Android P Auto版本evs_app解析之二：evs_app启动和运行

最近在调试Android Auto版本的evs_app程序。

evs_app相关参考：
《Android P Auto版本evs_app解析之一：evs_app代码架构和通信机制》
《Android P Auto版本evs_app解析之二：evs_app启动和运行》

一、检查摄像头设备

驱动层生成的摄像头设备节点在dev下面查看。adb进入系统目录dev下，ls -l查看摄像头；
生成的摄像头为：dev/video0，dev/video1，dev/video2，dev/video3；
我做实验这里有四个摄像头。

二、运行evs_app程序报错

evs_app是可执行的二进制文件，在system/bin目录下。
adb shell进入系统目录，执行start evs_app启动evs_app.

1、驱动层代码报错

看下面的打印，没有权限对video*设备进行访问。所以没有找到有效的摄像头设备

2019-06-13 18:14:16.420 1909-1963/? I/EvsDriver: Starting dev/video* enumeration
2019-06-13 18:14:16.428 1909-1909/? W/VideoFile-Poll-: type=1400 audit(0.0:2044): avc: denied { read write } for name="video3" dev="tmpfs" ino=9980 scontext=u:r:hal_evs_driver:s0 tcontext=u:object_r:ad_camera_device:s0 tclass=chr_file permissive=0
2019-06-13 18:14:16.428 1909-1909/? W/VideoFile-Poll-: type=1400 audit(0.0:2045): avc: denied { read write } for name="video2" dev="tmpfs" ino=9979 scontext=u:r:hal_evs_driver:s0 tcontext=u:object_r:ad_camera_device:s0 tclass=chr_file permissive=0
2019-06-13 18:14:16.428 1909-1909/? W/VideoFile-Poll-: type=1400 audit(0.0:2046): avc: denied { read write } for name="video1" dev="tmpfs" ino=9978 scontext=u:r:hal_evs_driver:s0 tcontext=u:object_r:ad_camera_device:s0 tclass=chr_file permissive=0
2019-06-13 18:14:16.428 1909-1909/? W/VideoFile-Poll-: type=1400 audit(0.0:2047): avc: denied { read write } for name="video0" dev="tmpfs" ino=20016 scontext=u:r:hal_evs_driver:s0 tcontext=u:object_r:ad_camera_device:s0 tclass=chr_file permissive=0
2019-06-13 18:14:16.431 1909-1963/? I/EvsDriver: enum name:mxc_isi.0.m2m
     path:/dev/video4
2019-06-13 18:14:16.434 1909-1963/? I/EvsDriver: Found 1 qualified video capture devices of 7 checked

2、evs_app应用层也报错提示没有找到摄像头

2019-06-13 18:53:38.331 1909-1909/? D/EvsDriver: openCamera
2019-06-13 18:53:38.331 1909-1909/? E/EvsDriver: Requested camera mxc_isi.0.capture not found
2019-06-13 18:53:38.332 3272-3274/? E/EvsApp: Failed to allocate new EVS Camera interface for mxc_isi.0.capture
2019-06-13 18:53:38.332 3272-3274/? E/EvsApp: Failed to set up video texture for mxc_isi.0.capture (reverse,park)
2019-06-13 18:53:38.332 3272-3274/? E/EvsApp: New renderer failed to activate
2019-06-13 18:53:38.332 3272-3274/? E/EvsApp: selectStateForCurrentConditions failed so we're going to die
2019-06-13 18:53:38.332 3272-3274/? W/EvsApp: EvsSt