在imx6ull中加入ov5640模块

本来觉得是一件很简单的事情但是走了很多的弯路，记录一下调试过程。

1. 先使用正点原子提供的出厂内核把摄像头影像调试出来，然后cat /dev/video1，看一下video1牵扯到哪些模块，可以看到需要ov5640_camera.ko和 mx6s_capture.ko这两个模块。

root@ATK-IMX6U:/mnt/mxc/subdev# cat /dev/video1
[ 234.765777] ------------[ cut here ]------------
[ 234.770851] WARNING: CPU: 0 PID: 1362 at drivers/media/v4l2-core/videobuf2-core.c:2822 __vb2_init_fileio+0x124/0x31c()
[ 234.783858] Modules linked in: ov5640_camera mx6s_capture icm20608(O)
[ 234.791720] CPU: 0 PID: 1362 Comm: cat Tainted: G W O 4.1.15 #1
[ 234.798753] Hardware name: Freescale i.MX6 Ultralite (Device Tree)
[ 234.805019] [<80015dbc>] (unwind_backtrace) from [<80012748>] (show_stack+0x10/0x14)
[ 234.812783] [<80012748>] (show_stack) from [<8081e1ec>] (dump_stack+0x84/0xc4)
[ 234.820061] [<8081e1ec>] (dump_stack) from [<80036bc0>] (warn_slowpath_common+0x80/0xb0)
[ 234.828196] [<80036bc0>] (warn_slowpath_common) from [<80036c8c>] (warn_slowpath_null+0x1c/0x24)
[ 234.837019] [<80036c8c>] (warn_slowpath_null) from [<80549ac8>] (__vb2_init_fileio+0x124/0x31c)
[ 234.845760] [<80549ac8>] (__vb2_init_fileio) from [<8054a51c>] (__vb2_perform_fileio+0x498/0x5e4)
[ 234.854685] [<8054a51c>] (__vb2_perform_fileio) from [<8054a680>] (vb2_read+0x18/0x20)
[ 234.862625] [<8054a680>] (vb2_read) from [<7f004c70>] (mx6s_csi_read+0x4c/0x64 [mx6s_capture])
[ 234.871303] [<7f004c70>] (mx6s_csi_read [mx6s_capture]) from [<80532818>] (v4l2_read+0x60/0x98)
[ 234.880046] [<80532818>] (v4l2_read) from [<800e9c90>] (__vfs_read+0x20/0xd4)
[ 234.887220] [<800e9c90>] (__vfs_read) from [<800ea428>] (vfs_read+0x7c/0x104)
[ 234.894392] [<800ea428>] (vfs_read) from [<800eacc8>] (SyS_read+0x44/0x9c)
[ 234.901280] [<800eacc8>] (SyS_read) from [<8000f480>] (ret_fast_syscall+0x0/0x3c)
[ 234.915272] —[ end trace ed21faed4da06c6d ]—

以下调试都是在nxp原厂内核基础上进行的, 这是为了学习

2. 查看ov5640_camera.ko和 mx6s_capture.ko相关的Makefile和config配置，可见内核需要配置VIDEO_MXC_CSI_CAMERA和MXC_CAMERA_OV5640两个配置项。

Makefile:
obj-$(CONFIG_VIDEO_MXC_CSI_CAMERA) += mx6s_capture.o

ov5640_camera-objs := ov5640.o
obj-$(CONFIG_MXC_CAMERA_OV5640) += ov5640_camera.o

Kconfig:
config VIDEO_MXC_CSI_CAMERA
tristate “CSI camera support”
depends on VIDEO_MXC_CAPTURE && VIDEO_V4L2
—help—
This is the video4linux2 capture driver based on CSI module.

config MXC_CAMERA_OV5640
tristate “OmniVision ov5640 camera support”
depends on VIDEO_MXC_CAPTURE && I2C
—help—
If you plan to use the ov5640 Camera with your MXC system, say Y here.

3. 当然，仅仅配置那两项肯定是不行的，经过了几次尝试后后发现能让影像输出的配置如下。
   
   
   

4. NXP原厂提供ov5640.c文件也需要替换成正点原子出厂的ov5640.c。不然影像花屏，无法辨认物体。替换后影像清楚很多可以辨认物体了。

5. 重新使用正点原子手册《I.MX6U嵌入式Linux C应用编程指南V1.4.pdf》第三十四章 实战小项目之视频监控，把影响调试了出来。