spi 外设驱动(spi_driver)

spi驱动模型和i2c的类似，都按照主机外设分离来设计的。但我觉得比i2c的要简明好多。
上文配置的spi驱动最外层是platform总线然后是spi总线然后是字符设备。
spi驱动模型分为
spi主控制器驱动，对应结构体spi_master-spi_s3c24xx.c。控制怎么发。
spi外设驱动，对应结构体spi_driver-----spidev.c。实现与用户的接口。
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对于te6410,linux2.6.36.2  2012-6-10 
在板子文件mach-smdk6410.c中注册平台设备，
在spi_s3c64xx.c中使用platform_driver_probe(platform_driver_register)注册平台驱动，
在平台驱动的probe函数中，注册使用spi_register_master注册spi主机控制器驱动，实现操作spi寄存器。
在spidev.c中使用spi_register_driver注册spi外设驱动。并注册字符设备实现与用户空间的接口。或者不使用字符设备也行，比如mcp2515没有使用字符设备，而是按照net_device的思路来实现用户接口的。

由于平台设备写进了板子文件，所以在系统启动时会自动注册这个平台设备及将其挂在平台总线。由于平台驱动也编译进了内核，所以也会自动注册即也挂在了平台总线。平台核心会匹配两者，
成功后，调用平台驱动的probe函数来注册spi主机控制器驱动此时会将主机控制器驱动挂在spi总线。在spi外设驱动insmod进内核时即也挂上了spi总线，spi核心会匹配两者，
成功后，调用spi外设驱动的probe函数实现真正的用户接口比如cdev，net_device。

而在spi外设驱动实现的read,write等函数，最终调用的是匹配的spi主机控制器驱动的transfer()

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关于spi_driver和spi_device的匹配：
spi_driver中name字段
static struct spi_driver spidev_spi_driver = {
    .driver = {
        .name =        "spidev",
        .owner =    THIS_MODULE,
    },
...
}
和mach-smdk6410.c中的modalias字段
static struct spi_board_info s3c2410_spi0_board[] = {  
        [0] = {  
                 .modalias = "spidev", 
                .bus_num        = 0,    
                .chip_select        = 0, 
                .max_speed_hz         = 500*1000,  
        },  
}; 
要一致才行。
如果使用id_table来匹配则id_table中的项目要与spi_board_info中的modalias 匹配( 假如.modalias = "mcp2515", )，则在mcp251x.c中

static const struct spi_device_id mcp251x_id_table[] = {
    { "mcp2510",    CAN_MCP251X_MCP2510 },
    { "mcp2515",    CAN_MCP251X_MCP2515 },//必须的
    { },
};

MODULE_DEVICE_TABLE(spi, mcp251x_id_table);

static struct spi_driver mcp251x_can_driver = {
    .driver = {
        .name = "mcp2515",//无关,可以不是mcp2515
        .bus = &spi_bus_type,
        .owner = THIS_MODULE,
    },

    .id_table = mcp251x_id_table,
}

匹配原理
spi_master注册过程中会扫描arch/.../mach-*/board-*.c 中调用spi_register_board_info注册的信息，为每一个与本总线编号相同的信息建立一个spi_device。
根据Linux内核的驱动模型，注册在同一总线下的驱动和设备会进行匹配。spi_bus_type总线匹配的依据是名字。这样当自己编写的spi_driver和spi_device同名的时候，
spi_driver的probe方法就会被调用。spi_driver就能看到与自己匹配的spi_device了。
http://blog.csdn.net/yuanlulu/article/details/6318165

如果有idtable的话，就匹配idtable里各个项目的name,这样就可以支持多个name了,如源码
spi.c

static int spi_match_device(struct device *dev, struct device_driver *drv){const struct spi_device*spi = to_spi_device(dev);const struct spi_driver*sdrv = to_spi_driver(drv);/* Attempt an OF style match */if (of_driver_match_device(dev, drv))return 1;if (sdrv->id_table)return !!spi_match_id(sdrv->id_table, spi);return strcmp(spi->modalias, drv->name) == 0;}static const struct spi_device_id *spi_match_id(const struct spi_device_id *id,                        const struct spi_device *sdev){    while (id->name[0]) {        if (!strcmp(sdev->modalias, id->name))            return id;        id++;    }    return NULL;}

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在spidev.c实现了spi的字符设备驱动

static struct spi_driver spidev_spi_driver = {.driver = {.name ="spidev",.owner =THIS_MODULE,},.probe =spidev_probe,.remove =__devexit_p(spidev_remove),/* NOTE:  suspend/resume methods are not necessary here. * We don't do anything except pass the requests to/from * the underlying controller.  The refrigerator handles * most issues; the controller driver handles the rest. */};static int __init spidev_init(void){int status;/* Claim our 256 reserved device numbers.  Then register a class * that will key udev/mdev to add/remove /dev nodes.  Last, register * the driver which manages those device numbers. */BUILD_BUG_ON(N_SPI_MINORS > 256);status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);//注册字符设备，这个才是真的用户接口if (status < 0)return status;spidev_class = class_create(THIS_MODULE, "spidev");if (IS_ERR(spidev_class)) {unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);return PTR_ERR(spidev_class);}status = spi_register_driver(&spidev_spi_driver);//注册spi_driverif (status < 0) {class_destroy(spidev_class);unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);}return status;}static const struct file_operations spidev_fops = {.owner =THIS_MODULE,/* REVISIT switch to aio primitives, so that userspace * gets more complete API coverage.  It'll simplify things * too, except for the locking. */.write =spidev_write,.read =spidev_read,.unlocked_ioctl = spidev_ioctl,.open =spidev_open,.release =spidev_release,};static int __devinit spidev_probe(struct spi_device *spi){struct spidev_data*spidev;intstatus;unsigned longminor;/* Allocate driver data */spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);if (!spidev)return -ENOMEM;/* Initialize the driver data */spidev->spi = spi;spin_lock_init(&spidev->spi_lock);mutex_init(&spidev->buf_lock);INIT_LIST_HEAD(&spidev->device_entry);/* If we can allocate a minor number, hook up this device. * Reusing minors is fine so long as udev or mdev is working. */mutex_lock(&device_list_lock);minor = find_first_zero_bit(minors, N_SPI_MINORS);if (minor < N_SPI_MINORS) {struct device *dev;spidev->devt = MKDEV(SPIDEV_MAJOR, minor);dev = device_create(spidev_class, &spi->dev, spidev->devt,    spidev, "spidev%d.%d",    spi->master->bus_num, spi->chip_select);//创建设备文件status = IS_ERR(dev) ? PTR_ERR(dev) : 0;} else {dev_dbg(&spi->dev, "no minor number available!\n");status = -ENODEV;}if (status == 0) {set_bit(minor, minors);list_add(&spidev->device_entry, &device_list);}mutex_unlock(&device_list_lock);if (status == 0)spi_set_drvdata(spi, spidev);elsekfree(spidev);return status;}//spi读，调用spidev_sync_read--spidev_sync--spi_async,最后这个函数是spi核心提供的，这个函数最终会调用master的transfer函数直接操作硬件来传输数据。/* Read-only message with current device setup */static ssize_tspidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos){struct spidev_data*spidev;ssize_tstatus = 0;/* chipselect only toggles at start or end of operation */if (count > bufsiz)return -EMSGSIZE;spidev = filp->private_data;mutex_lock(&spidev->buf_lock);status = spidev_sync_read(spidev, count);if (status > 0) {unsigned longmissing;missing = copy_to_user(buf, spidev->buffer, status);if (missing == status)status = -EFAULT;elsestatus = status - missing;}mutex_unlock(&spidev->buf_lock);return status;}static inline ssize_tspidev_sync_read(struct spidev_data *spidev, size_t len){struct spi_transfert = {.rx_buf= spidev->buffer,.len= len,};struct spi_messagem;spi_message_init(&m);//初始化spi_message，spi_message_add_tail(&t, &m);return spidev_sync(spidev, &m);}static ssize_tspidev_sync(struct spidev_data *spidev, struct spi_message *message){DECLARE_COMPLETION_ONSTACK(done);int status;message->complete = spidev_complete;message->context = &done;spin_lock_irq(&spidev->spi_lock);if (spidev->spi == NULL)status = -ESHUTDOWN;elsestatus = spi_async(spidev->spi, message);//异步传输，如果是同步传输，则会阻塞一直到这个消息被处理完。spin_unlock_irq(&spidev->spi_lock);if (status == 0) {wait_for_completion(&done);status = message->status;if (status == 0)status = message->actual_length;}return status;}//spi写，调用spidev_sync_write--spidev_sync--spi_async,最后这个函数是spi核心提供的，这个函数最终会调用master的transfer函数直接操作硬件来传输数据。/* Write-only message with current device setup */static ssize_tspidev_write(struct file *filp, const char __user *buf,size_t count, loff_t *f_pos){struct spidev_data*spidev;ssize_tstatus = 0;unsigned longmissing;/* chipselect only toggles at start or end of operation */if (count > bufsiz)return -EMSGSIZE;spidev = filp->private_data;mutex_lock(&spidev->buf_lock);missing = copy_from_user(spidev->buffer, buf, count);if (missing == 0) {status = spidev_sync_write(spidev, count);} elsestatus = -EFAULT;mutex_unlock(&spidev->buf_lock);return status;}

http://blog.csdn.net/songqqnew/article/details/7037583