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C用法笔记

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pansyhou

U-boot​

8.19​

在uboot/common/board_f.c中，有这初始化波特率到gd的代码

  1. 弱函数声明接口

  2. 字符串获得config实现不同arch的初始化

    /**
     * Decode the integer value of an environment variable and return it.
     *
     * @param name      Name of environemnt variable
     * @param base      Number base to use (normally 10, or 16 for hex)
     * @param default_val   Default value to return if the variable is not
     *          found
     * @return the decoded value, or default_val if not found
     */
    ulong getenv_ulong(const char *name, int base, ulong default_val)
    {
        /*
         * We can use getenv() here, even before relocation, since the
         * environment variable value is an integer and thus short.
         */
        const char *str = getenv(name);

        return str ? simple_strtoul(str, NULL, base) : default_val;
    }

Linux​

THIS_MODULE​

#define THIS_MODULE ((struct module *)0)

static struct file_operations led_fops = {
    .owner = THIS_MODULE,
    .open = led_open,
    .read = led_read,
    .write = led_write,
    .release = led_release,
};

这是文件的fop结构体，重点在THIS_MODULE宏

这个字段说明谁是struct file_operations的所有者。这可以防止模块在运行时被卸载。当初始化为THIS_MODULE时，当前模块拥有其所有权。

可能和我想象中的不一样吧

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