PeterBee97 commented on code in PR #18745:
URL: https://github.com/apache/nuttx/pull/18745#discussion_r3098456445
##########
arch/sim/src/sim/posix/sim_host_v4l2.c:
##########
@@ -84,27 +88,239 @@ static int host_video_ioctl(int fd, int request, void *arg)
return r;
}
+static bool host_video_is_capture_device(const char *host_video_dev_path)
+{
+ struct v4l2_capability cap;
+ int fd;
+ bool available = false;
+
+ fd = open(host_video_dev_path, O_RDWR | O_NONBLOCK);
+ if (fd < 0)
+ {
+ fd = open(host_video_dev_path, O_RDONLY | O_NONBLOCK);
+ if (fd < 0)
+ {
+ return false;
+ }
+ }
+
+ memset(&cap, 0, sizeof(cap));
+ if (host_video_ioctl(fd, VIDIOC_QUERYCAP, &cap) == 0)
+ {
+ uint32_t capabilities = cap.device_caps != 0 ? cap.device_caps :
+ cap.capabilities;
+
+ if ((capabilities & V4L2_CAP_VIDEO_CAPTURE) != 0)
+ {
+ available = true;
+ }
+ }
+
+ close(fd);
+ return available;
+}
+
+static int host_video_get_device_path_by_index(const char *dirpath,
+ int index,
+ char *devpath,
+ size_t devpathlen)
+{
+ DIR *dir;
+ struct dirent *entry;
+ int count = 0;
+
+ dir = opendir(dirpath);
+ if (dir == NULL)
+ {
+ return -errno;
+ }
+
+ while ((entry = readdir(dir)) != NULL)
+ {
+ char path[PATH_MAX];
+
+ if (strncmp(entry->d_name, "video", 5) != 0)
+ {
+ continue;
+ }
+
+ if (snprintf(path, sizeof(path), "/dev/%s", entry->d_name) >=
+ (int)sizeof(path))
+ {
+ continue;
+ }
+
+ if (!host_video_is_capture_device(path))
+ {
+ continue;
+ }
+
+ if (count == index)
+ {
+ if (snprintf(devpath, devpathlen, "%s", path) >= devpathlen)
+ {
+ closedir(dir);
+ return -ENAMETOOLONG;
+ }
+
+ closedir(dir);
+ return 0;
+ }
+
+ count++;
+ }
+
+ closedir(dir);
+ return -ENODEV;
+}
+
+static int host_video_count_devices_in_dir(const char *dirpath)
+{
+ DIR *dir;
+ struct dirent *entry;
+ int count = 0;
+
+ dir = opendir(dirpath);
+ if (dir == NULL)
+ {
+ return -errno;
+ }
+
+ while ((entry = readdir(dir)) != NULL)
+ {
+ char devpath[PATH_MAX];
+
+ if (strncmp(entry->d_name, "video", 5) != 0)
+ {
+ continue;
+ }
+
+ if (snprintf(devpath, sizeof(devpath), "/dev/%s", entry->d_name) >=
+ (int)sizeof(devpath))
+ {
+ continue;
+ }
+
+ if (host_video_is_capture_device(devpath))
+ {
+ count++;
+ }
+ }
+
+ closedir(dir);
+ return count;
+}
+
+static int host_video_resolve_device_path(const char *host_video_dev_path,
+ char *resolved_path,
+ size_t resolved_path_len)
+{
+ const char *name;
+ char *endptr;
+ long index;
+ int ret;
+
+ name = strrchr(host_video_dev_path, '/');
+ name = name != NULL ? name + 1 : host_video_dev_path;
+
+ if (strncmp(name, "video", 5) != 0)
+ {
+ if (snprintf(resolved_path, resolved_path_len, "%s",
+ host_video_dev_path) >= (int)resolved_path_len)
+ {
+ return -ENAMETOOLONG;
+ }
+
+ return 0;
+ }
+
+ index = strtol(name + 5, &endptr, 10);
+ if (endptr == name + 5 || *endptr != '\0' || index < 0 ||
+ index > INT_MAX)
+ {
+ return -EINVAL;
+ }
+
+ ret = host_video_get_device_path_by_index("/sys/class/video4linux", index,
+ resolved_path,
+ resolved_path_len);
+ if (ret == -ENOENT || ret == -ENODEV || ret == -EINVAL)
+ {
+ ret = host_video_get_device_path_by_index("/dev", index,
+ resolved_path,
+ resolved_path_len);
+ }
+
+ if (ret < 0)
+ {
+ WARN("failed to resolve %s to host capture device: %d",
+ host_video_dev_path, ret);
+ }
+
+ return ret;
+}
+
/****************************************************************************
* Public Functions
****************************************************************************/
+int host_video_get_device_count(void)
+{
+ int count;
+
+ count = host_video_count_devices_in_dir("/sys/class/video4linux");
+ if (count >= 0)
+ {
+ return count;
+ }
+
+ count = host_video_count_devices_in_dir("/dev");
+ if (count >= 0)
+ {
+ return count;
+ }
+
+ return 0;
+}
+
bool host_video_is_available(const char *host_video_dev_path)
{
- return access(host_video_dev_path, F_OK) == 0;
+ char resolved_path[PATH_MAX];
+ int ret;
+
+ ret = host_video_resolve_device_path(host_video_dev_path, resolved_path,
Review Comment:
Because I wanted to filter-out non-capture video device. For now I have two
cameras connected, but 4 video devices under /dev in host. I intentionally
mapped /dev/video0 and /dev/video2 on host to /dev/video0 and /dev/video1 in
NuttX. Is this behavior desired or do you prefer mapping directly?
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