Linux多媒体子系统01：从用户空间使用V4L2子系统笔记配套示例代码

#include <unistd.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <stdio.h> #include <sys/ioctl.h> #include <stdlib.h> #include <linux/types.h> #include <linux/videodev2.h> #include <malloc.h> #include <math.h> #include <string.h> #include <sys/mman.h> #include <errno.h> #include <assert.h> #include <poll.h> #include "ion.h" #include "dma-buf.h" #define CLEAR(x) memset(&(x), 0, sizeof(x)) #define BUF_COUNT 3 // 当前实验环境中，图像格式最多3个plane #define MAX_PLANE 3 struct user_plane { // 缓冲区内存起始虚拟地址 void *start; // 缓冲区内存长度 int len; // 缓冲区内存起始物理地址 unsigned long paddr; // 根据缓冲区内存类型维护的元数据 union { // mmap类型 unsigned int offset; // userptr类型 unsigned long userptr; // dmabuf类型 int fd; } m; }; struct user_buf { // 缓冲区内存的plane个数 int planes_num; // 缓冲区内存每个plane的信息 struct user_plane planes[MAX_PLANE]; }; struct user_buf user_bufs[BUF_COUNT]; static int alloc_ion_buffer(int fd, int len, int *dmabuf_fd, unsigned long *paddr, unsigned long *vaddr) { struct ion_allocation_data alloc_data; unsigned int heap_id = 4; int ret = 0; if (!dmabuf_fd || !paddr || !vaddr) { printf("invalid argument\n"); goto err; } CLEAR(alloc_data); alloc_data.len = len; alloc_data.heap_id_mask = heap_id; alloc_data.flags = ION_HEAP_TYPE_DMA; ret = ioctl(fd, ION_IOC_ALLOC, &alloc_data); if (ret < 0) { perror("ION_IOC_ALLOC error"); goto err; } *dmabuf_fd = alloc_data.fd; printf("============ after ION_IOC_ALLOC ============\n"); printf("alloc_data.len = 0x%llx\n", alloc_data.len); printf("alloc_data.heap_id_mask = 0x%x\n", alloc_data.heap_id_mask); printf("alloc_data.flags = %d\n", alloc_data.flags); printf("alloc_data.fd = %d\n", alloc_data.fd); printf("=============================================\n\n"); // 获取分配内存的物理地址 struct dma_buf_phys dma_phys; CLEAR(dma_phys); ret = ioctl(alloc_data.fd, DMA_BUF_IOCTL_PHYS, &dma_phys); if (ret < 0) { perror("DMA_BUF_IOCTL_PHYS error"); goto err; } *paddr = dma_phys.phys; printf("============ after DMA_BUF_IOCTL_PHYS ============\n"); printf("sizeof(struct dma_buf_phys) = %ld\n", sizeof(struct dma_buf_phys)); printf("dma_phys.phys = 0x%lx\n", dma_phys.phys); printf("==================================================\n\n"); // 将分配的内存映射到进程用户空间 char *virt_addr = NULL; virt_addr = (char *)mmap(0, len, PROT_READ | PROT_WRITE, MAP_SHARED, alloc_data.fd, 0); if (vaddr == MAP_FAILED) { perror("mmap error\n"); goto err; } *vaddr = (unsigned long)virt_addr; printf("============ after mmap ============\n"); printf("virt_addr = %p\n", virt_addr); printf("====================================\n\n"); return 0; err: return -1; } /* * buffer_export: 导出single-planar格式的mmap类型缓冲区内存 * v4lfd: V4L2设备文件描述符 * bt: 缓冲区类型 * index: 要导出的缓冲区序号 * dmafd[OUT]: 返回导出的dmabuf文件描述符 * 返回值: 成功返回0，失败返回-1 */ int buffer_export(int v4lfd, enum v4l2_buf_type bt, int index, int *dmafd) { struct v4l2_exportbuffer expbuf; memset(&expbuf, 0, sizeof(expbuf)); expbuf.type = bt; expbuf.index = index; if (ioctl(v4lfd, VIDIOC_EXPBUF, &expbuf) == -1) { perror("VIDIOC_EXPBUF"); return -1; } *dmafd = expbuf.fd; return 0; } /* * buffer_export_mp: 导出single-planar格式的mmap类型缓冲区内存 * v4lfd: V4L2设备文件描述符 * bt: 缓冲区类型 * index: 要导出的缓冲区序号 * n_planes: 要导出缓冲区的plane个数 * dmafd[OUT]: 返回导出的dmabuf文件描述符数组 * 返回值: 成功返回0，失败返回-1 */ int buffer_export_mp(int v4lfd, enum v4l2_buf_type bt, int index, int dmafd[], int n_planes) { int i = 0; // 逐个plane导出 for (i = 0; i < n_planes; ++i) { struct v4l2_exportbuffer expbuf; memset(&expbuf, 0, sizeof(expbuf)); expbuf.type = bt; expbuf.index = index; expbuf.plane = i; if (ioctl(v4lfd, VIDIOC_EXPBUF, &expbuf) == -1) { perror("VIDIOC_EXPBUF"); while (i) close(dmafd[--i]); return -1; } dmafd[i] = expbuf.fd; } return 0; } int main(void) { int fd = 0; int ret = 0; int i = 0; // 打开设备节点 fd = open("/dev/video4", O_RDWR); if (fd < 0) { perror("opend device error"); return -1; } printf("fd = %d\n\n", fd); // 获取设备能力 struct v4l2_capability cap; CLEAR(cap); ret = ioctl(fd, VIDIOC_QUERYCAP, &cap); if (ret < 0) { perror("VIDIOC_QUERYCAP error"); goto err; } printf("======== uvc_camera capability =========\n"); printf("driver = %s\n", cap.driver); printf("card = %s\n", cap.card); printf("bus_info = %s\n", cap.bus_info); printf("version = %u.%u.%u\n", (cap.version >> 16) & 0xFF, (cap.version >> 8) & 0xFF, cap.version & 0xFF); printf("capability = 0x%x\n", cap.capabilities); printf("device_caps = 0x%x\n", cap.device_caps); printf("========================================\n\n"); if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) { printf("%s is not a video capture device\n\n", cap.card); goto err; } if (!(cap.capabilities & V4L2_CAP_READWRITE)) printf("%s does not support read/write io\n\n", cap.card); if (!(cap.capabilities & V4L2_CAP_STREAMING)) printf("%s does not support stream io\n\n", cap.card); // 枚举设备格式 struct v4l2_fmtdesc fmtdesc; CLEAR(fmtdesc); fmtdesc.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; i = 0; printf("======== uvc_camera V4L2_BUF_TYPE_VIDEO_CAPTURE format ========\n"); while (1) { fmtdesc.index = i++; ret = ioctl(fd, VIDIOC_ENUM_FMT, &fmtdesc); if (ret < 0) { if (errno != EINVAL) { perror("VIDIOC_ENUM_FMT error"); goto err; } else { printf("enumerate end\n"); break; } } printf("index = %d\n", fmtdesc.index); printf("type = %d\n", fmtdesc.type); printf("flags = 0x%x\n", fmtdesc.flags); printf("description = %s\n", fmtdesc.description); printf("pixelformat = %c.%c.%c.%c\n\n", fmtdesc.pixelformat & 0xFF, (fmtdesc.pixelformat >> 8) & 0xFF, (fmtdesc.pixelformat >> 16) & 0xFF, (fmtdesc.pixelformat >> 24) & 0xFF); } printf("===============================================================\n\n"); // 枚举指定格式的分辨率 struct v4l2_frmsizeenum frmsize; CLEAR(frmsize); frmsize.type = V4L2_BUF_TYPE_VIDEO_CAPTURE; frmsize.pixel_format = V4L2_PIX_FMT_MJPEG; i = 0; printf("======== uvc_camera V4L2_PIX_FMT_MJPEG framesize ========\n"); while (1) { frmsize.index = i++; ret = ioctl(fd, VIDIOC_ENUM_FRAMESIZES, &frmsize); if (ret < 0) { if (errno != EINVAL) { perror("VIDIOC_ENUM_FRAMESIZES error"); goto err; } else { printf("enumerate end\n"); break; } } printf("index = %d\n", frmsize.index); switch (frmsize.type) { case V4L2_FRMSIZE_TYPE_DISCRETE: printf("V4L2_FRMSIZE_TYPE_DISCRETE\n"); break; case V4L2_FRMSIZE_TYPE_CONTINUOUS: printf("V4L2_FRMSIZE_TYPE_CONTINUOUS\n"); break; case V4L2_FRMSIZE_TYPE_STEPWISE: printf("V4L2_FRMSIZE_TYPE_STEPWISE\n"); break; default: printf("invalid type\n"); break; } if (frmsize.type == V4L2_FRMSIZE_TYPE_DISCRETE) { printf("width = %d\n", frmsize.discrete.width); printf("height = %d\n\n", frmsize.discrete.height); } else if (frmsize.type == V4L2_FRMSIZE_TYPE_STEPWISE || frmsize.type == V4L2_FRMSIZE_TYPE_CONTINUOUS) { printf("min_width = %d\n", frmsize.stepwise.min_width); pr