增加字符设备参考(未完成).

Signed-off-by: ithink.chan <chenyang@autoai.com>

Linux/KernelDriver/Char/Makefile

@@ -0,0 +1,14 @@
+obj-m:= \
+    demochar.o
+
+demochar-objs:= \
+	demo_char.o
+
+EXTRA_CFLAGS += \
+    -I$(PWD)
+
+all:
+	$(MAKE) -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
+
+clean:
+	$(MAKE) -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

Linux/KernelDriver/Char/demo_char.c

@@ -0,0 +1,134 @@
+/**
+ * @file    demo_char.c
+ * @author  Rick Chan (cy187lion@sina.com)
+ * @brief   Linux char driver demo.
+ * @version 0.1.0
+ * @date    2020-04-27
+ * 
+ * @copyright Copyright (c) 2020
+ * 
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/miscdevice.h>
+#include <linux/uaccess.h>
+
+MODULE_AUTHOR("Rick Chan");
+MODULE_LICENSE("GPL");
+
+#define DEMO_MAGIC     'R'
+#define DEMO_IOC_SIZE   8
+#define DEMO_CTL_IOC   _IOC(_IOC_READ|_IOC_WRITE, DEMO_MAGIC, 0, DEMO_IOC_SIZE)
+#define DEMO_CTL_IO    _IO(DEMO_MAGIC, 1)
+#define DEMO_CTL_IOR   _IOR(DEMO_MAGIC, 2, uint16_t)
+#define DEMO_CTL_IOW   _IOW(DEMO_MAGIC, 3, int32_t)
+#define DEMO_CTL_IOWR  _IOWR(DEMO_MAGIC, 4, uint32_t)
+#define DEMO_CTL_MAX    5
+
+static int demo_open(struct inode *inode, struct file* filp)
+{
+    return 0;
+}
+
+static int demo_release(struct inode *inode, struct file* filp)
+{
+    return 0;
+}
+
+static loff_t demo_llseek(struct file *filp, loff_t offset, int origin)
+{
+    return filp->f_pos;
+}
+
+static ssize_t demo_read(struct file *filp, char __user *buffer, size_t count, loff_t *offset)
+{
+    const char __user *p = buffer;
+    return p-buffer;
+}
+
+static ssize_t demo_write(struct file *filp, const char __user *buffer, size_t count, loff_t *offset)
+{
+    const char __user *p = buffer;
+    return p-buffer;
+}
+
+static long demo_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+    // 检测 cmd 合法性
+    if (DEMO_MAGIC!=_IOC_TYPE(cmd)) 
+        return -EINVAL;
+    if (DEMO_CTL_MAX<_IOC_NR(cmd)) 
+        return -EINVAL;
+
+    switch(cmd)
+    {
+    case DEMO_CTL_IOC:
+       {
+        uint8_t tmp[DEMO_IOC_SIZE];
+        copy_from_user(&tmp, (void*)arg, _IOC_SIZE(cmd));
+        copy_to_user((void*)arg, &tmp, _IOC_SIZE(cmd));
+    }
+        break;
+    case DEMO_CTL_IO:
+        break;
+    case DEMO_CTL_IOR:
+    {
+        uint16_t tmp = 0x55AA;
+        copy_to_user((void*)arg, &tmp, _IOC_SIZE(cmd));
+    }
+        break;
+    case DEMO_CTL_IOW:
+    {
+        int32_t tmp = 0;
+        copy_from_user(&tmp, (void*)arg, _IOC_SIZE(cmd));
+    }
+        break;
+    case DEMO_CTL_IOWR:
+    {
+        uint32_t tmp = 0;
+        copy_from_user(&tmp, (void*)arg, _IOC_SIZE(cmd));
+        copy_to_user((void*)arg, &tmp, _IOC_SIZE(cmd));
+    }
+        break;
+    default:
+        return -ENOIOCTLCMD;
+    }
+    return 0;
+}
+
+static int demo_mmap(struct file* filp, struct vm_area_struct* vma)
+{
+    return 0;
+}
+
+static struct file_operations demo_fops = {
+    .owner          = THIS_MODULE,
+    .open           = demo_open,
+    .release        = demo_release,
+    .llseek         = demo_llseek,
+    .read           = demo_read,
+    .write          = demo_write,
+    .unlocked_ioctl = demo_ioctl,
+    .mmap           = demo_mmap
+};
+
+static struct miscdevice demo_dev = {
+    .minor  = MISC_DYNAMIC_MINOR,   // Dynamically allocate minor.
+    .name   = "demo_char",
+    .fops   = &demo_fops,
+};
+
+static int __init demo_init(void)
+{
+    misc_register(&demo_dev);
+    return 0;
+}
+
+static void __exit demo_exit(void)
+{
+    misc_deregister(&demo_dev);
+}
+
+module_init(demo_init);
+module_exit(demo_exit);