path: root/v4l2_by-path.patch

From f19d4c3f3cd630f676d07e889e25e7c9250cfddc Mon Sep 17 00:00:00 2001
From: Grzegorz Godlewski <gg@gitgis.com>
Date: Mon, 16 May 2022 18:29:16 +0200
Subject: [PATCH] linux-v4l2: Save device by id or path

---
 plugins/linux-v4l2/v4l2-input.c | 208 +++++++++++++++++++++++---------
 1 file changed, 151 insertions(+), 57 deletions(-)

diff --git a/plugins/linux-v4l2/v4l2-input.c b/plugins/linux-v4l2/v4l2-input.c
index 9b931ea88113..8e98ea469b46 100644
--- a/plugins/linux-v4l2/v4l2-input.c
+++ b/plugins/linux-v4l2/v4l2-input.c
@@ -69,6 +69,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 struct v4l2_data {
 	/* settings */
 	char *device_id;
+	char *real_path;
 	int input;
 	int pixfmt;
 	int standard;
@@ -344,37 +345,71 @@ static void v4l2_props_set_enabled(obs_properties_t *props,
 }
 
 /*
- * List available devices
+ * Get capabilities of device
  */
-static void v4l2_device_list(obs_property_t *prop, obs_data_t *settings)
+static bool get_device_capabilities(char *dev_name,
+				    struct v4l2_capability *video_cap)
+{
+	int fd;
+	uint32_t caps;
+	if ((fd = v4l2_open(dev_name, O_RDWR | O_NONBLOCK)) == -1) {
+		const char *errstr = strerror(errno);
+		blog(LOG_WARNING, "Unable to open %s: %s", dev_name, errstr);
+		return false;
+	}
+
+	if (v4l2_ioctl(fd, VIDIOC_QUERYCAP, video_cap) == -1) {
+		blog(LOG_WARNING, "Failed to query capabilities for %s",
+		     dev_name);
+		v4l2_close(fd);
+		return false;
+	}
+	v4l2_close(fd);
+
+#ifndef V4L2_CAP_DEVICE_CAPS
+	caps = video_cap->capabilities;
+#else
+	/* ... since Linux 3.3 */
+	caps = (video_cap->capabilities & V4L2_CAP_DEVICE_CAPS)
+		       ? video_cap->device_caps
+		       : video_cap->capabilities;
+#endif
+
+	if (!(caps & V4L2_CAP_VIDEO_CAPTURE)) {
+		blog(LOG_WARNING, "%s seems to not support video capture",
+		     dev_name);
+		return false;
+	}
+
+	return true;
+}
+
+/*
+ * Build list of video devices available at path
+ */
+static void v4l2_device_add_devices_from(obs_property_t *prop,
+					 const char *basedir,
+					 bool allow_duplicates)
 {
 	DIR *dirp;
 	struct dirent *dp;
 	struct dstr device;
-	bool cur_device_found;
-	size_t cur_device_index;
-	const char *cur_device_name;
 
 #ifdef __FreeBSD__
-	dirp = opendir("/dev");
+	dirp = opendir(basedir);
 #else
-	dirp = opendir("/sys/class/video4linux");
+	if (0 == strcmp("/dev/", basedir)) {
+		dirp = opendir("/sys/class/video4linux");
+	} else {
+		dirp = opendir(basedir);
+	}
 #endif
 	if (!dirp)
 		return;
 
-	cur_device_found = false;
-	cur_device_name = obs_data_get_string(settings, "device_id");
-
-	obs_property_list_clear(prop);
-
-	dstr_init_copy(&device, "/dev/");
+	dstr_init(&device);
 
 	while ((dp = readdir(dirp)) != NULL) {
-		int fd;
-		uint32_t caps;
-		struct v4l2_capability video_cap;
-
 #ifdef __FreeBSD__
 		if (strstr(dp->d_name, "video") == NULL)
 			continue;
@@ -383,51 +418,87 @@ static void v4l2_device_list(obs_property_t *prop, obs_data_t *settings)
 		if (dp->d_type == DT_DIR)
 			continue;
 
-		dstr_resize(&device, 5);
+		dstr_copy(&device, basedir);
 		dstr_cat(&device, dp->d_name);
 
-		if ((fd = v4l2_open(device.array, O_RDWR | O_NONBLOCK)) == -1) {
-			blog(LOG_INFO, "Unable to open %s", device.array);
+		struct v4l2_capability video_cap;
+		if (!get_device_capabilities(device.array, &video_cap)) {
 			continue;
 		}
 
-		if (v4l2_ioctl(fd, VIDIOC_QUERYCAP, &video_cap) == -1) {
-			blog(LOG_INFO, "Failed to query capabilities for %s",
-			     device.array);
-			v4l2_close(fd);
-			continue;
+		bool device_already_added = false;
+
+		if (!allow_duplicates) {
+			size_t listidx = 0;
+			const char *item_name;
+			while (NULL != (item_name = obs_property_list_item_name(
+						prop, listidx++))) {
+				if (NULL !=
+				    strstr(item_name, video_cap.bus_info)) {
+					device_already_added = true;
+					break;
+				}
+			}
 		}
 
-#ifndef V4L2_CAP_DEVICE_CAPS
-		caps = video_cap.capabilities;
+		if (!device_already_added) {
+			char unique_device_name[PATH_MAX];
+			if (0 == strcmp("/dev/v4l/by-path/", basedir)) {
+				snprintf(unique_device_name, PATH_MAX,
+					 "Bus: %s (%s)", video_cap.bus_info,
+					 video_cap.card);
+			} else {
+				snprintf(unique_device_name, PATH_MAX,
+					 "%s (%s)", video_cap.card,
+					 video_cap.bus_info);
+			}
+			obs_property_list_add_string(prop, unique_device_name,
+						     device.array);
+			blog(LOG_INFO, "Found device '%s' at %s",
+			     video_cap.card, device.array);
+		}
+	}
+
+	closedir(dirp);
+	dstr_free(&device);
+}
+
+/*
+ * List available devices
+ */
+static void v4l2_device_list(obs_property_t *prop, obs_data_t *settings)
+{
+	bool cur_device_found;
+	size_t cur_device_index;
+	const char *cur_device_name;
+
+	obs_property_list_clear(prop);
+
+#ifdef __FreeBSD__
+	v4l2_device_add_devices_from(prop, "/dev/", false);
 #else
-		/* ... since Linux 3.3 */
-		caps = (video_cap.capabilities & V4L2_CAP_DEVICE_CAPS)
-			       ? video_cap.device_caps
-			       : video_cap.capabilities;
+	v4l2_device_add_devices_from(prop, "/dev/v4l/by-id/", true);
+	obs_property_list_item_disable(
+		prop,
+		obs_property_list_add_string(
+			prop,
+			"Advanced. Select device by connection:", "by_path"),
+		true);
+	v4l2_device_add_devices_from(prop, "/dev/v4l/by-path/", true);
+	v4l2_device_add_devices_from(prop, "/dev/", false);
 #endif
 
-		if (!(caps & V4L2_CAP_VIDEO_CAPTURE)) {
-			blog(LOG_INFO, "%s seems to not support video capture",
-			     device.array);
-			v4l2_close(fd);
-			continue;
-		}
+	cur_device_found = false;
+	cur_device_name = obs_data_get_string(settings, "device_id");
 
-		/* make sure device names are unique */
-		char unique_device_name[68];
-		sprintf(unique_device_name, "%s (%s)", video_cap.card,
-			video_cap.bus_info);
-		obs_property_list_add_string(prop, unique_device_name,
-					     device.array);
-		blog(LOG_INFO, "Found device '%s' at %s", video_cap.card,
-		     device.array);
-
-		/* check if this is the currently used device */
-		if (cur_device_name && !strcmp(cur_device_name, device.array))
+	size_t listidx = 0;
+	const char *item_name;
+	while (NULL !=
+	       (item_name = obs_property_list_item_string(prop, listidx++))) {
+		if (0 == strcmp(item_name, cur_device_name)) {
 			cur_device_found = true;
-
-		v4l2_close(fd);
+			break;
+		}
 	}
 
 	/* add currently selected device if not present, but disable it ... */
@@ -436,9 +507,6 @@ static void v4l2_device_list(obs_property_t *prop, obs_data_t *settings)
 			prop, cur_device_name, cur_device_name);
 		obs_property_list_item_disable(prop, cur_device_index, true);
 	}
-
-	closedir(dirp);
-	dstr_free(&device);
 }
 
 /*
@@ -795,12 +863,19 @@ static void device_added(void *vptr, calldata_t *calldata)
 	const char *dev;
 	calldata_get_string(calldata, "device", &dev);
 
-	if (strcmp(data->device_id, dev))
+	char *real_path = realpath(data->device_id, NULL);
+
+	if (real_path == NULL)
 		return;
+	if (strcmp(real_path, dev))
+		goto fail;
 
-	blog(LOG_INFO, "Device %s reconnected", dev);
+	blog(LOG_INFO, "Device %s reconnected, is opened as %s", dev,
+	     data->device_id);
 
 	v4l2_init(data);
+fail:
+	free(real_path);
 }
 /**
  * Device removed callback
@@ -816,10 +891,13 @@ static void device_removed(void *vptr, calldata_t *calldata)
 	const char *dev;
 	calldata_get_string(calldata, "device", &dev);
 
-	if (strcmp(data->device_id, dev))
+	if (data->real_path == NULL)
+		return;
+	if (strcmp(data->real_path, dev))
 		return;
 
-	blog(LOG_INFO, "Device %s disconnected", dev);
+	blog(LOG_INFO, "Device %s disconnected, was opened as %s", dev,
+	     data->device_id);
 
 	v4l2_terminate(data);
 }
@@ -965,12 +1043,23 @@ static void v4l2_init(struct v4l2_data *data)
 	int fps_num, fps_denom;
 
 	blog(LOG_INFO, "Start capture from %s", data->device_id);
+	if (data->real_path) {
+		bfree(data->real_path);
+		data->real_path = NULL;
+	}
 	data->dev = v4l2_open(data->device_id, O_RDWR | O_NONBLOCK);
 	if (data->dev == -1) {
 		blog(LOG_ERROR, "Unable to open device");
 		goto fail;
 	}
 
+	char *real_path = realpath(data->device_id, NULL);
+	if (NULL != real_path) {
+		data->real_path = real_path;
+	} else {
+		data->real_path = bstrdup(data->device_id);
+	}
+
 	/* set input */
 	if (v4l2_set_input(data->dev, &data->input) < 0) {
 		blog(LOG_ERROR, "Unable to set input %d", data->input);
@@ -1135,6 +1224,11 @@ static void v4l2_update(void *vptr, obs_data_t *settings)
 	if (data->device_id)
 		bfree(data->device_id);
 
+	if (data->real_path) {
+		bfree(data->real_path);
+		data->real_path = NULL;
+	}
+
 	data->device_id = bstrdup(obs_data_get_string(settings, "device_id"));
 	data->input = obs_data_get_int(settings, "input");
 	data->pixfmt = obs_data_get_int(settings, "pixelformat");