spi驅動模型和i2c的類似，都按照主機外設分離來設計的。但我覺得比i2c的要簡明好多。
上文配置的spi驅動最外層是platform總線然后是spi總線然后是字符設備。
spi驅動模型分為
spi主控制器驅動，對應結構體spi_master-spi_s3c24xx.c。控制怎么發。
spi外設驅動，對應結構體spi_driver-----spidev.c。實現與用戶的接口。
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對于te6410,linux2.6.36.2 ?2012-6-10?
在板子文件mach-smdk6410.c中注冊平臺設備，
在spi_s3c64xx.c中使用platform_driver_probe(platform_driver_register)注冊平臺驅動，
在平臺驅動的probe函數中，注冊使用spi_register_master注冊spi主機控制器驅動，實現操作spi寄存器。
在spidev.c中使用spi_register_driver注冊spi外設驅動。并注冊字符設備實現與用戶空間的接口。或者不使用字符設備也行，比如mcp2515沒有使用字符設備，而是按照net_device的思路來實現用戶接口的。

由于平臺設備寫進了板子文件，所以在系統啟動時會自動注冊這個平臺設備及將其掛在平臺總線。由于平臺驅動也編譯進了內核，所以也會自動注冊即也掛在了平臺總線。平臺核心會匹配兩者，
成功后，調用平臺驅動的probe函數來注冊spi主機控制器驅動此時會將主機控制器驅動掛在spi總線。在spi外設驅動insmod進內核時即也掛上了spi總線，spi核心會匹配兩者，
成功后，調用spi外設驅動的probe函數實現真正的用戶接口比如cdev，net_device。

而在spi外設驅動實現的read,write等函數，最終調用的是匹配的spi主機控制器驅動的transfer()

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關于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來匹配則id_table中的項目要與spi_board_info中的modalias 匹配( 假如.modalias = "mcp2515", )，則在mcp251x.c中

static const struct spi_device_id mcp251x_id_table[] = {
?? ?{ "mcp2510",?? ?CAN_MCP251X_MCP2510 },
?? ?{ "mcp2515",?? ?CAN_MCP251X_MCP2515 },//必須的
?? ?{ },
};

MODULE_DEVICE_TABLE(spi, mcp251x_id_table);

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

?? ?.id_table = mcp251x_id_table,
}

匹配原理
spi_master注冊過程中會掃描arch/.../mach-*/board-*.c 中調用spi_register_board_info注冊的信息，為每一個與本總線編號相同的信息建立一個spi_device。
根據Linux內核的驅動模型，注冊在同一總線下的驅動和設備會進行匹配。spi_bus_type總線匹配的依據是名字。這樣當自己編寫的spi_driver和spi_device同名的時候，
spi_driver的probe方法就會被調用。spi_driver就能看到與自己匹配的spi_device了。
http://blog.csdn.net/yuanlulu/article/details/6318165

如果有idtable的話，就匹配idtable里各個項目的name,這樣就可以支持多個name了,如源碼
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; }

***************************************************************************************
在spidev.c實現了spi的字符設備驅動
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);//注冊字符設備，這個才是真的用戶接口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);//注冊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;int status;unsigned long minor;/* 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);//創建設備文件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讀，調用spidev_sync_read--spidev_sync--spi_async,最后這個函數是spi核心提供的，這個函數最終會調用master的transfer函數直接操作硬件來傳輸數據。 /* Read-only message with current device setup */ static ssize_t spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos) {struct spidev_data *spidev;ssize_t status = 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 long missing;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_t spidev_sync_read(struct spidev_data *spidev, size_t len) {struct spi_transfer t = {.rx_buf = spidev->buffer,.len = len,};struct spi_message m;spi_message_init(&m);//初始化spi_message，spi_message_add_tail(&t, &m);return spidev_sync(spidev, &m); }static ssize_t spidev_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);//異步傳輸，如果是同步傳輸，則會阻塞一直到這個消息被處理完。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寫，調用spidev_sync_write--spidev_sync--spi_async,最后這個函數是spi核心提供的，這個函數最終會調用master的transfer函數直接操作硬件來傳輸數據。 /* Write-only message with current device setup */ static ssize_t spidev_write(struct file *filp, const char __user *buf,size_t count, loff_t *f_pos) {struct spidev_data *spidev;ssize_t status = 0;unsigned long missing;/* 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

轉載于:https://www.cnblogs.com/-song/archive/2011/12/03/3331907.html

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