对于现代嵌入式设备,特别是手机来说,摄像头是很重要的一个设备。很多同学买手机,一看颜值,第二就看摄像头拍照如何。所以,从某个角度来说,摄像头是各个厂家主打的应用功能。那么,linux是如何支持摄像头的,我们可以来看一下?
1、代码目录地址
drivers/media
2、v4l2框架
目前linux上的camera都是按照v4l2框架来设计,它的地址位于drivers/media/v4l2-core
3、查看三星soc是如何支持camera的,可以查看drviers/media/platform/Kconfig
config VIDEO_S3C_CAMIF
tristate "Samsung S3C24XX/S3C64XX SoC Camera Interface driver"
depends on VIDEO_V4L2 && I2C && VIDEO_V4L2_SUBDEV_API
depends on PM
depends on ARCH_S3C64XX || PLAT_S3C24XX || COMPILE_TEST
depends on HAS_DMA
select VIDEOBUF2_DMA_CONTIG
---help---
This is a v4l2 driver for s3c24xx and s3c64xx SoC series camera
host interface (CAMIF).
To compile this driver as a module, choose M here: the module
will be called s3c-camif.
4、从Kconfig确认除了VIDEO_V4L2和VIDEO_V4L2_SUBDEV_API之外,它只依赖自己的目录
obj-$(CONFIG_VIDEO_S3C_CAMIF) += s3c-camif/
5、继续查看s3c-camif目录的代码结构
# Makefile for s3c244x/s3c64xx CAMIF driver
s3c-camif-objs := camif-core.o camif-capture.o camif-regs.o
obj-$(CONFIG_VIDEO_S3C_CAMIF) += s3c-camif.o
6、Makefile说的很清楚,它主要依赖camif-*.c三个文件
通过阅读,确认camif-core.c是注册文件
camif-regs.c是寄存器读写文件
camif-capture.c是主要的操作文件、接口文件
7、确认v4l2的函数操作接口
static const struct v4l2_ioctl_ops s3c_camif_ioctl_ops = {
.vidioc_querycap = s3c_camif_vidioc_querycap,
.vidioc_enum_input = s3c_camif_vidioc_enum_input,
.vidioc_g_input = s3c_camif_vidioc_g_input,
.vidioc_s_input = s3c_camif_vidioc_s_input,
.vidioc_enum_fmt_vid_cap = s3c_camif_vidioc_enum_fmt,
.vidioc_try_fmt_vid_cap = s3c_camif_vidioc_try_fmt,
.vidioc_s_fmt_vid_cap = s3c_camif_vidioc_s_fmt,
.vidioc_g_fmt_vid_cap = s3c_camif_vidioc_g_fmt,
.vidioc_g_selection = s3c_camif_g_selection,
.vidioc_s_selection = s3c_camif_s_selection,
.vidioc_reqbufs = s3c_camif_reqbufs,
.vidioc_querybuf = s3c_camif_querybuf,
.vidioc_prepare_buf = s3c_camif_prepare_buf,
.vidioc_create_bufs = s3c_camif_create_bufs,
.vidioc_qbuf = s3c_camif_qbuf,
.vidioc_dqbuf = s3c_camif_dqbuf,
.vidioc_streamon = s3c_camif_streamon,
.vidioc_streamoff = s3c_camif_streamoff,
.vidioc_subscribe_event = v4l2_ctrl_subscribe_event,
.vidioc_unsubscribe_event = v4l2_event_unsubscribe,
.vidioc_log_status = v4l2_ctrl_log_status,
};
and
static const struct v4l2_file_operations s3c_camif_fops = {
.owner = THIS_MODULE,
.open = s3c_camif_open,
.release = s3c_camif_close,
.poll = s3c_camif_poll,
.unlocked_ioctl = video_ioctl2,
.mmap = s3c_camif_mmap,
};
static const struct vb2_ops s3c_camif_qops = {
.queue_setup = queue_setup,
.buf_prepare = buffer_prepare,
.buf_queue = buffer_queue,
.wait_prepare = vb2_ops_wait_prepare,
.wait_finish = vb2_ops_wait_finish,
.start_streaming = start_streaming,
.stop_streaming = stop_streaming,
};
const struct vb2_mem_ops vb2_dma_contig_memops = {
.alloc = vb2_dc_alloc,
.put = vb2_dc_put,
.get_dmabuf = vb2_dc_get_dmabuf,
.cookie = vb2_dc_cookie,
.vaddr = vb2_dc_vaddr,
.mmap = vb2_dc_mmap,
.get_userptr = vb2_dc_get_userptr,
.put_userptr = vb2_dc_put_userptr,
.prepare = vb2_dc_prepare,
.finish = vb2_dc_finish,
.map_dmabuf = vb2_dc_map_dmabuf,
.unmap_dmabuf = vb2_dc_unmap_dmabuf,
.attach_dmabuf = vb2_dc_attach_dmabuf,
.detach_dmabuf = vb2_dc_detach_dmabuf,
.num_users = vb2_dc_num_users,
};
8、和sd一样,接口比较简单,但是要深入了解camera,v4l2是绕不过去的。
这一点和sd卡、usb、asoc是一样的。
标签:camif,dc,vb2,vidioc,摄像头,linux,驱动,v4l2,s3c From: https://blog.51cto.com/feixiaoxing/5881995