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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
1.4t什么意思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-$(CONFIG_VIDEO_S3C_CAMIF) += s3c-camif/
5、继续查看s3c-camif⽬录的代码结构
李山# Makefile for s3c244x/s3c64xx CAMIF driver
s3c-camif-objs := camif-core.o camif-capture.o camif-regs.o
obj-$(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,
王者荣耀赵云出装.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,
安家电视剧结局.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,
黄鹤楼漫天游多少钱.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,
};
独生子补贴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。
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