Linux 2.6下SPI设备模型——–基于AT91RM9200分析Atmel公司的ARM AT系列，其SPI驱动在kernel 2.6.23里已经包含。如果你打了at91-patch补丁的话，则在内核配置时要小心。在Device Drivers—- > Character devices —- >取消选中SPI Driver(legacy) for at91rm9200 processor 。同时Device Drivers—- >SPI Support —- > 选中SPI Support ,Atmel SPI Controler,同时选中 User mode SPI device driver support 。SPI Driver(legacy) for at91rm9200 processor是保留选项，为了兼容以前版本。如果同时选中SPI Driver(legacy) for at91rm9200 processor，则在/sys里无法注册类spidev，也就无法将设备和驱动联系在一起。与现有atmel spi驱动发生冲突。各选项对应的编译情况如下：[*]SPI support —- Config_SPI 开启SPI功能[*]Debug support for SPI drivers —- config SPI_DEBUG 开启SPI debug调试—-SPI Master Controller Drivers —- depends on SPI_MASTER 生成spi.o<*>Atmel SPI Controller —- config SPI_ATMEL 生成atmel_spi.o<*>Bitbanging SPI master —- config SPI_BITBANG 生成spi_bitbang.o<*>AT91RM9200 Bitbang SPI Master —- CONFIG_SPI_AT91 spi_at91_bitbang.o—- SPI Protocol Masters —- depends on SPI_MASTER< >SPI EEPROMs from most vendors —- config SPI_AT25 生成at25.o<*>User mode SPI device driver support —- config SPI_SPIDEV 生成spidev.o总线注册SPI总线#spi.cstruct bus_type spi_bus_type = {.name = “spi”, // spi总线名称.dev_attrs = spi_dev_attrs,.match = spi_match_device,.uevent = spi_uevent,.suspend = spi_suspend,.resume = spi_resume,};spi总线将在sysfs/bus下显示。其bus_type 结构表示总线，它的定义在中，如下struct bus_type {const char * name;struct module * owner;struct kset subsys;struct kset drivers;struct kset devices;struct klist klist_devices;struct klist klist_drivers;struct blocking_notifier_head bus_notifier;struct bus_attribute * bus_attrs;struct device_attribute * dev_attrs;struct driver_attribute * drv_attrs;struct bus_attribute drivers_autoprobe_attr;struct bus_attribute drivers_probe_attr;int (*match)(struct device * dev, struct device_driver * drv);int (*uevent)(struct device *dev, char **envp,int num_envp, char *buffer, int buffer_size);int (*probe)(struct device * dev);int (*remove)(struct device * dev);void (*shutdown)(struct device * dev);int (*suspend)(struct device * dev, pm_message_t state);int (*suspend_late)(struct device * dev, pm_message_t state);int (*resume_early)(struct device * dev);int (*resume)(struct device * dev);unsigned int drivers_autoprobe:1;};其中，当一个总线上的新设备或者新驱动被添加时，*match 函数会被调用。如果指定的驱动程序能够处理指定的设备，该函数返回非零值。对于spi总线，我们必须调用bus_register(&spi_bus_type)进行注册。调用如果成功，SPI总线子系统将被添加到系统中，在sysfs的/sys/bus目录下可以看到。然后，我们就可以向这个总线添加设备了。代码见下：static int __init spi_init(void){int status;buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);if (!buf) {status = -ENOMEM;goto err0;}status = bus_register(&spi_bus_type);if (status < 0)goto err1;status = class_register(&spi_master_class);if (status < 0)goto err2;return 0;err2:bus_unregister(&spi_bus_type);err1:kfree(buf);buf = NULL;err0:return status;}设备spi设备的结构如下：#spi.hstruct spi_device {struct device dev;struct spi_master *master;u32 max_speed_hz;u8 chip_select;u8 mode;#define SPI_CPHA 0x01 /* clock phase */#define SPI_CPOL 0x02 /* clock polarity */#define SPI_MODE_0 (0|0) /* (original MicroWire) */#define SPI_MODE_1 (0|SPI_CPHA)#define SPI_MODE_2 (SPI_CPOL|0)#define SPI_MODE_3 (SPI_CPOL|SPI_CPHA)#define SPI_CS_HIGH 0x04 /* chipselect active high? */#define SPI_LSB_FIRST 0x08 /* per-word bits-on-wire */#define SPI_3WIRE 0x10 /* SI/SO signals shared */#define SPI_LOOP 0x20 /* loopback mode */u8 bits_per_word;int irq;void *controller_state;void *controller_data;const char *modalias;/** likely need more hooks for more protocol options affecting how* the controller talks to each chip, like:* – memory packing (12 bit samples into low bits, others zeroed)* – priority* – drop chipselect after each word* – chipselect delays* – …*/};device结构中包含了设备模型核心用来模拟系统的信息。spidev还有设备的其他信息，因此spi设备结构包含在spidev_data结构里。struct spidev_data {struct device dev;struct spi_device *spi;struct list_head device_entry;struct mutex buf_lock;unsigned users;u8 *buffer;};注册spi设备，#spidev.cstatic int spidev_probe(struct spi_device *spi){……status = device_register(&spidev->dev);……}完成这个调用之后，我们就可以在sysfs中看到它了。SPI设备驱动程序spi驱动程序结构如下：struct spi_driver {int (*probe)(struct spi_device *spi);int (*remove)(struct spi_device *spi);void (*shutdown)(struct spi_device *spi);int (*suspend)(struct spi_device *spi, pm_message_t mesg);int (*resume)(struct spi_device *spi);struct device_driver driver;};spi驱动程序注册函数如下：int spi_register_driver(struct spi_driver *sdrv){sdrv->driver.bus = &spi_bus_type;if (sdrv->probe)sdrv->driver.probe = spi_drv_probe;if (sdrv->remove)sdrv->driver.remove = spi_drv_remove;if (sdrv->shutdown)sdrv->driver.shutdown = spi_drv_shutdown;return driver_register(&sdrv->driver);}spidev的驱动名如下：static struct spi_driver spidev_spi = {.driver = {.name = “spidev”,.owner = THIS_MODULE,},.probe = spidev_probe,.remove = __devexit_p(spidev_remove),};一个spi_register_driver调用将spidev添加到系统中。一旦初始化完成，就可以在sysfs中看到驱动程序信息。类spidev类结构如下:static struct class spidev_class = {.name = “spidev”,.owner = THIS_MODULE,.dev_release = spidev_classdev_release,};AT91RM9200 SPIDEV初始化AT91RM9200的spi驱动，对于EK板，原先的SPI是用于dataflash的。其代码如下：static struct spi_board_info ek_spi_devices[] = {{ /* DataFlash chip */.modalias = “mtd_dataflash”,.chip_select = 0,.max_speed_hz = 15 * 1000 * 1000,}，我们需要将.modalias改成我们自己的spi设备名在spi设备初始化代码中，class_register(&spidev_class)注册类，spi_register_driver(&spidev_spi)注册spidev驱动。#drivers/spi/spidev.cstatic 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);if (status < 0)return status;status = class_register(&spidev_class);if (status < 0) {unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);return status;}status = spi_register_driver(&spidev_spi);if (status < 0) {class_unregister(&spidev_class);unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);}return status;}挂载/sysmount -t sysfs sysfs /sys可以看到有/sys/class/spidev/spidev0.0，表明设备已经挂载在总线上了，同时与驱动联系起来。使用mdev -s，可以在/dev下看到spidev0.0这个设备了。自此，spi设备驱动就可以工作了。测试程序：#include#include#include#include#include#include#include#include#include#includestatic int verbose;static void do_read(int fd, int len){unsigned char buf[32], *bp;int status;/* read at least 2 bytes, no more than 32 */if (len < 2)len = 2;else if (len > sizeof(buf))len = sizeof(buf);memset(buf, 0, sizeof buf);status = read(fd, buf, len);if (status < 0) {perror(“read”);return;}if (status != len) {fprintf(stderr, “short read/n”);return;}printf(“read(%2d, %2d): %02x %02x,”, len, status,buf[0], buf[1]);status -= 2;bp = buf + 2;while (status– > 0)printf(” %02x”, *bp++);printf(“/n”);}static void do_msg(int fd, int len){struct spi_ioc_transfer xfer[2];unsigned char buf[32], *bp;int status;memset(xfer, 0, sizeof xfer);memset(buf, 0, sizeof buf);if (len > sizeof buf)len = sizeof buf;buf[0] = 0xaa;xfer[0].tx_buf = (__u64) buf;xfer[0].len = 1;xfer[1].rx_buf = (__u64) buf;xfer[1].len = len;status = ioctl(fd, SPI_IOC_MESSAGE(2), xfer);if (status < 0) {perror(“SPI_IOC_MESSAGE”);return;}printf(“response(%2d, %2d): “, len, status);for (bp = buf; len; len–)printf(” %02x”, *bp++);printf(“/n”);}static void dumpstat(const char *name, int fd){__u8 mode, lsb, bits;__u32 speed;if (ioctl(fd, SPI_IOC_RD_MODE, &mode) < 0) {perror(“SPI rd_mode”);return;}if (ioctl(fd, SPI_IOC_RD_LSB_FIRST, &lsb) < 0) {perror(“SPI rd_lsb_fist”);return;}if (ioctl(fd, SPI_IOC_RD_BITS_PER_WORD, &bits) < 0) {perror(“SPI bits_per_word”);return;}if (ioctl(fd, SPI_IOC_RD_MAX_SPEED_HZ, &speed) < 0) {perror(“SPI max_speed_hz”);return;}printf(“%s: spi mode %d, %d bits %sper word, %d Hz max/n”,name, mode, bits, lsb ? “(lsb first) ” : “”, speed);}int main(int argc, char **argv){int c;int readcount = 0;int msglen = 0;int fd;const char *name;while ((c = getopt(argc, argv, “hm:r:v”)) != EOF) {switch (c) {case ‘m’:msglen = atoi(optarg);if (msglen < 0)goto usage;continue;case ‘r’:readcount = atoi(optarg);if (readcount < 0)goto usage;continue;case ‘v’:verbose++;continue;case ‘h’:case ‘?’:usage:fprintf(stderr,”usage: %s [-h] [-m N] [-r N] /dev/spidevB.D/n”,argv[0]);return 1;}}if ((optind + 1) != argc)goto usage;name = argv[optind];fd = open(name, O_RDWR);if (fd < 0) {perror(“open”);return 1;}dumpstat(name, fd);if (msglen)do_msg(fd, msglen);if (readcount)do_read(fd, readcount);close(fd);return 0;}备注：如果要设置模式，速率等，则可仿照以下语句：speed =10*1000*1000; //10MHzif (ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed) < 0) {perror(“SPI max_speed_hz”);return;}默认spi_io_transfer时，每个字节之间有延时。在atmel_spi_setup.c文件里去掉该延时语句：/* TODO: DLYBS and DLYBCT *///csr |= SPI_BF(DLYBS, 10);//csr |= SPI_BF(DLYBCT, 10);这样就可以达到无间隙快速传输批量数据。标准read(),write()两个函数仅适用于半双工传输，。在传输之间不激活片选。而SPI_IOC_MESSAGE(N)则是全双工传输，并且片选始终激活。SPI_IOC_MESSAGE传输长度有限制，默认是一页的长度，但是可以更改。spi_ioc_transfer结构的spi长度 是字节长度，16位传输的时候要注意。
懂得接受失败的人，就是懂得人生真谛的人，
