编写Linux下的设备驱动程序课件

1、编写Linux下的设备驱动程序What we have learned?用module实现设备驱动程序init_module, cleanup_module设备也是文件；设备由主设备号、次设备号唯一标识mknod /dev/status c 0登记/注销设备register_chrdev, unregister_chrdevstruct file_operations (include/linux/fs.h)实现file_operations结构中指定的操作What we have learned? (contd)拷贝数据to/from用户空间copy_to_user, copy_from_u

2、ser使用计数(usage count)每个module保留一个usage count宏：MOD_INC_USE_COUNT, MOD_DEC_USE_COUNT, MOD_IN_USE:int register_chrdev(unsigned int major, const char *name, struct file_operations *fops);int unregister_chrdev(unsigned int major, const char *name);:unsigned long copy_to_user(void *to, const void *from, un

3、signed long count);unsigned long copy_from_user(void *to, const void *from, unsigned long count);:struct file_operations int (*open) (struct inode *, struct file *);int (*flush) (struct file *);int (*release) (struct inode *, struct file *);loff_t (*llseek) (struct file *, loff_t, int);ssize_t (*rea

4、d) (struct file *, char *, size_t, loff_t *);ssize_t (*write) (struct file *, const char *, size_t, loff_t *); ;:struct file的几个关键字段mode_t f_mode;loff_t f_pos;unsigned int f_flags;struct file_operations *f_op;void *private_data;struct dentry *f_dentry;What are we still to learn?TimingHardware managem

5、entI/O ports & I/O memoryInterrupt handlingProgramming I/OTwo types of instructions can support I/O:special-purpose I/O instructions;memory-mapped load/store instructions.Intel x86 provides in, out instructions. Most other CPUs use memory-mapped I/O.I/O instructions do not preclude memory-mapped I/O

6、.Using I/O ports:int check_region(unsigned long start, unsigned long len);struct resource *request_region(unsigned long start, unsigned long len, char *name);void release_region(unsigned long start, unsigned long len);Using I/O ports (contd):Read/write 8-bit ports (byte width):unsigned intb(unsigned

7、 port);unsigned outb(unsigned char byte, unsigned port);Read/write 16-bit ports (word width):unsigned intw(unsigned port);unsigned outw(unsigned short word, unsigned port);Read/write 32-bit ports:unsigned intl(unsigned port);unsigned outl(unsigned longword, unsigned port);Interrupt handlingInstallin

8、g an interrupt handlerImplementing a handlerInstalling an Interrupt Handlerrequest_irq, free_irqint request_irq(unsigned int irq, void (*handler)(int, void *, struct pt_regs *), unsigned long flags, const char *dev_name, void *dev_id);void free_irq(unsigned int irq, void *dev_id);调用时机Implementing a

9、handlerstatic void sample_interrupt(int irq, void *dev_id, struct pt_regs *regs);irq: interrupt numberdev_id: client data (private data used by the driver)regs: (rarely used) a snapshot of the processors context before the processor entered interrupt codeImplementing a handler (contd)等待队列(wait queue

10、)wait_queue_head_t类型init_waitqueue_headinterruptible_sleep_on wake_up_interruptibleCode examplesvoid short_interrupt(int irq, void *dev_id, struct pt_regs *regs) struct timeval tv; int written; do_gettimeofday(&tv); /* Write a 16-byte record. Assume PAGE_SIZE is a multiple of 16 */ written = sprintf

11、(char *)short_head,%08u.%06un, (int)(tv.tv_sec % 100000000), (int)(tv.tv_usec); short_incr_bp(&short_head, written); wake_up_interruptible(&short_queue);Code examples (contd)ssize_t short_i_read (struct file *filp, char *buf, size_t count, loff_t *f_pos) int count0; while (short_head = short_tail) i

12、nterruptible_sleep_on(&short_queue); if (signal_pending (current) /* a signal arrived */ return -ERESTARTSYS; /* tell the fs layer to handle it */ count0 = short_head - short_tail; if (count0 0) /* wrapped */ count0 = short_buffer + PAGE_SIZE - short_tail; if (count0 count) count = count0; if (copy_to_user(buf, (char *)short_tail, count) return -EFAULT; short_incr_bp (&short_tail, count); return count;Bottom-Half (BH) Processing中断处理程序尽量短小top half: 实际响应中断的例程bottom half: 被top half 调度，并在稍后更安全的时候运行的例程将