Linux设备驱动探究第1天----spi驱动(1)
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Linux内核代码实在太大了,一个小小的模块也会让你手足无措,今天下午决心要把spi驱动好好看看。
首先分析spidev.c文件,这个文件中定义struct file_operations结构中的成员。成员有spidev_write、spidev_read和spidev_ioctl,前两者实现半双工通信,后者实现全双工通信。当然还有open和release等相关的成员,先忽略吧。
spidev_write -------->spidev_sync
spidev_write -------->spidev_sync
spidev_ioctl ------> spidev_message------->spidev_sync
详细文档见:点击打开链接
还有填充struct spi_drive数据结构体成员的函数,有spidev_probe,spidev_remove函数。以及设备驱动的初始化和退出函数:spidev_init和spidev_exit
代码分析见:点击打开链接
引用:
#include <linux/init.h> #include <linux/module.h> #include <linux/ioctl.h> #include <linux/fs.h> #include <linux/device.h> #include <linux/err.h> #include <linux/list.h> #include <linux/errno.h> #include <linux/mutex.h> #include <linux/slab.h> #include <linux/spi/spi.h> #include <linux/spi/spidev.h> #include <asm/uaccess.h> #define SPIDEV_MAJOR 153 //spidev主设备号 #define N_SPI_MINORS 32 /* ... up to 256 */ static DECLARE_BITMAP(minors, N_SPI_MINORS); //声明次设备位图 #define SPI_MODE_MASK (SPI_CPHA|SPI_CPOL|SPI_CS_HIGH|SPI_LSB_FIRST|SPI_3WIRE|SPI_LOOP|SPI_NO_CS|SPI_READY) struct spidev_data { dev_t devt; //设备号 spinlock_t spi_lock; //自旋锁 struct spi_device *spi; //spi设备结构体 struct list_head device_entry; struct mutex buf_lock; //互斥锁 unsigned users; //使用者计数 u8 *buffer; //缓冲区 }; static LIST_HEAD(device_list); //声明spi设备链表 static DEFINE_MUTEX(device_list_lock); //定义互斥锁 static unsigned bufsiz = 4096; //最大传输缓冲区大小 module_param(bufsiz, uint, S_IRUGO); MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message"); static void spidev_complete(void *arg) { complete(arg); //调用complete } static ssize_t spidev_sync(struct spidev_data *spidev, struct spi_message *message) { DECLARE_COMPLETION_ONSTACK(done); int status; message->complete = spidev_complete; //设置spi消息的complete方法 回调函数 message->context = &done; spin_lock_irq(&spidev->spi_lock); if (spidev->spi == NULL) //判断是否有指定对应的spi设备 status = -ESHUTDOWN; else status = spi_async(spidev->spi, message); //spi异步同步 spin_unlock_irq(&spidev->spi_lock); if (status == 0) { wait_for_completion(&done); //等待传输完成 status = message->status; //获取spi消息传输事务状态 if (status == 0) status = message->actual_length; //status等于传输的实际长度 } return status; //返回实际传输长度 } static inline ssize_t spidev_sync_write(struct spidev_data *spidev, size_t len) { struct spi_transfer t = { .tx_buf = spidev->buffer, //发送缓冲区 .len = len, //发送数据长度 }; struct spi_message m; spi_message_init(&m); //初始化spi消息(初始化spi传递事务队列) spi_message_add_tail(&t, &m); //添加spr传递到该队列 return spidev_sync(spidev, &m); //同步读写 } static inline ssize_t spidev_sync_read(struct spidev_data *spidev, size_t len) { struct spi_transfer t = { .rx_buf = spidev->buffer, //接收缓冲区 .len = len, //接收数据长度 }; struct spi_message m; spi_message_init(&m); //初始化spi消息(初始化spi传递事务队列) spi_message_add_tail(&t, &m); //添加spr传递到该队列 return spidev_sync(spidev, &m); //同步读写 } 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; if (count > bufsiz) //传输数据大于缓冲区容量 return -EMSGSIZE; spidev = filp->private_data; //从文件私有数据指针获取spidev_data mutex_lock(&spidev->buf_lock); //上互斥锁 status = spidev_sync_read(spidev, count); //同步读,返回传输数据长度 if (status > 0) { unsigned long missing; //丢失的数据个数 missing = copy_to_user(buf, spidev->buffer, status); //内核空间复制到用户空间 if (missing == status) //丢失的数据个数等于要传输的数据个数 status = -EFAULT; else status = status - missing; //传输成功的数据个数 } mutex_unlock(&spidev->buf_lock);//解互斥锁 return status; //返回读取成功的数据个数 } 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; if (count > bufsiz) //传输数据大于缓冲区容量 return -EMSGSIZE; spidev = filp->private_data; //从文件私有数据指针获取spidev_data mutex_lock(&spidev->buf_lock); //上互斥锁 missing = copy_from_user(spidev->buffer, buf, count); //用户空间复制到内核空间 if (missing == 0) { //传输失败个数为0 status = spidev_sync_write(spidev, count); //同步写,返回传输数据长度 } else status = -EFAULT; mutex_unlock(&spidev->buf_lock);//解互斥锁 return status; //返回写数据的实际个数 } static int spidev_message(struct spidev_data *spidev,struct spi_ioc_transfer *u_xfers, unsigned n_xfers) { struct spi_message msg; struct spi_transfer *k_xfers; struct spi_transfer *k_tmp; struct spi_ioc_transfer *u_tmp; unsigned n, total; u8 *buf; int status = -EFAULT; spi_message_init(&msg); //初始化spi消息(初始化spi传递事务队列) k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL); //分配spi传输指针内存 if (k_xfers == NULL) return -ENOMEM; buf = spidev->buffer; //获取spidev_data的缓冲区 total = 0; //n=xfers为spi_ioc_transfer个数,u_tmp = u_xfers为要处理的spi_ioc_transfer指针 for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers;n;n--, k_tmp++, u_tmp++) { k_tmp->len = u_tmp->len; //设置传输信息的长度 total += k_tmp->len; //累加传输信息的总长度 if (total > bufsiz) { //信息量超过bufsiz缓冲区最大容量 status = -EMSGSIZE; goto done; } if (u_tmp->rx_buf) { //接收缓冲区指针不为空 k_tmp->rx_buf = buf; //缓冲区指向buf if (!access_ok(VERIFY_WRITE, (u8 __user *)(uintptr_t) u_tmp->rx_buf,u_tmp->len)) goto done; } if (u_tmp->tx_buf) { //发送缓冲区指针不为空 k_tmp->tx_buf = buf; //缓冲区指针指向buf if (copy_from_user(buf, (const u8 __user *)(uintptr_t) u_tmp->tx_buf,u_tmp->len)) //用户空间复制数据到buf goto done; } buf += k_tmp->len; //缓冲区指针移动一个传输信息的长度 k_tmp->cs_change = !!u_tmp->cs_change; //设置cs_change k_tmp->bits_per_word = u_tmp->bits_per_word; //设置bits_per_word 一个字多少位 k_tmp->delay_usecs = u_tmp->delay_usecs; //设置delay_usecs 毫秒级延时 k_tmp->speed_hz = u_tmp->speed_hz; //设置speed_hz 速率 #ifdef VERBOSE dev_dbg(&spidev->spi->dev," xfer len %zd %s%s%s%dbits %u usec %uHz\n", u_tmp->len,u_tmp->rx_buf ? "rx " : "",u_tmp->tx_buf ? "tx " : "",u_tmp->cs_change ? "cs " : "", u_tmp->bits_per_word ? : spidev->spi->bits_per_word,u_tmp->delay_usecs,u_tmp->speed_hz ? : spidev->spi->max_speed_hz); #endif spi_message_add_tail(k_tmp, &msg); //添加spr传递到该队列 } //for循环的作用是将spi_ioc_transfer批量转换为spi传递结构体spi_transfer,然后添加进spi传递事务队列 status = spidev_sync(spidev, &msg); //同步读写 if (status < 0) goto done; buf = spidev->buffer; //获取spidev_data缓冲区指针 for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) { //批量从内核空间复制spi_ioc_transfer到用户空间 if (u_tmp->rx_buf) { //判断是否存在接收缓冲区 if (__copy_to_user((u8 __user *)(uintptr_t) u_tmp->rx_buf, buf,u_tmp->len)) { status = -EFAULT; goto done; } } buf += u_tmp->len; //buf指针位置调整指向下一个spi_ioc_transfer } status = total; //status等于实际传输的数据长度 done: kfree(k_xfers); //释放k_xfers return status; //返回实际传输的数据长度 } static long spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) { int err = 0; int retval = 0; struct spidev_data *spidev; struct spi_device *spi; u32 tmp; unsigned n_ioc; struct spi_ioc_transfer *ioc; if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC) //判断控制命令的类型 return -ENOTTY; if (_IOC_DIR(cmd) & _IOC_READ) //判断控制命令的方向是否为读read err = !access_ok(VERIFY_WRITE,(void __user *)arg, _IOC_SIZE(cmd)); //判断传输数据大小 if (err == 0 && _IOC_DIR(cmd) & _IOC_WRITE) //判断控制命令的方向是否为写write err = !access_ok(VERIFY_READ,(void __user *)arg, _IOC_SIZE(cmd)); //判断传输数据大小 if (err) return -EFAULT; spidev = filp->private_data; //从文件私有数据中获取spidev_data spin_lock_irq(&spidev->spi_lock); //上自旋锁 spi = spi_dev_get(spidev->spi); //获取spi设备 spin_unlock_irq(&spidev->spi_lock); //解自旋锁 if (spi == NULL) //获取spi设备失败 return -ESHUTDOWN; //则返回错误 mutex_lock(&spidev->buf_lock); //上互斥锁 switch (cmd) { case SPI_IOC_RD_MODE: //设置spi读模式 retval = __put_user(spi->mode & SPI_MODE_MASK,(__u8 __user *)arg); break; case SPI_IOC_RD_LSB_FIRST: //设置spi读最低有效位 retval = __put_user((spi->mode & SPI_LSB_FIRST) ? 1 : 0,(__u8 __user *)arg); break; case SPI_IOC_RD_BITS_PER_WORD: //设置spi读每个字含多个个位 retval = __put_user(spi->bits_per_word, (__u8 __user *)arg); break; case SPI_IOC_RD_MAX_SPEED_HZ: //设置spi读最大速率 retval = __put_user(spi->max_speed_hz, (__u32 __user *)arg); break; case SPI_IOC_WR_MODE: //设置spi写模式 retval = __get_user(tmp, (u8 __user *)arg); if (retval == 0) { u8 save = spi->mode; //获取spi设备模式 if (tmp & ~SPI_MODE_MASK) { retval = -EINVAL; break; } tmp |= spi->mode & ~SPI_MODE_MASK; spi->mode = (u8)tmp; retval = spi_setup(spi); //配置spi设备 if (retval < 0) spi->mode = save; else dev_dbg(&spi->dev, "spi mode %02x\n", tmp); } break; case SPI_IOC_WR_LSB_FIRST: //设置spi写最低有效位 retval = __get_user(tmp, (__u8 __user *)arg); if (retval == 0) { u8 save = spi->mode; //获取spi设备模式 if (tmp) spi->mode |= SPI_LSB_FIRST; else spi->mode &= ~SPI_LSB_FIRST; retval = spi_setup(spi); //配置spi设备 if (retval < 0) spi->mode = save; else dev_dbg(&spi->dev, "%csb first\n",tmp ? ‘l‘ : ‘m‘); } break; case SPI_IOC_WR_BITS_PER_WORD: //设置spi写每个字含多个个位 retval = __get_user(tmp, (__u8 __user *)arg); //用户空间获取数据 if (retval == 0) { u8 save = spi->bits_per_word; //获取spi设备 每个字含多少位 spi->bits_per_word = tmp; //更新新的spi设备 每个字含多少位 retval = spi_setup(spi); //配置spi设备 if (retval < 0) //配置失败 spi->bits_per_word = save; //还原spi设备 每个字含多少位 else dev_dbg(&spi->dev, "%d bits per word\n", tmp); } break; case SPI_IOC_WR_MAX_SPEED_HZ: //设置spi写最大速率 retval = __get_user(tmp, (__u32 __user *)arg); //用户空间获取数据 if (retval == 0) { u32 save = spi->max_speed_hz; //获取spi设备最大速率 spi->max_speed_hz = tmp; //更新新的spi设备最大速率 retval = spi_setup(spi); //配置spi设备 if (retval < 0) //配置失败 spi->max_speed_hz = save; //还原spi设备最大速率 else dev_dbg(&spi->dev, "%d Hz (max)\n", tmp); } break; default: //命令必须为写方向的命令,且传输数据必须是SPI_IOC_MESSAGE()修饰的命令 if (_IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0))|| _IOC_DIR(cmd) != _IOC_WRITE) { retval = -ENOTTY; break; } tmp = _IOC_SIZE(cmd); //计算传输数据大小 if ((tmp % sizeof(struct spi_ioc_transfer)) != 0) { //判断是否为spi_ioc_transfer对齐 retval = -EINVAL; break; } n_ioc = tmp / sizeof(struct spi_ioc_transfer); //计算出spi_ioc_transfer数据的个数 if (n_ioc == 0) break; ioc = kmalloc(tmp, GFP_KERNEL); //分配spi_ioc_transfer指针ioc内存 if (!ioc) { retval = -ENOMEM; break; } if (__copy_from_user(ioc, (void __user *)arg, tmp)) { //从用户空间复制到内核空间 kfree(ioc); //复制失败则释放ioc内存 retval = -EFAULT; break; } retval = spidev_message(spidev, ioc, n_ioc); //spidev消息处理 kfree(ioc); //释放ioc内存 break; } mutex_unlock(&spidev->buf_lock); //解互斥锁 spi_dev_put(spi); //增加spi设备的引用计数 return retval; } static int spidev_open(struct inode *inode, struct file *filp) { struct spidev_data *spidev; int status = -ENXIO; mutex_lock(&device_list_lock); //上互斥锁 list_for_each_entry(spidev, &device_list, device_entry) { //遍历device_list if (spidev->devt == inode->i_rdev) { //判断设备号找到对应的设备 status = 0; //设置状态为0 break; } } if (status == 0) { //找得到对应的设备 if (!spidev->buffer) { //spidev_data缓冲区为空 spidev->buffer = kmalloc(bufsiz, GFP_KERNEL); //则分配内存 if (!spidev->buffer) { //还空 dev_dbg(&spidev->spi->dev, "open/ENOMEM\n"); //调试了 status = -ENOMEM; } } if (status == 0) { //找得到对应的设备 spidev->users++; //spidev_data使用者计数++ filp->private_data = spidev; //spidev_data放在文件的私有数据里 nonseekable_open(inode, filp); //设置文件的打开模式(文件读写指针不会跟随读写操作移动) } } else pr_debug("spidev: nothing for minor %d\n", iminor(inode)); mutex_unlock(&device_list_lock); //接互斥锁 return status; } static int spidev_release(struct inode *inode, struct file *filp) { struct spidev_data *spidev; int status = 0; mutex_lock(&device_list_lock); spidev = filp->private_data; //获取spidev_data filp->private_data = NULL; //清除文件的私有数据指针 spidev->users--; //使用者个数-- if (!spidev->users) { //如果使用者个数为0 int dofree; kfree(spidev->buffer); //释放spidev_data的缓冲区内存 spidev->buffer = NULL; //清除spidev_data缓冲区指针 spin_lock_irq(&spidev->spi_lock); //上自旋锁 dofree = (spidev->spi == NULL); //判断spi设备是否与spidev_data解绑了 spin_unlock_irq(&spidev->spi_lock); //解自旋锁 if (dofree) //没有捆绑的spi设备 kfree(spidev); //则是否spidev_data内存 } mutex_unlock(&device_list_lock); return status; } static const struct file_operations spidev_fops = { //文件操作函数集 .owner = THIS_MODULE, .write = spidev_write, //写write .read = spidev_read, //读read .unlocked_ioctl = spidev_ioctl, //控制ioctl .open = spidev_open, //打开open .release = spidev_release, //释放release .llseek = no_llseek, //文件指针移动 no_llseek表示没有移动 }; static struct class *spidev_class; static int __devinit spidev_probe(struct spi_device *spi) { struct spidev_data *spidev; int status; unsigned long minor; spidev = kzalloc(sizeof(*spidev), GFP_KERNEL); //分配spidev_data内存 if (!spidev) return -ENOMEM; spidev->spi = spi; //设置spidev_data->spi(spi设备) spin_lock_init(&spidev->spi_lock); mutex_init(&spidev->buf_lock); INIT_LIST_HEAD(&spidev->device_entry); //初始化spidev_data入口链表 mutex_lock(&device_list_lock); minor = find_first_zero_bit(minors, N_SPI_MINORS); //查找次设备位图分配次设备号 if (minor < N_SPI_MINORS) { struct device *dev; spidev->devt = MKDEV(SPIDEV_MAJOR, minor); //计算出设备号 //创建设备/dev/spidev%d.%d(spidev总线号.片选号) dev = device_create(spidev_class, &spi->dev, spidev->devt,spidev, "spidev%d.%d",spi->master->bus_num, spi->chip_select); status = IS_ERR(dev) ? PTR_ERR(dev) : 0; } else { dev_dbg(&spi->dev, "no minor number available!\n"); status = -ENODEV; } if (status == 0) { //分配设备号成功 set_bit(minor, minors); //更新次设备位图 list_add(&spidev->device_entry, &device_list); //添加进设备链表 } mutex_unlock(&device_list_lock); if (status == 0) spi_set_drvdata(spi, spidev); //spi->dev->p->driver_data=spidev else kfree(spidev); return status; } static int __devexit spidev_remove(struct spi_device *spi) { struct spidev_data *spidev = spi_get_drvdata(spi); //根据spi设备获取spidev_data spin_lock_irq(&spidev->spi_lock); //上自旋锁 spidev->spi = NULL; //清空spidev_data->spi指针 spi_set_drvdata(spi, NULL); //spi->dev->p->driver_data=NULL spin_unlock_irq(&spidev->spi_lock); //解自旋锁 mutex_lock(&device_list_lock); //上互斥锁 list_del(&spidev->device_entry); //删除spidev_data入口链表 device_destroy(spidev_class, spidev->devt); //销毁/dev/spidev%d.%d clear_bit(MINOR(spidev->devt), minors); //清除次设备位图对应位 if (spidev->users == 0) //使用者个数为0 kfree(spidev); //释放spidev_data内存 mutex_unlock(&device_list_lock); //解互斥锁 return 0; } static struct spi_driver spidev_spi_driver = { //spi设备驱动 .driver = { .name = "spidev", .owner = THIS_MODULE, }, .probe = spidev_probe, //spidev的probe方法(当注册了modalias域为"spidev"的spi设备或板级设备,则会调用probe方法) .remove = __devexit_p(spidev_remove), //spidev的remove方法 }; static int __init spidev_init(void) //spidev接口初始化 { int status; BUILD_BUG_ON(N_SPI_MINORS > 256); //注册字符设备,主设备号SPIDEV_MAJOR=153,捆绑的设备操作函数集为spidev_fops status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops); if (status < 0) return status; spidev_class = class_create(THIS_MODULE, "spidev"); //创建设备类spidev_class 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设备驱动spidev_spi_driver if (status < 0) { class_destroy(spidev_class); unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name); } return status; } module_init(spidev_init); //声明初始化入口 static void __exit spidev_exit(void) //spidev接口销毁 { spi_unregister_driver(&spidev_spi_driver); //注销spi设备驱动spidev_spi_driver class_destroy(spidev_class); //注销设备类spidev_class unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name); //注销字符设备 } module_exit(spidev_exit); //声明初始化出口 MODULE_AUTHOR("Andrea Paterniani, <[email protected]>"); MODULE_DESCRIPTION("User mode SPI device interface"); MODULE_LICENSE("GPL"); MODULE_ALIAS("spi:spidev");
这里整理下ioctl的命令:
SPI_IOC_RD_MODE //读 模式 SPI_IOC_RD_LSB_FIRST //读 LSB SPI_IOC_RD_BITS_PER_WORD //读 每字多少位 SPI_IOC_RD_MAX_SPEED_HZ //读 最大速率 SPI_IOC_WR_MODE //写 模式 SPI_IOC_WR_LSB_FIRST //写 LSB SPI_IOC_WR_BITS_PER_WORD //写 每字多少位 SPI_IOC_WR_MAX_SPEED_HZ //写 最大速率 SPI_IOC_MESSAGE(n) //传输n个数据包
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