* 0 - 8 */
			     9, 9, 9, 9,			/* 9 - 12 */
			     10, 10, 10, 10,			/* 13 - 16 */
			     11, 11, 11, 11,			/* 17 - 20 */
			     12, 12, 12, 12,			/* 21 - 24 */
			     13, 13, 13, 13, 13, 13, 13, 13,	/* 25 - 32 */
			     14, 14, 14, 14, 14, 14, 14, 14,	/* 33 - 40 */
			     14, 14, 14, 14, 14, 14, 14, 14,	/* 41 - 48 */
			     15, 15, 15, 15, 15, 15, 15, 15,	/* 49 - 56 */
			     15, 15, 15, 15, 15, 15, 15, 15};	/* 57 - 64 */

/* map the sanitized data length to an appropriate data length code */
u8 can_len2dlc(u8 len)
{
	if (unlikely(len > 64))
		return 0xF;

	return len2dlc[len];
}
EXPORT_SYMBOL_GPL(can_len2dlc);

#ifdef CONFIG_CAN_CALC_BITTIMING
#define CAN_CALC_MAX_ERROR 50 /* in one-tenth of a percent */

/*
 * Bit-timing calculation derived from:
 *
 * Code based on LinCAN sources and H8S2638 project
 * Copyright 2004-2006 Pavel Pisa - DCE FELK CVUT cz
 * Copyright 2005      Stanislav Marek
 * email: pisa@cmp.felk.cvut.cz
 *
 * Calculates proper bit-timing parameters for a specified bit-rate
 * and sample-point, which can then be used to set the bit-timing
 * registers of the CAN controller. You can find more information
 * in the header file linux/can/netlink.h.
 */
static int can_update_spt(const struct can_bittiming_const *btc,
			  int sampl_pt, int tseg, int *tseg1, int *tseg2)
{
	*tseg2 = tseg + 1 - (sampl_pt * (tseg + 1)) / 1000;
	if (*tseg2 < btc->tseg2_min)
		*tseg2 = btc->tseg2_min;
	if (*tseg2 > btc->tseg2_max)
		*tseg2 = btc->tseg2_max;
	*tseg1 = tseg - *tseg2;
	if (*tseg1 > btc->tseg1_max) {
		*tseg1 = btc->tseg1_max;
		*tseg2 = tseg - *tseg1;
	}
	return 1000 * (tseg + 1 - *tseg2) / (tseg + 1);
}

static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
			      const struct can_bittiming_const *btc)
{
	struct can_priv *priv = netdev_priv(dev);
	long rate, best_rate = 0;
	long best_error = 1000000000, error = 0;
	int best_tseg = 0, best_brp = 0, brp = 0;
	int tsegall, tseg = 0, tseg1 = 0, tseg2 = 0;
	int spt_error = 1000, spt = 0, sampl_pt;
	u64 v64;

	/* Use CIA recommended sample points */
	if (bt->sample_point) {
		sampl_pt = bt->sample_point;
	} else {
		if (bt->bitrate > 800000)
			sampl_pt = 750;
		else if (bt->bitrate > 500000)
			sampl_pt = 800;
		else
			sampl_pt = 875;
	}

	/* tseg even = round down, odd = round up */
	for (tseg = (btc->tseg1_max + btc->tseg2_max) * 2 + 1;
	     tseg >= (btc->tseg1_min + btc->tseg2_min) * 2; tseg--) {
		tsegall = 1 + tseg / 2;
		/* Compute all possible tseg choices (tseg=tseg1+tseg2) */
		brp = priv->clock.freq<