can3--socketcan之mcp251x.c

函数原型源于2.6.38
******************************************************************

spi驱动结构见
http://blog.csdn.net/songqqnew/article/details/7037583

mcp251x.c和dm9000.c驱动模式类似
参考 

dm9000 driver 1

理清一下驱动的线索
******************************************************************

在init函数中注册spi驱动mcp251x_can_driver

static int __init mcp251x_can_init(void){DBG("init\n");return spi_register_driver(&mcp251x_can_driver);}

在spi驱动mcp251x_can_driver的probe函数中分配net_device

static struct spi_driver mcp251x_can_driver = {.driver = {.name = DEVICE_NAME,//mcp2515.bus = &spi_bus_type,.owner = THIS_MODULE,},.id_table = mcp251x_id_table,.probe = mcp251x_can_probe,//probe.remove = __devexit_p(mcp251x_can_remove),.suspend = mcp251x_can_suspend,.resume = mcp251x_can_resume,};static int __devinit mcp251x_can_probe(struct spi_device *spi){net = alloc_candev(sizeof(struct mcp251x_priv), TX_ECHO_SKB_MAX);if (!net) {ret = -ENOMEM;goto error_alloc;}//注册net_deviceregister_candev(net);//net_device的operation结构体指定了操作函数集合 static const struct net_device_ops mcp251x_netdev_ops = {.ndo_open = mcp251x_open,.ndo_stop = mcp251x_stop,.ndo_start_xmit = mcp251x_hard_start_xmit,};}

应用层执行ifconfig can0 up时会调用到mcp251x_open
在mcp251x_open函数中,

//打开设备open_candev(net);//申请中断ret = request_irq(spi->irq, mcp251x_can_irq, /*IRQF_DISABLED |*/ IRQF_TRIGGER_LOW ,  DEVICE_NAME, priv);//初始化工作队列，当做中断(接收)下半部，用于处理接收INIT_WORK(&priv->irq_work,can_irq_work);//初始化工作队列，用于处理发送INIT_WORK(&priv->tx_work, mcp251x_tx_work_handler);

应用层执行write socket时会调用到mcp251x_hard_start_xmit，
在 mcp251x_hard_start_xmit函数中，

//停止协议栈向驱动发送数据(在发送数据的时候需要停止协议栈发来新的需要发送出去的数据)，发送完成后会重新启用netif_stop_queue(net);//启动发送工作队列，将数据(skb)发送出去priv->tx_skb = skb;queue_work(priv->wq, &priv->tx_work);

具体看一下这个发送工作队列函数

static void mcp251x_tx_work_handler(struct work_struct *ws){struct mcp251x_priv *priv = container_of(ws, struct mcp251x_priv, tx_work);struct spi_device *spi = priv->spi;struct net_device *net = priv->net;struct can_frame *frame;//printk("mcp251x_tx_work_handler\n");mutex_lock(&priv->mcp_lock);if (priv->tx_skb) {if (priv->can.state == CAN_STATE_BUS_OFF) {mcp251x_clean(net);} else {frame = (struct can_frame *)priv->tx_skb->data;if (frame->can_dlc > CAN_FRAME_MAX_DATA_LEN)frame->can_dlc = CAN_FRAME_MAX_DATA_LEN;mcp251x_hw_tx(spi, frame, 0);priv->tx_len = 1 + frame->can_dlc;can_put_echo_skb(priv->tx_skb, net, 0);priv->tx_skb = NULL;}}mutex_unlock(&priv->mcp_lock);}

怎么接收呢？当然是在中断处理函数中接收，有中断产生时，会启用一个负责接受的工作队列，即中断下半部，去接收。并将接收到的数据保存，以供应用层使用read socket等来读取。

static irqreturn_t mcp251x_can_irq(int irq, void *dev_id){DBG("zhongduan :mcp251x_can_irq\n");       struct mcp251x_priv *priv = dev_id;        disable_irq_nosync(irq);//禁止中断，工作队列函数中接收完成时会重新使能中断       if (!work_pending(&priv->irq_work))queue_work(priv->wq, &priv->irq_work);//调用工作队列函数       return IRQ_HANDLED;}

接收工作队列函数

void can_irq_work(struct work_struct *ws){DBG("zhongduan bottom: can_irq_work\n");     struct mcp251x_priv *priv = container_of(ws, struct mcp251x_priv, irq_work);     struct spi_device *spi = priv->spi;     struct net_device *net = priv->net;mutex_lock(&priv->mcp_lock);        //mcp251x_write_reg(spi, CANINTE, (intset & (~ ( CANINTE_TX2IE) )));while (!priv->force_quit) {enum can_state new_state;u8 intf, eflag;      u8 clear_intf = 0;int can_id = 0, data1 = 0;               mcp251x_read_2regs(spi, CANINTF, &intf, &eflag);                DBG("intf=%x\n",intf);//一般返回1，表示rxb0里有数据。                //mcp251x_write_bits(spi, CANINTF, intf, 0x00);        /* mask out flags we don't care about */intf &= CANINTF_RX | CANINTF_TX | CANINTF_ERR ;//| CANINTF_MERRF;                if (intf & CANINTF_TX) {//如果是发送完成中断net->stats.tx_packets++;net->stats.tx_bytes += priv->tx_len - 1;if (priv->tx_len) {can_get_echo_skb(net, 0);priv->tx_len = 0;}netif_wake_queue(net);//重新开启}/* receive buffer 1 */if (intf & CANINTF_RX1IF) {//如果是从mcp251x的buffer 1接收到数据的中断mcp251x_hw_rx(spi, 1);//接收/* the MCP2515 does this automatically */if (mcp251x_is_2510(spi))clear_intf |= CANINTF_RX1IF;//清除mcp251x里的中断标志}                /* receive buffer 0 */if (intf & CANINTF_RX0IF) {//如果是从mcp251x的buffer 0接收到数据的中断mcp251x_hw_rx(spi, 0);//接收mcp2515的rxb0里的数据，见下/* * Free one buffer ASAP * (The MCP2515 does this automatically.) */if (mcp251x_is_2510(spi))mcp251x_write_bits(spi, CANINTF, CANINTF_RX0IF, 0x00);//清除mcp251x里的中断标志}   /* any error or tx interrupt we need to clear? */if (intf & (CANINTF_ERR | CANINTF_TX))clear_intf |= intf & (CANINTF_ERR | CANINTF_TX);if (clear_intf)mcp251x_write_bits(spi, CANINTF, clear_intf, 0x00);if (eflag)mcp251x_write_bits(spi, EFLG, eflag, 0x00);               /* Update can state */if (eflag & EFLG_TXBO) {new_state = CAN_STATE_BUS_OFF;can_id |= CAN_ERR_BUSOFF;} else if (eflag & EFLG_TXEP) {new_state = CAN_STATE_ERROR_PASSIVE;can_id |= CAN_ERR_CRTL;data1 |= CAN_ERR_CRTL_TX_PASSIVE;} else if (eflag & EFLG_RXEP) {new_state = CAN_STATE_ERROR_PASSIVE;can_id |= CAN_ERR_CRTL;data1 |= CAN_ERR_CRTL_RX_PASSIVE;} else if (eflag & EFLG_TXWAR) {new_state = CAN_STATE_ERROR_WARNING;can_id |= CAN_ERR_CRTL;data1 |= CAN_ERR_CRTL_TX_WARNING;} else if (eflag & EFLG_RXWAR) {new_state = CAN_STATE_ERROR_WARNING;can_id |= CAN_ERR_CRTL;data1 |= CAN_ERR_CRTL_RX_WARNING;} else {new_state = CAN_STATE_ERROR_ACTIVE;}/* Update can state statistics */switch (priv->can.state) {case CAN_STATE_ERROR_ACTIVE:if (new_state >= CAN_STATE_ERROR_WARNING &&    new_state <= CAN_STATE_BUS_OFF)priv->can.can_stats.error_warning++;case CAN_STATE_ERROR_WARNING:/* fallthrough */if (new_state >= CAN_STATE_ERROR_PASSIVE &&    new_state <= CAN_STATE_BUS_OFF)priv->can.can_stats.error_passive++;break;default:break;}priv->can.state = new_state;if (intf & CANINTF_ERRIF) {/* Handle overflow counters */if (eflag & (EFLG_RX0OVR | EFLG_RX1OVR)) {if (eflag & EFLG_RX0OVR) {net->stats.rx_over_errors++;net->stats.rx_errors++;}if (eflag & EFLG_RX1OVR) {net->stats.rx_over_errors++;net->stats.rx_errors++;}can_id |= CAN_ERR_CRTL;data1 |= CAN_ERR_CRTL_RX_OVERFLOW;}mcp251x_error_skb(net, can_id, data1);}if (priv->can.state == CAN_STATE_BUS_OFF) {if (priv->can.restart_ms == 0) {priv->force_quit = 1;can_bus_off(net);mcp251x_hw_sleep(spi);break;}}                if (intf == 0)break;}        //mcp251x_write_reg(spi, CANINTE, intset);mutex_unlock(&priv->mcp_lock);                 enable_irq(spi->irq);//重新使能中断        //s3c_gpio_cfgpin(S3C64XX_GPL(8), S3C_GPIO_SFN(3));   }

附mcp251x.c源码

/* * CAN bus driver for Microchip 251x CAN Controller with SPI Interface * * MCP2510 support and bug fixes by Christian Pellegrin * <[e-mail]> * * Copyright 2009 Christian Pellegrin EVOL S.r.l. * * Copyright 2007 Raymarine UK, Ltd. All Rights Reserved. * Written under contract by: *   Chris Elston, Katalix Systems, Ltd. * * Based on Microchip MCP251x CAN controller driver written by * David Vrabel, Copyright 2006 Arcom Control Systems Ltd. * * Based on CAN bus driver for the CCAN controller written by * - Sascha Hauer, Marc Kleine-Budde, Pengutronix * - Simon Kallweit, intefo AG * Copyright 2007 * * 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, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA * * * * Your platform definition file should specify something like: * * static struct mcp251x_platform_data mcp251x_info = { *         .oscillator_frequency = 8000000, *         .board_specific_setup = &mcp251x_setup, *         .power_enable = mcp251x_power_enable, *         .transceiver_enable = NULL, * }; * * static struct spi_board_info spi_board_info[] = { *         { *                 .modalias = "mcp2510", *            // or "mcp2515" depending on your controller *                 .platform_data = &mcp251x_info, *                 .irq = IRQ_EINT13, *                 .max_speed_hz = 2*1000*1000, *                 .chip_select = 2, *         }, * }; * * Please see mcp251x.h for a description of the fields in * struct mcp251x_platform_data. * */#define DEBUG  #ifdef DEBUG    #define DBG(...) printk(" DBG(%s, %s(), %d): ", __FILE__, __FUNCTION__, __LINE__); printk(__VA_ARGS__)    #else    #define DBG(...)    #endif    #include <linux/can/core.h>#include <linux/can/dev.h>#include <linux/can/platform/mcp251x.h>#include <linux/completion.h>#include <linux/delay.h>#include <linux/device.h>#include <linux/dma-mapping.h>#include <linux/freezer.h>#include <linux/interrupt.h>#include <linux/io.h>#include <linux/kernel.h>#include <linux/module.h>#include <linux/netdevice.h>#include <linux/platform_device.h>#include <linux/slab.h>#include <linux/spi/spi.h>#include <linux/uaccess.h>#include <linux/gpio.h>#include <plat/gpio-cfg.h>/* SPI interface instruction set */#define INSTRUCTION_WRITE    0x02#define INSTRUCTION_READ    0x03#define INSTRUCTION_BIT_MODIFY    0x05#define INSTRUCTION_LOAD_TXB(n)    (0x40 + 2 * (n))#define INSTRUCTION_READ_RXB(n)    (((n) == 0) ? 0x90 : 0x94)#define INSTRUCTION_RESET    0xC0/* MPC251x registers */#define CANSTAT          0x0e#define CANCTRL          0x0f#  define CANCTRL_REQOP_MASK        0xe0#  define CANCTRL_REQOP_CONF        0x80#  define CANCTRL_REQOP_LISTEN_ONLY 0x60#  define CANCTRL_REQOP_LOOPBACK    0x40#  define CANCTRL_REQOP_SLEEP        0x20#  define CANCTRL_REQOP_NORMAL        0x00#  define CANCTRL_OSM            0x08#  define CANCTRL_ABAT            0x10#define TEC          0x1c#define REC          0x1d#define CNF1          0x2a#  define CNF1_SJW_SHIFT   6#define CNF2          0x29#  define CNF2_BTLMODE       0x80#  define CNF2_SAM         0x40#  define CNF2_PS1_SHIFT   3#define CNF3          0x28#  define CNF3_SOF       0x08#  define CNF3_WAKFIL       0x04#  define CNF3_PHSEG2_MASK 0x07#define CANINTE          0x2b#  define CANINTE_MERRE 0x80#  define CANINTE_WAKIE 0x40#  define CANINTE_ERRIE 0x20#  define CANINTE_TX2IE 0x10#  define CANINTE_TX1IE 0x08#  define CANINTE_TX0IE 0x04#  define CANINTE_RX1IE 0x02#  define CANINTE_RX0IE 0x01#define CANINTF          0x2c#  define CANINTF_MERRF 0x80#  define CANINTF_WAKIF 0x40#  define CANINTF_ERRIF 0x20#  define CANINTF_TX2IF 0x10#  define CANINTF_TX1IF 0x08#  define CANINTF_TX0IF 0x04#  define CANINTF_RX1IF 0x02#  define CANINTF_RX0IF 0x01#  define CANINTF_RX (CANINTF_RX0IF | CANINTF_RX1IF)#  define CANINTF_TX (CANINTF_TX2IF | CANINTF_TX1IF | CANINTF_TX0IF)#  define CANINTF_ERR (CANINTF_ERRIF)#define EFLG          0x2d#  define EFLG_EWARN    0x01#  define EFLG_RXWAR    0x02#  define EFLG_TXWAR    0x04#  define EFLG_RXEP    0x08#  define EFLG_TXEP    0x10#  define EFLG_TXBO    0x20#  define EFLG_RX0OVR    0x40#  define EFLG_RX1OVR    0x80#define TXBCTRL(n)  (((n) * 0x10) + 0x30 + TXBCTRL_OFF)#  define TXBCTRL_ABTF    0x40#  define TXBCTRL_MLOA    0x20#  define TXBCTRL_TXERR 0x10#  define TXBCTRL_TXREQ 0x08#define TXBSIDH(n)  (((n) * 0x10) + 0x30 + TXBSIDH_OFF)#  define SIDH_SHIFT    3#define TXBSIDL(n)  (((n) * 0x10) + 0x30 + TXBSIDL_OFF)#  define SIDL_SID_MASK    7#  define SIDL_SID_SHIFT   5#  define SIDL_EXIDE_SHIFT 3#  define SIDL_EID_SHIFT   16#  define SIDL_EID_MASK    3#define TXBEID8(n)  (((n) * 0x10) + 0x30 + TXBEID8_OFF)#define TXBEID0(n)  (((n) * 0x10) + 0x30 + TXBEID0_OFF)#define TXBDLC(n)   (((n) * 0x10) + 0x30 + TXBDLC_OFF)#  define DLC_RTR_SHIFT    6#define TXBCTRL_OFF 0#define TXBSIDH_OFF 1#define TXBSIDL_OFF 2#define TXBEID8_OFF 3#define TXBEID0_OFF 4#define TXBDLC_OFF  5#define TXBDAT_OFF  6#define RXBCTRL(n)  (((n) * 0x10) + 0x60 + RXBCTRL_OFF)#  define RXBCTRL_BUKT    0x04#  define RXBCTRL_RXM0    0x20#  define RXBCTRL_RXM1    0x40#define RXBSIDH(n)  (((n) * 0x10) + 0x60 + RXBSIDH_OFF)#  define RXBSIDH_SHIFT 3#define RXBSIDL(n)  (((n) * 0x10) + 0x60 + RXBSIDL_OFF)#  define RXBSIDL_IDE   0x08#  define RXBSIDL_SRR   0x10#  define RXBSIDL_EID   3#  define RXBSIDL_SHIFT 5#define RXBEID8(n)  (((n) * 0x10) + 0x60 + RXBEID8_OFF)#define RXBEID0(n)  (((n) * 0x10) + 0x60 + RXBEID0_OFF)#define RXBDLC(n)   (((n) * 0x10) + 0x60 + RXBDLC_OFF)#  define RXBDLC_LEN_MASK  0x0f#  define RXBDLC_RTR       0x40#define RXBCTRL_OFF 0#define RXBSIDH_OFF 1#define RXBSIDL_OFF 2#define RXBEID8_OFF 3#define RXBEID0_OFF 4#define RXBDLC_OFF  5#define RXBDAT_OFF  6#define RXFSIDH(n) ((n) * 4)#define RXFSIDL(n) ((n) * 4 + 1)#define RXFEID8(n) ((n) * 4 + 2)#define RXFEID0(n) ((n) * 4 + 3)#define RXMSIDH(n) ((n) * 4 + 0x20)#define RXMSIDL(n) ((n) * 4 + 0x21)#define RXMEID8(n) ((n) * 4 + 0x22)#define RXMEID0(n) ((n) * 4 + 0x23)#define GET_BYTE(val, byte)            \    (((val) >> ((byte) * 8)) & 0xff)#define SET_BYTE(val, byte)            \    (((val) & 0xff) << ((byte) * 8))/* * Buffer size required for the largest SPI transfer (i.e., reading a * frame) */#define CAN_FRAME_MAX_DATA_LEN    8#define SPI_TRANSFER_BUF_LEN    (6 + CAN_FRAME_MAX_DATA_LEN)#define CAN_FRAME_MAX_BITS    128#define TX_ECHO_SKB_MAX    1#define DEVICE_NAME "mcp2515"//static struct timer_list check_timer;void can_irq_work(struct work_struct *ws);//static struct work_struct can_work;static int intset;//中断设置static int mcp251x_enable_dma; /* Enable SPI DMA. Default: 0 (Off) */module_param(mcp251x_enable_dma, int, S_IRUGO);MODULE_PARM_DESC(mcp251x_enable_dma, "Enable SPI DMA. Default: 0 (Off)");static struct can_bittiming_const mcp251x_bittiming_const = {    .name = DEVICE_NAME,    .tseg1_min = 3,    .tseg1_max = 16,    .tseg2_min = 2,    .tseg2_max = 8,    .sjw_max = 4,    .brp_min = 1,    .brp_max = 64,    .brp_inc = 1,};enum mcp251x_model {    CAN_MCP251X_MCP2510    = 0x2510,    CAN_MCP251X_MCP2515    = 0x2515,};struct mcp251x_priv {    struct can_priv       can;    struct net_device *net;    struct spi_device *spi;    enum mcp251x_model model;    struct mutex mcp_lock; /* SPI device lock */    u8 *spi_tx_buf;    u8 *spi_rx_buf;    dma_addr_t spi_tx_dma;    dma_addr_t spi_rx_dma;    struct sk_buff *tx_skb;    int tx_len;    struct workqueue_struct *wq;    struct work_struct tx_work;    struct work_struct restart_work;        struct work_struct irq_work;    int force_quit;    int after_suspend;#define AFTER_SUSPEND_UP 1#define AFTER_SUSPEND_DOWN 2#define AFTER_SUSPEND_POWER 4#define AFTER_SUSPEND_RESTART 8    int restart_tx;};#define MCP251X_IS(_model) \static inline int mcp251x_is_##_model(struct spi_device *spi) \{ \    struct mcp251x_priv *priv = dev_get_drvdata(&spi->dev); \    return priv->model == CAN_MCP251X_MCP##_model; \}MCP251X_IS(2510);MCP251X_IS(2515);static void mcp251x_clean(struct net_device *net){    struct mcp251x_priv *priv = netdev_priv(net);//    DBG("mcp251x_clean\n");    if (priv->tx_skb || priv->tx_len)        net->stats.tx_errors++;    if (priv->tx_skb)        dev_kfree_skb(priv->tx_skb);    if (priv->tx_len)        can_free_echo_skb(priv->net, 0);    priv->tx_skb = NULL;    priv->tx_len = 0;}/* * Note about handling of error return of mcp251x_spi_trans: accessing * registers via SPI is not really different conceptually than using * normal I/O assembler instructions, although it's much more * complicated from a practical POV. So it's not advisable to always * check the return value of this function. Imagine that every * read{b,l}, write{b,l} and friends would be bracketed in "if ( < 0) * error();", it would be a great mess (well there are some situation * when exception handling C++ like could be useful after all). So we * just check that transfers are OK at the beginning of our * conversation with the chip and to avoid doing really nasty things * (like injecting bogus packets in the network stack). */static int mcp251x_spi_trans(struct spi_device *spi, int len){    struct mcp251x_priv *priv = dev_get_drvdata(&spi->dev);    struct spi_transfer t = {        .tx_buf = priv->spi_tx_buf,        .rx_buf = priv->spi_rx_buf,        .len = len,        .cs_change = 0,    };    struct spi_message m;    int ret;//    DBG("mcp251x_spi_trans\n");    spi_message_init(&m);    if (mcp251x_enable_dma) {        t.tx_dma = priv->spi_tx_dma;        t.rx_dma = priv->spi_rx_dma;        m.is_dma_mapped = 1;    }    spi_message_add_tail(&t, &m);    ret = spi_sync(spi, &m);        //ret= spi_async (spi,&m);    if (ret)        dev_err(&spi->dev, "spi transfer failed: ret = %d\n", ret);           int i=0;DBG("打印spi直接发送的数据\n");for( i=0;i<len;i++){DBG("priv->spi_tx_buf[%d]=%x\n",i,priv->spi_tx_buf[i]);}DBG("打印spi直接收到的数据\n");for( i=0;i<len;i++){DBG("priv->spi_rx_buf[%d]=%x\n",i,priv->spi_rx_buf[i]);}    return ret;}static u8 mcp251x_read_reg(struct spi_device *spi, uint8_t reg){    struct mcp251x_priv *priv = dev_get_drvdata(&spi->dev);    u8 val = 0; //INSTRUCTION_READ=3//根据mcp2515手册p64，使用spi接口读取寄存器的步骤是发送 命令03+地址//接收到的寄存器数据在spi_rx_buf[2]    priv->spi_tx_buf[0] = INSTRUCTION_READ;    priv->spi_tx_buf[1] = reg;    mcp251x_spi_trans(spi, 3);    val = priv->spi_rx_buf[2];    return val;}static void mcp251x_read_2regs(struct spi_device *spi, uint8_t reg,        uint8_t *v1, uint8_t *v2){    struct mcp251x_priv *priv = dev_get_drvdata(&spi->dev);    priv->spi_tx_buf[0] = INSTRUCTION_READ;    priv->spi_tx_buf[1] = reg;    mcp251x_spi_trans(spi, 4);////接收到的寄存器数据在spi_rx_buf[2]，spi_rx_buf[3]    *v1 = priv->spi_rx_buf[2];    *v2 = priv->spi_rx_buf[3];}static void mcp251x_write_reg(struct spi_device *spi, u8 reg, uint8_t val){        struct mcp251x_priv *priv = dev_get_drvdata(&spi->dev); //INSTRUCTION_WRITE=2//根据mcp2515手册p64，使用spi接口写寄存器的步骤是发送 命令02+地址+值    priv->spi_tx_buf[0] = INSTRUCTION_WRITE;    priv->spi_tx_buf[1] = reg;    priv->spi_tx_buf[2] = val;    mcp251x_spi_trans(spi, 3);}static void mcp251x_write_bits(struct spi_device *spi, u8 reg,                   u8 mask, uint8_t val){    struct mcp251x_priv *priv = dev_get_drvdata(&spi->dev);//INSTRUCTION_BIT_MODIFY=5//位修改指令，对可执行位操作的寄存器有效    priv->spi_tx_buf[0] = INSTRUCTION_BIT_MODIFY;    priv->spi_tx_buf[1] = reg;    priv->spi_tx_buf[2] = mask;    priv->spi_tx_buf[3] = val;    mcp251x_spi_trans(spi, 4);}static void mcp251x_hw_tx_frame(struct spi_device *spi, u8 *buf,                int len, int tx_buf_idx){    struct mcp251x_priv *priv = dev_get_drvdata(&spi->dev);//如果是2510,还需要指定使用那个发送缓冲区发送数据//    if (mcp251x_is_2510(spi)) {        int i;        for (i = 1; i < TXBDAT_OFF + len; i++)            mcp251x_write_reg(spi, TXBCTRL(tx_buf_idx) + i,                      buf[i]);    } else {        memcpy(priv->spi_tx_buf, buf, TXBDAT_OFF + len);        mcp251x_spi_trans(spi, TXBDAT_OFF + len);    }}static void mcp251x_hw_tx(struct spi_device *spi, struct can_frame *frame,              int tx_buf_idx){    u32 sid, eid, exide, rtr;    u8 buf[SPI_TRANSFER_BUF_LEN];    exide = (frame->can_id & CAN_EFF_FLAG) ? 1 : 0; /* Extended ID Enable */DBG("打印是否扩展帧\n");    if (exide)        {        sid = (frame->can_id & CAN_EFF_MASK) >> 18;        DBG("是扩展帧\n");        }    else        {        sid = frame->can_id & CAN_SFF_MASK; /* Standard ID */        DBG("是标准帧\n");        }    eid = frame->can_id & CAN_EFF_MASK; /* Extended ID */    rtr = (frame->can_id & CAN_RTR_FLAG) ? 1 : 0; /* Remote transmission *///INSTRUCTION_LOAD_TXB(0)=0x40,即装载tx0缓冲器    buf[TXBCTRL_OFF] = INSTRUCTION_LOAD_TXB(tx_buf_idx);    buf[TXBSIDH_OFF] = sid >> SIDH_SHIFT;    buf[TXBSIDL_OFF] = ((sid & SIDL_SID_MASK) << SIDL_SID_SHIFT) |        (exide << SIDL_EXIDE_SHIFT) |        ((eid >> SIDL_EID_SHIFT) & SIDL_EID_MASK);    buf[TXBEID8_OFF] = GET_BYTE(eid, 1);    buf[TXBEID0_OFF] = GET_BYTE(eid, 0);    buf[TXBDLC_OFF] = (rtr << DLC_RTR_SHIFT) | frame->can_dlc;    memcpy(buf + TXBDAT_OFF, frame->data, frame->can_dlc);int i;DBG("打印送给spi的数据\n");for(i=0;i<SPI_TRANSFER_BUF_LEN;i++){DBG("buf[%d]=%x\n",i,buf[i]);}    mcp251x_hw_tx_frame(spi, buf, frame->can_dlc, tx_buf_idx);//装载到tx0缓冲器    mcp251x_write_reg(spi, TXBCTRL(tx_buf_idx), TXBCTRL_TXREQ);//请求发送tx0}static void mcp251x_hw_rx_frame(struct spi_device *spi, u8 *buf,                int buf_idx){    struct mcp251x_priv *priv = dev_get_drvdata(&spi->dev);//        DBG("mcp251x_hw_rx_frame\n");DBG("打印是否是mcp2515\n");    if (mcp251x_is_2510(spi)) {DBG("是mcp2510\n");        int i, len;        for (i = 1; i < RXBDAT_OFF; i++)            buf[i] = mcp251x_read_reg(spi, RXBCTRL(buf_idx) + i);        len = get_can_dlc(buf[RXBDLC_OFF] & RXBDLC_LEN_MASK);        for (; i < (RXBDAT_OFF + len); i++)            buf[i] = mcp251x_read_reg(spi, RXBCTRL(buf_idx) + i);    } else {DBG("是mcp2515\n");//INSTRUCTION_READ_RXB(0)=90,即读取rx0缓冲器        priv->spi_tx_buf[RXBCTRL_OFF] = INSTRUCTION_READ_RXB(buf_idx);/*SPI_TRANSFER_BUF_LEN=14，即spi的发送和接收缓冲区都设为14因为mcp2515共返回14个字节，假如是读rxbuf0,则RXBOCTRLRXB0SIDHRXB0SIDLRXB0EID8RXB0EID0RXB0DLCRXB0D0...RXB0D7*/        mcp251x_spi_trans(spi, SPI_TRANSFER_BUF_LEN);        memcpy(buf, priv->spi_rx_buf, SPI_TRANSFER_BUF_LEN);    }}static void mcp251x_hw_rx(struct spi_device *spi, int buf_idx){    struct mcp251x_priv *priv = dev_get_drvdata(&spi->dev);    struct sk_buff *skb;    struct can_frame *frame;    u8 buf[SPI_TRANSFER_BUF_LEN];//    DBG("mcp251x_hw_rx\n");    skb = alloc_can_skb(priv->net, &frame);    if (!skb) {        dev_err(&spi->dev, "cannot allocate RX skb\n");        priv->net->stats.rx_dropped++;        return;    }    mcp251x_hw_rx_frame(spi, buf, buf_idx);// 接收数据DBG("打印从spi接收到buf里的数据\n");    DBG(" buf_idx=%d\n",buf_idx);    int i;    for(i=0;i<SPI_TRANSFER_BUF_LEN;i++)    {    DBG(" buf[%d]=%x\n",i,buf[i]);    }DBG("打印是否是扩展帧\n");    if (buf[RXBSIDL_OFF] & RXBSIDL_IDE) {//buf[RXBSIDL_OFF]即buf[2]即寄存器RXBnSIDL的第4位表示是否是扩展帧DBG("是扩展帧\n");        /* Extended ID format */        frame->can_id = CAN_EFF_FLAG;        frame->can_id |=            /* Extended ID part */            SET_BYTE(buf[RXBSIDL_OFF] & RXBSIDL_EID, 2) |            SET_BYTE(buf[RXBEID8_OFF], 1) |            SET_BYTE(buf[RXBEID0_OFF], 0) |            /* Standard ID part */            (((buf[RXBSIDH_OFF] << RXBSIDH_SHIFT) |              (buf[RXBSIDL_OFF] >> RXBSIDL_SHIFT)) << 18);        /* Remote transmission request */        if (buf[RXBDLC_OFF] & RXBDLC_RTR)            frame->can_id |= CAN_RTR_FLAG;    } else {DBG("是标准帧\n");        /* Standard ID format *///RXBSIDH的全8位和RXBSIDL的高3位即11位共同组成标准帧的标识符，详见mcp2515手册，//所以理论上一条can总线最多可分辨2048个设备(扩展帧也是11位标识符)//如果//buf[1]=寄存器RXBSIDH=0x24=0010 0100,<<3=0010 0100 000//buf[2]=寄存器RXBSIDL=0x60=0110 0000,>>5=011//加上之后=001 0010 0011=0x123        frame->can_id =            (buf[RXBSIDH_OFF] << RXBSIDH_SHIFT) |            (buf[RXBSIDL_OFF] >> RXBSIDL_SHIFT);        if (buf[RXBSIDL_OFF] & RXBSIDL_SRR)            frame->can_id |= CAN_RTR_FLAG;    }    /* Data length *///buf[3]=寄存器RXBEID8，标准帧不使用//buf[4]=寄存器RXBEID0，标准帧不使用//buf[5]=寄存器RXBDLC=数据段长度    frame->can_dlc = get_can_dlc(buf[RXBDLC_OFF] & RXBDLC_LEN_MASK);//buf[6]-buf[13]=8个数据寄存器RXB0D0-RXB0D7    memcpy(frame->data, buf + RXBDAT_OFF, frame->can_dlc);DBG("打印can_frame的字段\n");DBG(" frame->can_id=0x%x\n", frame->can_id);char *p=(char*)&(frame->can_id);for(i=0;i<4;i++){DBG(" p=%x\n",*p);p++;}DBG(" frame->can_dlc=%d\n", frame->can_dlc);for(i=0;i<8;i++){DBG(" frame->data[%d]=%x\n",i,frame->data[i]);}    priv->net->stats.rx_packets++;    priv->net->stats.rx_bytes += frame->can_dlc;DBG("打印skb里的数据\n");for(i=0;i<20;i++){DBG("skb->data[%d]=%x\n",i,skb->data[i]);}    netif_rx_ni(skb);}static void mcp251x_hw_sleep(struct spi_device *spi){//    DBG("mcp251x_hw_sleep\n");    mcp251x_write_reg(spi, CANCTRL, CANCTRL_REQOP_SLEEP);}static netdev_tx_t mcp251x_hard_start_xmit(struct sk_buff *skb,                       struct net_device *net){    struct mcp251x_priv *priv = netdev_priv(net);    struct spi_device *spi = priv->spi;DBG("从应用层收到发送命令\n");    if (priv->tx_skb || priv->tx_len) {        dev_warn(&spi->dev, "hard_xmit called while tx busy\n");        return NETDEV_TX_BUSY;    }    if (can_dropped_invalid_skb(net, skb))        return NETDEV_TX_OK;    netif_stop_queue(net);    priv->tx_skb = skb;DBG("要发送的数据是skb\n");DBG("启动发送队列\n");    queue_work(priv->wq, &priv->tx_work);    return NETDEV_TX_OK;}static int mcp251x_do_set_mode(struct net_device *net, enum can_mode mode){    struct mcp251x_priv *priv = netdev_priv(net);         //        DBG("mcp251x_do_set_mode\n");    switch (mode) {    case CAN_MODE_START:        mcp251x_clean(net);        /* We have to delay work since SPI I/O may sleep */        priv->can.state = CAN_STATE_ERROR_ACTIVE;        priv->restart_tx = 1;        if (priv->can.restart_ms == 0)            priv->after_suspend = AFTER_SUSPEND_RESTART;        queue_work(priv->wq, &priv->restart_work);        break;    default:        return -EOPNOTSUPP;    }    return 0;}static int mcp251x_set_normal_mode(struct spi_device *spi){    struct mcp251x_priv *priv = dev_get_drvdata(&spi->dev);    unsigned long timeout;//     DBG("mcp251x_set_normal_mode\n");    /* Enable interrupts */        intset=CANINTE_ERRIE | CANINTE_TX2IE | CANINTE_TX1IE | //CANINTF_MERRF |              CANINTE_TX0IE | CANINTE_RX1IE | CANINTE_RX0IE;    mcp251x_write_reg(spi, CANINTE,intset);    if (priv->can.ctrlmode & CAN_CTRLMODE_LOOPBACK) {        /* Put device into loopback mode */        mcp251x_write_reg(spi, CANCTRL, CANCTRL_REQOP_LOOPBACK);    } else if (priv->can.ctrlmode & CAN_CTRLMODE_LISTENONLY) {        /* Put device into listen-only mode */        mcp251x_write_reg(spi, CANCTRL, CANCTRL_REQOP_LISTEN_ONLY);    } else {        /* Put device into normal mode */        mcp251x_write_reg(spi, CANCTRL, CANCTRL_REQOP_NORMAL);        /* Wait for the device to enter normal mode */        timeout = jiffies + HZ;        while (mcp251x_read_reg(spi, CANSTAT) & CANCTRL_REQOP_MASK) {            schedule();            if (time_after(jiffies, timeout)) {                dev_err(&spi->dev, "MCP251x didn't"                    " enter in normal mode\n");                return -EBUSY;            }        }    }    priv->can.state = CAN_STATE_ERROR_ACTIVE;    return 0;}static int mcp251x_do_set_bittiming(struct net_device *net){    struct mcp251x_priv *priv = netdev_priv(net);    struct can_bittiming *bt = &priv->can.bittiming;    struct spi_device *spi = priv->spi;//    DBG("mcp251x_do_set_bittiming\n");    mcp251x_write_reg(spi, CNF1, ((bt->sjw - 1) << CNF1_SJW_SHIFT) |              (bt->brp - 1));    mcp251x_write_reg(spi, CNF2, CNF2_BTLMODE |              (priv->can.ctrlmode & CAN_CTRLMODE_3_SAMPLES ?               CNF2_SAM : 0) |              ((bt->phase_seg1 - 1) << CNF2_PS1_SHIFT) |              (bt->prop_seg - 1));    mcp251x_write_bits(spi, CNF3, CNF3_PHSEG2_MASK,               (bt->phase_seg2 - 1));    dev_info(&spi->dev, "CNF: 0x%02x 0x%02x 0x%02x\n",         mcp251x_read_reg(spi, CNF1),         mcp251x_read_reg(spi, CNF2),         mcp251x_read_reg(spi, CNF3));    return 0;}static int mcp251x_setup(struct net_device *net, struct mcp251x_priv *priv,             struct spi_device *spi){    mcp251x_do_set_bittiming(net);//    DBG("mcp251x_setup\n");    mcp251x_write_reg(spi, RXBCTRL(0),              RXBCTRL_BUKT | RXBCTRL_RXM0 | RXBCTRL_RXM1);    mcp251x_write_reg(spi, RXBCTRL(1),              RXBCTRL_RXM0 | RXBCTRL_RXM1);    return 0;}static int mcp251x_hw_reset(struct spi_device *spi){    struct mcp251x_priv *priv = dev_get_drvdata(&spi->dev);    int ret;    unsigned long timeout;//    DBG("mcp251x_hw_reset\n");    priv->spi_tx_buf[0] = INSTRUCTION_RESET;    ret = spi_write(spi, priv->spi_tx_buf, 1);    if (ret) {        dev_err(&spi->dev, "reset failed: ret = %d\n", ret);        return -EIO;    }    /* Wait for reset to finish */    timeout = jiffies + HZ;    mdelay(10);    while ((mcp251x_read_reg(spi, CANSTAT) & CANCTRL_REQOP_MASK)           != CANCTRL_REQOP_CONF) {        schedule();        if (time_after(jiffies, timeout)) {            dev_err(&spi->dev, "MCP251x didn't"                " enter in conf mode after reset\n");            return -EBUSY;        }    }    return 0;}static int mcp251x_hw_probe(struct spi_device *spi){    int st1, st2;//    DBG("mcp251x_hw_probe\n");    mcp251x_hw_reset(spi);    /*     * Please note that these are "magic values" based on after     * reset defaults taken from data sheet which allows us to see     * if we really have a chip on the bus (we avoid common all     * zeroes or all ones situations)     */    st1 = mcp251x_read_reg(spi, CANSTAT) & 0xEE;    st2 = mcp251x_read_reg(spi, CANCTRL) & 0x17;    dev_dbg(&spi->dev, "CANSTAT 0x%02x CANCTRL 0x%02x\n", st1, st2);    /* Check for power up default values */    return (st1 == 0x80 && st2 == 0x07) ? 1 : 0;}static void mcp251x_open_clean(struct net_device *net){    struct mcp251x_priv *priv = netdev_priv(net);    struct spi_device *spi = priv->spi;    struct mcp251x_platform_data *pdata = spi->dev.platform_data;        DBG("mcp251x_open_clean\n");    free_irq(spi->irq, priv);    mcp251x_hw_sleep(spi);    if (pdata->transceiver_enable)        pdata->transceiver_enable(0);    close_candev(net);}static int mcp251x_stop(struct net_device *net){    struct mcp251x_priv *priv = netdev_priv(net);    struct spi_device *spi = priv->spi;    struct mcp251x_platform_data *pdata = spi->dev.platform_data;     DBG("mcp251x_stop\n");    close_candev(net);    priv->force_quit = 1;          free_irq(spi->irq, priv);    destroy_workqueue(priv->wq);    priv->wq = NULL;//        del_timer(&check_timer);  //删除定时器    mutex_lock(&priv->mcp_lock);    /* Disable and clear pending interrupts */    mcp251x_write_reg(spi, CANINTE, 0x00);    mcp251x_write_reg(spi, CANINTF, 0x00);    mcp251x_write_reg(spi, TXBCTRL(0), 0);    mcp251x_clean(net);    mcp251x_hw_sleep(spi);    if (pdata->transceiver_enable)        pdata->transceiver_enable(0);    priv->can.state = CAN_STATE_STOPPED;    mutex_unlock(&priv->mcp_lock);    return 0;}static void mcp251x_error_skb(struct net_device *net, int can_id, int data1){    struct sk_buff *skb;    struct can_frame *frame;     DBG("mcp251x_error_skb\n");    skb = alloc_can_err_skb(net, &frame);    if (skb) {        frame->can_id |= can_id;        frame->data[1] = data1;        netif_rx_ni(skb);    } else {        dev_err(&net->dev,            "cannot allocate error skb\n");    }}static void mcp251x_tx_work_handler(struct work_struct *ws){DBG("进入发送队列\n");    struct mcp251x_priv *priv = container_of(ws, struct mcp251x_priv,                         tx_work);    struct spi_device *spi = priv->spi;    struct net_device *net = priv->net;    struct can_frame *frame;    mutex_lock(&priv->mcp_lock);    if (priv->tx_skb) {        if (priv->can.state == CAN_STATE_BUS_OFF) {            mcp251x_clean(net);        } else {int i;DBG("打印skb里的数据\n");for(i=0;i<20;i++){DBG("priv->tx_skb->data[%d]=%x\n",i,priv->tx_skb->data[i]);}//将skb里的数据给can_frame以便组织发送            frame = (struct can_frame *)priv->tx_skb->data;DBG("打印can_frame的字段\n");DBG(" frame->can_id=0x%x\n", frame->can_id);char *p=(char*)&(frame->can_id);for(i=0;i<4;i++){DBG(" p=%x\n",*p);p++;}DBG(" frame->can_dlc=%d\n", frame->can_dlc);for(i=0;i<8;i++){DBG(" frame->data[%d]=%x\n",i,frame->data[i]);}            if (frame->can_dlc > CAN_FRAME_MAX_DATA_LEN)                frame->can_dlc = CAN_FRAME_MAX_DATA_LEN;//发送            mcp251x_hw_tx(spi, frame, 0);            priv->tx_len = 1 + frame->can_dlc;            can_put_echo_skb(priv->tx_skb, net, 0);            priv->tx_skb = NULL;        }    }    mutex_unlock(&priv->mcp_lock);}static void mcp251x_restart_work_handler(struct work_struct *ws){    struct mcp251x_priv *priv = container_of(ws, struct mcp251x_priv,                         restart_work);    struct spi_device *spi = priv->spi;    struct net_device *net = priv->net;    DBG("mcp251x_restart_work_handler\n");    mutex_lock(&priv->mcp_lock);    if (priv->after_suspend) {        mdelay(10);        mcp251x_hw_reset(spi);        mcp251x_setup(net, priv, spi);        if (priv->after_suspend & AFTER_SUSPEND_RESTART) {            mcp251x_set_normal_mode(spi);        } else if (priv->after_suspend & AFTER_SUSPEND_UP) {            netif_device_attach(net);            mcp251x_clean(net);            mcp251x_set_normal_mode(spi);            netif_wake_queue(net);        } else {            mcp251x_hw_sleep(spi);        }        priv->after_suspend = 0;        priv->force_quit = 0;    }    if (priv->restart_tx) {        priv->restart_tx = 0;        mcp251x_write_reg(spi, TXBCTRL(0), 0);        mcp251x_clean(net);        netif_wake_queue(net);        mcp251x_error_skb(net, CAN_ERR_RESTARTED, 0);    }    mutex_unlock(&priv->mcp_lock);}/*static void check_timer_callback(unsigned long arg){    //DBG("timer clean CANINTF %X\n",arg);    //int pin=gpio_get_value(S3C64XX_GPL(8)); //   int pin=gpio_get_value(S3C64XX_GPN(5));    int pin=gpio_get_value(S3C64XX_GPL(8));//    DBG("timer pin=%d \n",pin);    if(pin==0)    {//        struct mcp251x_priv *priv=(struct mcp251x_priv *)arg;//        schedule_work(&(priv->irq_work));         DBG("timer schedule work\n");    }    mod_timer(&check_timer,jiffies+8);        //修改定时器}*/static irqreturn_t mcp251x_can_irq(int irq, void *dev_id){DBG("有中断产生\n");       struct mcp251x_priv *priv = dev_id;//       struct spi_device *spi = priv->spi;      // int pin=gpio_get_value(S3C64XX_GPL(8));      // DBG("pin=%d \n",pin); //DBG("before disable_irq_nosync(irq);\n");        disable_irq_nosync(irq);    //disable_irq(irq);//DBG("after disable_irq_nosync(irq);\n");       //s3c_gpio_cfgpin(S3C64XX_GPL(8), S3C_GPIO_INPUT);  //关中断，为什么disable_irq死机       //while(S3C_GPIO_INPUT!=s3c_gpio_getcfg(S3C64XX_GPL(8)));       //schedule_work(&(priv->irq_work));        if (!work_pending(&priv->irq_work))        queue_work(priv->wq, &priv->irq_work);          //enable_irq(irq);       return IRQ_HANDLED;}/*static irqreturn_t mcp251x_can_irq(int irq, void *dev_id){DBG("mcp251x_can_irq\n");       struct mcp251x_priv *priv = dev_id;//       struct spi_device *spi = priv->spi;      // int pin=gpio_get_value(S3C64XX_GPL(8));      // DBG("pin=%d \n",pin);         //disable_irq_nosync(irq);       s3c_gpio_cfgpin(S3C64XX_GPL(8), S3C_GPIO_INPUT);  //关中断，为什么disable_irq死机       while(S3C_GPIO_INPUT!=s3c_gpio_getcfg(S3C64XX_GPL(8)));       //schedule_work(&(priv->irq_work));        if (!work_pending(&priv->irq_work))        queue_work(priv->wq, &priv->irq_work);             return IRQ_HANDLED;}*/void can_irq_work(struct work_struct *ws){DBG("进入中断下半部\n");     struct mcp251x_priv *priv = container_of(ws, struct mcp251x_priv,                         irq_work);     struct spi_device *spi = priv->spi;     struct net_device *net = priv->net;    mutex_lock(&priv->mcp_lock);        //mcp251x_write_reg(spi, CANINTE, (intset & (~ ( CANINTE_TX2IE) )));    while (!priv->force_quit) {        enum can_state new_state;        u8 intf, eflag;              u8 clear_intf = 0;        int can_id = 0, data1 = 0;                       mcp251x_read_2regs(spi, CANINTF, &intf, &eflag);//读取中断标志寄存器，用于判断是什么中断                DBG("中断标志=0x%x\n",intf);                //mcp251x_write_bits(spi, CANINTF, intf, 0x00);                /* mask out flags we don't care about */        intf &= CANINTF_RX | CANINTF_TX | CANINTF_ERR ;//| CANINTF_MERRF;                if (intf & CANINTF_TX) {DBG("是发送完成中断: \n");            net->stats.tx_packets++;            net->stats.tx_bytes += priv->tx_len - 1;            if (priv->tx_len) {                can_get_echo_skb(net, 0);                priv->tx_len = 0;            }            netif_wake_queue(net);        }                /* receive buffer 1 */        if (intf & CANINTF_RX1IF) {DBG("是接收到数据中断: \n");DBG("receive buffer1有数据\n");            mcp251x_hw_rx(spi, 1);            /* the MCP2515 does this automatically */            if (mcp251x_is_2510(spi))                clear_intf |= CANINTF_RX1IF;        }                /* receive buffer 0 */        if (intf & CANINTF_RX0IF) {DBG("是接收到数据中断: \n");DBG("receive buffer0有数据\n");            mcp251x_hw_rx(spi, 0);            /*             * Free one buffer ASAP             * (The MCP2515 does this automatically.)             */            if (mcp251x_is_2510(spi))                mcp251x_write_bits(spi, CANINTF, CANINTF_RX0IF, 0x00);        }           /* any error or tx interrupt we need to clear? */        if (intf & (CANINTF_ERR | CANINTF_TX))            clear_intf |= intf & (CANINTF_ERR | CANINTF_TX);        if (clear_intf)            mcp251x_write_bits(spi, CANINTF, clear_intf, 0x00);        if (eflag)            mcp251x_write_bits(spi, EFLG, eflag, 0x00);                       /* Update can state */        if (eflag & EFLG_TXBO) {            new_state = CAN_STATE_BUS_OFF;            can_id |= CAN_ERR_BUSOFF;        } else if (eflag & EFLG_TXEP) {            new_state = CAN_STATE_ERROR_PASSIVE;            can_id |= CAN_ERR_CRTL;            data1 |= CAN_ERR_CRTL_TX_PASSIVE;        } else if (eflag & EFLG_RXEP) {            new_state = CAN_STATE_ERROR_PASSIVE;            can_id |= CAN_ERR_CRTL;            data1 |= CAN_ERR_CRTL_RX_PASSIVE;        } else if (eflag & EFLG_TXWAR) {            new_state = CAN_STATE_ERROR_WARNING;            can_id |= CAN_ERR_CRTL;            data1 |= CAN_ERR_CRTL_TX_WARNING;        } else if (eflag & EFLG_RXWAR) {            new_state = CAN_STATE_ERROR_WARNING;            can_id |= CAN_ERR_CRTL;            data1 |= CAN_ERR_CRTL_RX_WARNING;        } else {            new_state = CAN_STATE_ERROR_ACTIVE;        }        /* Update can state statistics */        switch (priv->can.state) {        case CAN_STATE_ERROR_ACTIVE:            if (new_state >= CAN_STATE_ERROR_WARNING &&                new_state <= CAN_STATE_BUS_OFF)                priv->can.can_stats.error_warning++;        case CAN_STATE_ERROR_WARNING:    /* fallthrough */            if (new_state >= CAN_STATE_ERROR_PASSIVE &&                new_state <= CAN_STATE_BUS_OFF)                priv->can.can_stats.error_passive++;            break;        default:            break;        }        priv->can.state = new_state;        if (intf & CANINTF_ERRIF) {            /* Handle overflow counters */            if (eflag & (EFLG_RX0OVR | EFLG_RX1OVR)) {                if (eflag & EFLG_RX0OVR) {                    net->stats.rx_over_errors++;                    net->stats.rx_errors++;                }                if (eflag & EFLG_RX1OVR) {                    net->stats.rx_over_errors++;                    net->stats.rx_errors++;                }                can_id |= CAN_ERR_CRTL;                data1 |= CAN_ERR_CRTL_RX_OVERFLOW;            }            mcp251x_error_skb(net, can_id, data1);        }        if (priv->can.state == CAN_STATE_BUS_OFF) {            if (priv->can.restart_ms == 0) {                priv->force_quit = 1;                can_bus_off(net);                mcp251x_hw_sleep(spi);                break;            }        }                if (intf == 0)            break;        }        //mcp251x_write_reg(spi, CANINTE, intset);    mutex_unlock(&priv->mcp_lock);          enable_irq(spi->irq);        //s3c_gpio_cfgpin(S3C64XX_GPL(8), S3C_GPIO_SFN(3));    //开中断 }static int mcp251x_open(struct net_device *net){    struct mcp251x_priv *priv = netdev_priv(net);    struct spi_device *spi = priv->spi;    struct mcp251x_platform_data *pdata = spi->dev.platform_data;    int ret; //       DBG("mcp251x_open\n");DBG("mcp251x_open");    ret = open_candev(net);    if (ret) {        dev_err(&spi->dev, "unable to set initial baudrate!\n");        return ret;    }    mutex_lock(&priv->mcp_lock);    if (pdata->transceiver_enable)        pdata->transceiver_enable(1);    priv->force_quit = 0;    priv->tx_skb = NULL;    priv->tx_len = 0;/*    ret = request_threaded_irq(spi->irq, NULL, mcp251x_can_ist,          pdata->irq_flags ? pdata->irq_flags : IRQF_TRIGGER_FALLING, //IRQF_TRIGGER_LOW,  //           DEVICE_NAME, priv);*/    ret = request_irq(spi->irq, mcp251x_can_irq,              //IRQF_TRIGGER_FALLING,                          /*IRQF_DISABLED |*/ IRQF_TRIGGER_LOW , //note by song              DEVICE_NAME, priv);    INIT_WORK(&priv->irq_work,can_irq_work);    if (ret) {        dev_err(&spi->dev, "failed to acquire irq %d\n", spi->irq);        if (pdata->transceiver_enable)            pdata->transceiver_enable(0);        close_candev(net);        goto open_unlock;    }//    init_timer(&check_timer);   //初始化定时器//        check_timer.expires=jiffies+HZ;//        check_timer.function=&check_timer_callback;//        check_timer.data=(long)priv;        //add_timer(&check_timer);        //添加定时器*/    priv->wq = create_freezable_workqueue("mcp251x_wq");        //priv->wq = create_freezeable_workqueue("mcp251x_wq");    INIT_WORK(&priv->tx_work, mcp251x_tx_work_handler);    INIT_WORK(&priv->restart_work, mcp251x_restart_work_handler);    ret = mcp251x_hw_reset(spi);    if (ret) {        mcp251x_open_clean(net);        goto open_unlock;    }    ret = mcp251x_setup(net, priv, spi);    if (ret) {        mcp251x_open_clean(net);        goto open_unlock;    }    ret = mcp251x_set_normal_mode(spi);    if (ret) {        mcp251x_open_clean(net);        goto open_unlock;    }    netif_wake_queue(net);open_unlock:    mutex_unlock(&priv->mcp_lock);    return ret;}static const struct net_device_ops mcp251x_netdev_ops = {    .ndo_open = mcp251x_open,    .ndo_stop = mcp251x_stop,    .ndo_start_xmit = mcp251x_hard_start_xmit,};static int __devinit mcp251x_can_probe(struct spi_device *spi){    struct net_device *net;    struct mcp251x_priv *priv;    struct mcp251x_platform_data *pdata = spi->dev.platform_data;    int ret = -ENODEV;    DBG("@@@@@@@@@@@@@@@@@@@@\n");    DBG("mcp251x_can_probe \n");    DBG("@@@@@@@@@@@@@@@@@@@@\n");    if (!pdata)        /* Platform data is required for osc freq */        goto error_out;    /* Allocate can/net device */    net = alloc_candev(sizeof(struct mcp251x_priv), TX_ECHO_SKB_MAX);    if (!net) {        ret = -ENOMEM;        goto error_alloc;    }    net->netdev_ops = &mcp251x_netdev_ops;    net->flags |= IFF_ECHO;    priv = netdev_priv(net);    priv->can.bittiming_const = &mcp251x_bittiming_const;    priv->can.do_set_mode = mcp251x_do_set_mode;    priv->can.clock.freq = pdata->oscillator_frequency / 2;    priv->can.ctrlmode_supported = CAN_CTRLMODE_3_SAMPLES |        CAN_CTRLMODE_LOOPBACK | CAN_CTRLMODE_LISTENONLY;    priv->model = spi_get_device_id(spi)->driver_data;    priv->net = net;    dev_set_drvdata(&spi->dev, priv);    priv->spi = spi;    mutex_init(&priv->mcp_lock);        /* If requested, allocate DMA buffers */    if (mcp251x_enable_dma) {        spi->dev.coherent_dma_mask = ~0;        /*         * Minimum coherent DMA allocation is PAGE_SIZE, so allocate         * that much and share it between Tx and Rx DMA buffers.         */        priv->spi_tx_buf = dma_alloc_coherent(&spi->dev,                              PAGE_SIZE,                              &priv->spi_tx_dma,                              GFP_DMA);        if (priv->spi_tx_buf) {            priv->spi_rx_buf = (u8 *)(priv->spi_tx_buf +                          (PAGE_SIZE / 2));            priv->spi_rx_dma = (dma_addr_t)(priv->spi_tx_dma +                            (PAGE_SIZE / 2));        } else {            /* Fall back to non-DMA */            mcp251x_enable_dma = 0;        }    }    /* Allocate non-DMA buffers */    if (!mcp251x_enable_dma) {        priv->spi_tx_buf = kmalloc(SPI_TRANSFER_BUF_LEN, GFP_KERNEL);        if (!priv->spi_tx_buf) {            ret = -ENOMEM;            goto error_tx_buf;        }        priv->spi_rx_buf = kmalloc(SPI_TRANSFER_BUF_LEN, GFP_KERNEL);        if (!priv->spi_rx_buf) {            ret = -ENOMEM;            goto error_rx_buf;        }    }    if (pdata->power_enable)        pdata->power_enable(1);    /* Call out to platform specific setup */    if (pdata->board_specific_setup)        pdata->board_specific_setup(spi);    SET_NETDEV_DEV(net, &spi->dev);    /* Configure the SPI bus */    spi->mode = SPI_MODE_0;    spi->bits_per_word = 8;    spi_setup(spi);    /* Here is OK to not lock the MCP, no one knows about it yet */    if (!mcp251x_hw_probe(spi)) {        dev_info(&spi->dev, "Probe failed\n");        goto error_probe;    }    mcp251x_hw_sleep(spi);    if (pdata->transceiver_enable)        pdata->transceiver_enable(0);    ret = register_candev(net);    DBG("@@@@@@@@@@@@@@@@@@@@\n");    DBG("register_candev ret = %d\n",ret);    DBG("@@@@@@@@@@@@@@@@@@@@\n");    if (!ret) {        dev_info(&spi->dev, "probed\n");        return ret;    }error_probe:    if (!mcp251x_enable_dma)        kfree(priv->spi_rx_buf);error_rx_buf:    if (!mcp251x_enable_dma)        kfree(priv->spi_tx_buf);error_tx_buf:    free_candev(net);    if (mcp251x_enable_dma)        dma_free_coherent(&spi->dev, PAGE_SIZE,                  priv->spi_tx_buf, priv->spi_tx_dma);error_alloc:    if (pdata->power_enable)        pdata->power_enable(0);    dev_err(&spi->dev, "probe failed\n");error_out:    return ret;}static int __devexit mcp251x_can_remove(struct spi_device *spi){    struct mcp251x_platform_data *pdata = spi->dev.platform_data;    struct mcp251x_priv *priv = dev_get_drvdata(&spi->dev);    struct net_device *net = priv->net;    DBG("mcp251x_can_remove\n");    unregister_candev(net);    free_candev(net);    if (mcp251x_enable_dma) {        dma_free_coherent(&spi->dev, PAGE_SIZE,                  priv->spi_tx_buf, priv->spi_tx_dma);    } else {        kfree(priv->spi_tx_buf);        kfree(priv->spi_rx_buf);    }    if (pdata->power_enable)        pdata->power_enable(0);    return 0;}#ifdef CONFIG_PMstatic int mcp251x_can_suspend(struct spi_device *spi, pm_message_t state){    struct mcp251x_platform_data *pdata = spi->dev.platform_data;    struct mcp251x_priv *priv = dev_get_drvdata(&spi->dev);    struct net_device *net = priv->net;    DBG("mcp251x_can_suspend\n");    priv->force_quit = 1;    disable_irq(spi->irq);    /*     * Note: at this point neither IST nor workqueues are running.     * open/stop cannot be called anyway so locking is not needed     */    if (netif_running(net)) {        netif_device_detach(net);        mcp251x_hw_sleep(spi);        if (pdata->transceiver_enable)            pdata->transceiver_enable(0);        priv->after_suspend = AFTER_SUSPEND_UP;    } else {        priv->after_suspend = AFTER_SUSPEND_DOWN;    }    if (pdata->power_enable) {        pdata->power_enable(0);        priv->after_suspend |= AFTER_SUSPEND_POWER;    }    return 0;}static int mcp251x_can_resume(struct spi_device *spi){        DBG("mcp251x_can_resume\n");    struct mcp251x_platform_data *pdata = spi->dev.platform_data;    struct mcp251x_priv *priv = dev_get_drvdata(&spi->dev);    if (priv->after_suspend & AFTER_SUSPEND_POWER) {        pdata->power_enable(1);        queue_work(priv->wq, &priv->restart_work);    } else {        if (priv->after_suspend & AFTER_SUSPEND_UP) {            if (pdata->transceiver_enable)                pdata->transceiver_enable(1);            queue_work(priv->wq, &priv->restart_work);        } else {            priv->after_suspend = 0;        }    }    priv->force_quit = 0;    enable_irq(spi->irq);    return 0;}#else#define mcp251x_can_suspend NULL#define mcp251x_can_resume NULL#endifstatic const struct spi_device_id mcp251x_id_table[] = {    { "mcp2510",    CAN_MCP251X_MCP2510 },    { "mcp2515",    CAN_MCP251X_MCP2515 },    { },};MODULE_DEVICE_TABLE(spi, mcp251x_id_table);static struct spi_driver mcp251x_can_driver = {    .driver = {        .name = DEVICE_NAME,        .bus = &spi_bus_type,        .owner = THIS_MODULE,    },    .id_table = mcp251x_id_table,    .probe = mcp251x_can_probe,    .remove = __devexit_p(mcp251x_can_remove),    .suspend = mcp251x_can_suspend,    .resume = mcp251x_can_resume,};static int __init mcp251x_can_init(void){DBG("init\n");    return spi_register_driver(&mcp251x_can_driver);}static void __exit mcp251x_can_exit(void){DBG("exit\n");    spi_unregister_driver(&mcp251x_can_driver);}module_init(mcp251x_can_init);module_exit(mcp251x_can_exit);MODULE_AUTHOR("Chris Elston <[e-mail]>, "          "Christian Pellegrin <[e-mail]>");MODULE_DESCRIPTION("Microchip 251x CAN driver");MODULE_LICENSE("GPL v2");

******************************************************************
几个疑点分析----以下讨论适用于te6410
中断注册

static inline int __must_checkrequest_irq(unsigned int irq, irq_handler_t handler, unsigned long flags,    const char *name, void *dev){return request_threaded_irq(irq, handler, NULL, flags, name, dev);}

原来他调用了request_threaded_irq(),并将中断处理函数(上半部)handler作为参数传递过去。追踪到request_threaded_irq，如下

int request_threaded_irq(unsigned int irq, irq_handler_t handler, irq_handler_t thread_fn, unsigned long irqflags, const char *devname, void *dev_id)

其中要注意的两个参数，
irq_handler_t   handler，中断处理函数上半部
irq_handler_t   thread_fn，中断线程化，这样直接实现了中断处理函数的下半部，不必自己再去使用工作队列实现下半部了
/*
附工作队列的实现
创建工作队列，并加入到一个工作者线程里让其去执行。这个工作者线程可以使内核现成的，也可以使自己心创建的。
创建一个工作队列work_struct，使用DECLARE_WORK静态创建一个工作队列，参数包括队列名称和队列函数，也可使用INIT_WORK动态创建。
创建一个新的工作者线程workqueue_struct,使用create_workqueue，返回值是工作者线程指针。

将工作队列放到指定的工作者线程中去执行，
int queue_work(struct workqueue_struct *wq, struct work_struct *work)
将工作队列放到系统已有的events工作者线程中去执行，直接调用sheldule_work(&work)即可。

工作者线程是一个内核线程，运行在进程上下文。
工作者线程被唤醒时，会依次执行它里面的工作队列----组成了一个链表。

*/

搜索2.6.32.2源码，只发现一个同时使用了这两个参数的例子Broadcom B43 wireless driver,位于dribers/net/wireless/b43/main.c

err = request_threaded_irq(dev->dev->irq, b43_interrupt_handler,   b43_interrupt_thread_handler,   IRQF_SHARED, KBUILD_MODNAME, dev);

其在中断上半部b43_interrupt_handler里禁止中断，在中断下半部b43_interrupt_thread_handler里批量读取数据然后重新使能中断(如果要清除中断标志位，则在使能之前先清除一下)。

其余的例子几乎都只使用了一个参数thread_fn，而handler置为NULL,比如
mcs5000_ts.c - Touchscreen driver for MELFAS MCS-5000 controller

ret = request_threaded_irq(client->irq, NULL, mcs5000_ts_interrupt,IRQF_TRIGGER_LOW | IRQF_ONESHOT, "mcs5000_ts", data);

又如本文要讨论的 mcp251x.c - CAN bus driver for Microchip 251x CAN Controller with SPI Interface

ret = request_threaded_irq(spi->irq, NULL, mcp251x_can_ist,  IRQF_TRIGGER_FALLING, DEVICE_NAME, priv);

中断触发
使用IRQF_TRIGGER_FALLING作为中断触发的条件。而mcp2515则是只要有数据发送完成(发给can总线)或有新的数据到来(来自can总线)就会置int引脚低电平，此脚接到0k6410的eint16，向ok6410发送中断中断信号。

MCP2515有八个中断源。CANINTE寄存器包含了使能各中断源的中断使能位。 CANINTF 寄存器包含了各中断源的中断标志位。当发生中断时，INT 引脚将被MCP2515拉为低电平，并保持低电平状态直至MCU清除中断。中断只有在引起相应中断的条件消失后，才会被清除。mcp2515会自动清除中断吗？说明书上没写自动清除。mcp251x.c中却认为可以自动清除？

如果使用低电平触发，则须存在中断上半部，在上半部里面先disable此中断，然后在下半部里面传输完数据之后再enable此中断。
如果不在上半部disable此中断，则由于低电平一直存在，就会一直触发中断，从而一直执行中断上半部，(下半部根本就没机会执行到)，造成死机。

如果使用低电平触发，如果中断上半部函数指针设为NULL，那么即使在中断下半部执行disable此中断，也会造成死机。
因为中断发生时，不会立即执行下半部函数，所以有可能没及时禁掉此中断，造成中断(此时仍然低电平)继续触发而使下半部线程大量重复的创建(或许)造成死机。

如果使用下降沿触发，可以不存在上半部，即上半部函数指针可设为NULL，在下半部中可以先disable此中断，然后读取数据再清除中断标志位

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refer to
lkd2
http://blog.csdn.net/zhangjie201412/article/details/7067448