live: Fix video output localization

As V4L2 subdevice nodes use the V4L2 video device nodes major number,
there is no 1:1 correspondance between video device nodes numbers and
video device nodes minors. The video output device localization code
will thus fail if the omap3_isp driver is loaded before the omap_vout
driver.

Fix this by reading the video output device major and minor numbers from
sysfs and match them against the device node.

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

1 files changed, 31 insertions, 5 deletions

diff --git a/live.c b/live.c
index f886fa5..70e4db5 100644
--- a/live.c
+++ b/live.c
@@ -21,6 +21,7 @@
  */
 
 #define _BSD_SOURCE
+#include <ctype.h>
 #include <dirent.h>
 #include <endian.h>
 #include <errno.h>
@@ -257,12 +258,16 @@ static struct video_out_operations vo_ops = {
 static const char *video_out_find(void)
 {
 	unsigned int video_idx = 256;
-	static char devname[14];
+	static char devname[36];
+	static char dev[20];
+	unsigned int major;
+	unsigned int minor;
 	struct stat devstat;
 	struct dirent *ent;
 	char *end;
 	DIR *dir;
 	int ret;
+	int fd;
 
 	dir = opendir("/sys/bus/platform/devices/omap_vout/video4linux");
 	if (dir == NULL)
@@ -287,15 +292,36 @@ static const char *video_out_find(void)
 	if (video_idx == 256)
 		return NULL;
 
+	/* Read the device major and minor from sysfs. */
+	sprintf(devname, "/sys/class/video4linux/video%u/dev", video_idx);
+	fd = open(devname, O_RDONLY);
+	if (fd == -1)
+		return NULL;
+
+	ret = read(fd, dev, sizeof dev - 1);
+	close(fd);
+	if (ret < 0)
+		return NULL;
+
+	dev[ret] = '\0';
+	major = strtoul(dev, &end, 10);
+	if (*end != ':')
+		return NULL;
+
+	minor = strtoul(end + 1, &end, 10);
+	if (!isspace(*end) && end != '\0')
+		return NULL;
+
+	/* Verify that the device node exists. udev might have reordered the
+	 * device nodes, make sure the major/minor match as a sanity check. We
+	 * should really use libudev.
+	 */
 	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)
+	if (major(devstat.st_rdev) != major || minor(devstat.st_rdev) != minor)
 		return NULL;
 
 	return devname;