live: Locate the video output device node automatically

Iterate through the omap_vout video nodes and use the one with the
lowest minor as the video output device.

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

1 files changed, 58 insertions, 1 deletions

diff --git a/live.c b/live.c
index bd97036..c102893 100644
--- a/live.c
+++ b/live.c
@@ -21,6 +21,7 @@
  */
 
 #define _BSD_SOURCE
+#include <dirent.h>
 #include <endian.h>
 #include <errno.h>
 #include <fcntl.h>
@@ -36,7 +37,9 @@
 #include <sys/ioctl.h>
 #include <sys/mman.h>
 #include <sys/select.h>
+#include <sys/stat.h>
 #include <sys/time.h>
+#include <sys/types.h>
 
 #include <linux/fb.h>
 #include <linux/spi/spidev.h>
@@ -235,6 +238,53 @@ static struct video_out_operations vo_ops = {
 	.unwatch_fd = events_unwatch_fd,
 };
 
+static const char *video_out_find(void)
+{
+	unsigned int video_idx = 256;
+	static char devname[14];
+	struct stat devstat;
+	struct dirent *ent;
+	char *end;
+	DIR *dir;
+	int ret;
+
+	dir = opendir("/sys/bus/platform/devices/omap_vout/video4linux");
+	if (dir == NULL)
+		return NULL;
+
+	while ((ent = readdir(dir)) != NULL) {
+		unsigned int idx;
+
+		if (strncmp(ent->d_name, "video", 5))
+			continue;
+
+		idx = strtoul(ent->d_name + 5, &end, 10);
+		if (*end != '\0')
+			continue;
+
+		if (idx < video_idx)
+			video_idx = idx;
+	}
+
+	closedir(dir);
+
+	if (video_idx == 256)
+		return NULL;
+
+	sprintf(devname, "/dev/video%u", video_idx);
+	ret = stat(devname, &devstat);
+	if (ret < 0)
+		return NULL;
+
+	/* 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) != 81 || minor(devstat.st_rdev) != video_idx)
+		return NULL;
+
+	return devname;
+}
+
 /* -----------------------------------------------------------------------------
  * Frame buffer
  */
@@ -320,6 +370,7 @@ int main(int argc __attribute__((__unused__)), char *argv[] __attribute__((__unu
 	unsigned int count = 0;
 	struct v4l2_rect rect;
 	int exit_code = EXIT_FAILURE;
+	const char *vo_devname;
 	float fps;
 	int ret;
 	int c;
@@ -373,7 +424,13 @@ int main(int argc __attribute__((__unused__)), char *argv[] __attribute__((__unu
 	       view_format.code, view_format.width, view_format.height);
 
 	/* Initialize video output. */
-	vo = vo_init(VIDEOOUT_DEVICE, &vo_ops, rect.width, rect.height);
+	vo_devname = video_out_find();
+	if (vo_devname == NULL) {
+		printf("error: unable to find video output device\n");
+		goto cleanup;
+	}
+
+	vo = vo_init(vo_devname, &vo_ops, rect.width, rect.height);
 	if (vo == NULL) {
 		printf("error: unable to initialize video output\n");
 		goto cleanup;