问题
I need to access an USB camera connected to my (rooted) Android. I'm on a Samsung Galaxy S4 with Android 4.2.2. I want to access it with a normal app, so I need the device to be world readable.
I can connect via shell and type
root@android:/ # su
root@android:/ # cd /dev
root@android:/dev # chmod 666 video4
and it works. But each time I disconnect the camera, and reconnect it, I have to do it again.
Via shell I can remount the root file system r/w
mount -o rw,remount -t rootfs rootfs /
and then edit the file /ueventd.rc (actually it's /ueventd.qcom.rc )
and add
/dev/video* 0666 system camera
But even if I put 666 I only get
root@android:/dev # ls -la video4
crw-rw---- system camera 81, 18 2013-08-08 10:14 video4
Is there a way to grant a 666 permission permanently? So that each time I connect the camera it gets the right file permissions?
Thanks
回答1:
After you replace the /ueventd.qcom.rc file, you must restart /sbin/ueventd service. Actually, it will restart automatically, you only need to find it ps u, and kill the pid.
Note that Samsung restores rootfs on every reboot. The way I handle it, I keep the changed copy of ueventd.qcom.rc in /data/local/tmp, and issue
su -c mount -o remount,rw /
su -c cp /data/local/tmp/ueventd.qcom.rc /
ps ueventd
>
USER PID PPID VSIZE RSS WCHAN PC NAME
root 198 1 1136 448 ffffffff 00000000 S /sbin/ueventd
kill198
回答2:
There are Triggers available in init.rc, device-add- and device-removed, it seems perhaps this could give you the opportunity to set the permissions: https://github.com/android/platform_system_core/blob/master/init/readme.txt#L126
来源：https://stackoverflow.com/questions/18121626/android-how-to-grant-666-privs-to-a-device-via-ueventd-rc