1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159
| #include <linux/module.h> #include <linux/init.h> #include <linux/fs.h> #include <asm/uaccess.h> #include <linux/wait.h> #include <linux/semaphore.h> #include <linux/sched.h> #include <linux/cdev.h> #include <linux/types.h> #include <linux/kdev_t.h> #include <linux/device.h> #define MAXNUM 100 #define MAJOR_NUM 456 struct Scull_Dev { struct cdev devm; struct semaphore sem; wait_queue_head_t outq; int flag; char buffer[MAXNUM + 1]; char *rd, *wr, *end; }; struct Scull_Dev globalvar;
int major = MAJOR_NUM; static ssize_t globalvar_read(struct file *, char *, size_t, loff_t *); static ssize_t globalvar_write(struct file *, const char *, size_t, loff_t *); static int globalvar_open(struct inode *inode, struct file *filp); static int globalvar_release(struct inode *inode, struct file *filp); struct file_operations globalvar_fops = { .read = globalvar_read, .write = globalvar_write, .open = globalvar_open, .release = globalvar_release, }; static int globalvar_init(void) { int result = 0; int err = 0; dev_t dev = MKDEV(major, 0); if (major) { result = register_chrdev_region(dev, 1, "charmem"); } else { result = alloc_chrdev_region(&dev, 0, 1, "charmem"); major = MAJOR(dev); } if (result < 0) return result; cdev_init(&globalvar.devm, &globalvar_fops); globalvar.devm.owner = THIS_MODULE; err = cdev_add(&globalvar.devm, dev, 1); if (err) printk(KERN_INFO "Error %d adding char_mem device", err); else { printk("globalvar register success\n"); sema_init(&globalvar.sem, 1); init_waitqueue_head(&globalvar.outq); globalvar.rd = globalvar.buffer; globalvar.wr = globalvar.buffer; globalvar.end = globalvar.buffer + MAXNUM; globalvar.flag = 0; } return 0; } static int globalvar_open(struct inode *inode, struct file *filp) { try_module_get(THIS_MODULE); printk("This chrdev is in open\n"); return (0); } static int globalvar_release(struct inode *inode, struct file *filp) { module_put(THIS_MODULE); printk("This chrdev is in release\n"); return (0); } static void globalvar_exit(void) { cdev_del(&globalvar.devm); unregister_chrdev_region(MKDEV(major, 0), 1); } static ssize_t globalvar_read(struct file *filp, char *buf, size_t len, loff_t *off) { if (wait_event_interruptible(globalvar.outq, globalvar.flag != 0)) { return -ERESTARTSYS; } if (down_interruptible(&globalvar.sem)) { return -ERESTARTSYS; } globalvar.flag = 0; printk("into the read function\n"); printk("the rd is %c\n", *globalvar.rd); if (globalvar.rd < globalvar.wr) len = min(len, (size_t)(globalvar.wr - globalvar.rd)); else len = min(len, (size_t)(globalvar.end - globalvar.rd)); printk("the len is %d\n", len); if (raw_copy_to_user(buf, globalvar.rd, len)) { printk(KERN_ALERT "copy failed\n"); up(&globalvar.sem); return -EFAULT; } printk("the read buffer is %s\n", globalvar.buffer); globalvar.rd = globalvar.rd + len; if (globalvar.rd == globalvar.end) globalvar.rd = globalvar.buffer; up(&globalvar.sem); return len; } static ssize_t globalvar_write(struct file *filp, const char *buf, size_t len, loff_t *off) { if (down_interruptible(&globalvar.sem)) { return -ERESTARTSYS; } if (globalvar.rd <= globalvar.wr) len = min(len, (size_t)(globalvar.end - globalvar.wr)); else len = min(len, (size_t)(globalvar.rd - globalvar.wr - 1)); printk("the write len is %d\n", len); if (raw_copy_from_user(globalvar.wr, buf, len)) { up(&globalvar.sem); return -EFAULT; } printk("the write buffer is %s\n", globalvar.buffer); printk("the len of buffer is %d\n", strlen(globalvar.buffer)); globalvar.wr = globalvar.wr + len; if (globalvar.wr == globalvar.end) globalvar.wr = globalvar.buffer; up(&globalvar.sem); globalvar.flag = 1; wake_up_interruptible(&globalvar.outq); return len; } module_init(globalvar_init); module_exit(globalvar_exit); MODULE_LICENSE("GPL");
|