From 3c3a41eb2b33ba2253eb7439ff6290c414143416 Mon Sep 17 00:00:00 2001
From: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
Date: Tue, 14 Sep 2021 07:08:22 +0200
Subject: [PATCH] Automatically detect camera capable v4l2 device.

Bug-AGL: SPEC-4148
Change-Id: I42cf0adf9e55679069992d73f079b916684f8e8b
Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com>
---
 app/main.cpp  |  4 +---
 app/utils.cpp | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 app/utils.h   |  3 +++
 3 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/app/main.cpp b/app/main.cpp
index fff9c4c..182489e 100644
--- a/app/main.cpp
+++ b/app/main.cpp
@@ -23,8 +23,6 @@
 #include <gst/video/videooverlay.h>
 #include <gst/wayland/wayland.h>
 
-#define DEFAULT_VIDEO_DEVICE	"/dev/video0"
-
 // these only applies if the window is a dialog/pop-up one
 // by default the compositor make the window maximized
 #define WINDOW_WIDTH_SIZE	640
@@ -669,7 +667,7 @@ int main(int argc, char *argv[])
 
 	memset(pipeline_str, 0, sizeof(pipeline_str));
 	snprintf(pipeline_str, sizeof(pipeline_str), "v4l2src device=%s ! video/x-raw,width=%d,height=%d ! waylandsink", 
-		DEFAULT_VIDEO_DEVICE, WINDOW_WIDTH_SIZE, WINDOW_HEIGHT_SIZE);
+		get_camera_device(), WINDOW_WIDTH_SIZE, WINDOW_HEIGHT_SIZE);
 	gst_init(&gargc, &gargv);
 
 	setbuf(stdout, NULL);
diff --git a/app/utils.cpp b/app/utils.cpp
index f1c3eae..1cf71f2 100644
--- a/app/utils.cpp
+++ b/app/utils.cpp
@@ -1,10 +1,16 @@
 #include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/ioctl.h>
 #include <unistd.h>
 #include <fcntl.h>
+#include <dirent.h>
 #include <assert.h>
 #include <cstdlib>
 #include <cstring>
 #include <cerrno>
+#include <cstdio>
+#include <cctype>
+#include <linux/videodev2.h>
 
 #include "utils.h"
 
@@ -148,3 +154,44 @@ os_create_anonymous_file(off_t size)
 
 	return fd;
 }
+
+const char*
+get_camera_device(void)
+{
+	DIR *dir = opendir("/dev");
+	if (!dir) {
+		perror("Couldn't open the '/dev' directory");
+		return NULL;
+	}
+
+	static char device[PATH_MAX];
+	bool found = false;
+	while (struct dirent *dirent = readdir(dir)) {
+		if (strncmp(dirent->d_name, "video", strlen("video")))
+			continue;
+		if (!isdigit(dirent->d_name[strlen("video")]))
+			continue;
+
+		strcpy(device, "/dev/");
+		strncat(device, dirent->d_name, sizeof(device) - 1);
+
+		int fd = open(device, O_RDWR);
+		if (fd == -1)
+			continue;
+		struct v4l2_capability vid_cap;
+		if (ioctl(fd, VIDIOC_QUERYCAP, &vid_cap) < 0) {
+			close(fd);
+			continue;
+		}
+		close(fd);
+
+		if ((vid_cap.capabilities & V4L2_CAP_VIDEO_CAPTURE) ||
+			(vid_cap.capabilities & V4L2_CAP_VIDEO_CAPTURE_MPLANE)) {
+			found = true;
+			break;
+		}
+	}
+
+	closedir(dir);
+	return found ? device : NULL;
+}
diff --git a/app/utils.h b/app/utils.h
index 99b2e30..8d6f0fd 100644
--- a/app/utils.h
+++ b/app/utils.h
@@ -8,6 +8,9 @@ extern "C" {
 int
 os_create_anonymous_file(off_t size);
 
+const char*
+get_camera_device(void);
+
 #ifdef  __cplusplus
 }
 #endif
-- 
2.16.6