Use sysfs to locate devices nodes

Changes made during the v4l2_subdev API review renamed the /dev/subdev*
device nodes to /dev/v4l-subdev*. Instead of hardcoding the names in the
media-ctl application, use sysfs to retrieve the kernel device name and
assume the device node name is identical.

This isn't a perfect solution, we should really use libudev, but it will
do for now.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 24 insertions, 17 deletions

diff --git a/media.c b/media.c
index aaa1005..1bc39e1 100644
--- a/media.c
+++ b/media.c
@@ -430,9 +430,11 @@ static int media_enum_entities(struct media_device *media)
 {
 	struct media_entity *entity;
 	struct stat devstat;
-	char devname[32];
 	unsigned int size;
-	unsigned int i;
+	char devname[32];
+	char sysname[32];
+	char target[1024];
+	char *p;
 	__u32 id;
 	int ret;
 
@@ -465,24 +467,29 @@ static int media_enum_entities(struct media_device *media)
 		    (entity->info.type != MEDIA_ENTITY_TYPE_SUBDEV))
 			continue;
 
-		for (i = 0; i < 256; ++i) {
-			if (entity->info.type == MEDIA_ENTITY_TYPE_NODE)
-				sprintf(devname, "/dev/video%u", i);
-			else
-				sprintf(devname, "/dev/subdev%u", i);
+		sprintf(sysname, "/sys/dev/char/%u:%u", entity->info.v4l.major,
+			entity->info.v4l.minor);
+		ret = readlink(sysname, target, sizeof(target));
+		if (ret < 0)
+			continue;
 
-			ret = stat(devname, &devstat);
-			if (ret < 0)
-				continue;
+		target[ret] = '\0';
+		p = strrchr(target, '/');
+		if (p == NULL)
+			continue;
 
-			if (major(devstat.st_rdev) == entity->info.v4l.major &&
-			    minor(devstat.st_rdev) == entity->info.v4l.minor) {
-				strcpy(entity->devname, devname);
-				break;
-			}
-		}
+		sprintf(devname, "/dev/%s", p + 1);
+		ret = stat(devname, &devstat);
+		if (ret < 0)
+			continue;
 
-		id = entity->info.id;
+		/* Sanity check: udev might have reordered the device nodes.
+		 * Make sure the major/minor match. We should really use
+		 * libudev.
+		 */
+		if (major(devstat.st_rdev) == entity->info.v4l.major &&
+		    minor(devstat.st_rdev) == entity->info.v4l.minor)
+			strcpy(entity->devname, devname);
 	}
 
 	return 0;