Android udev /dev 設備節點權限

/*************************************************************************
 *                  Android udev /dev 設備節點權限
 * 說明：
 *     現在的Linux系統設備節點權限一般都是通過動態配置，之前一直沒找到具體
 * 在哪里配置的說明，這次在看參考書的時候發現ueventd.rc就是用來做這件事的。
 *
 *                                   2016-5-14 深圳 南山平山村 曾劍鋒
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一、參考文檔：
    Embedded Android
        https://www.google.co.id/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&ved=0ahUKEwiWwcrbqtjMAhWDppQKHdhjBroQFgg5MAQ&url=http%3A%2F%2Fwww.staroceans.org%2Fkernel-and-driver%2F%255BEmbedded.Android(2013.3)%255D.Karim.Yaghmour.pdf&usg=AFQjCNHe5Ey14egLQXgmOpP-PGN510ALgA

二、原文：
    1.　頁碼：58
    2. 內容：
    udev events
    As I explained earlier, access to devices in Linux is done through nodes within the /dev directory. In the old days, Linux distributions would ship with thousands of entries in that directory to accommodate all possible device configurations. Eventually, though, a few schemes were proposed to make the creation of such nodes dynamic. For some time now, the system in use has been udev, which relies on runtime events generated by the kernel every time hardware is added or removed from the system.  In most Linux distributions, the handling of udev hotplug events is done by the udevd daemon. In Android, these events are handled by the ueventd daemon built as part of Android’s init and accessed through a symbolic link from /sbin/ueventd to /init. To know which entries to create in /dev, ueventd relies on the /ueventd.rc and /ueventd.<device_name>.rc files.

三、總結：
    之前遇到需要修改權限之類的事情，一般都是在init.rc中進行修改，那時候覺得挺奇怪的，因為一般會有專門給設備節點設置權限的文件，那里明顯不是，但也沒找到准確的地方，現在終於找到依據了。