libmediactl: get the device name via udev

If configured with --with-libudev, the libmediactl is built with libudev
support. It allows to get the device name in right way in the modern linux
systems.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
[laurent.pinchart@ideasonboard.com: Remove media_private structure]
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

3 files changed, 105 insertions, 4 deletions

diff --git a/configure.in b/configure.in
index 9f91313..6903451 100644
--- a/configure.in
+++ b/configure.in
@@ -13,6 +13,28 @@ AC_PROG_LIBTOOL
 
 # Checks for libraries.
 
+AC_ARG_WITH([libudev],
+    AS_HELP_STRING([--with-libudev],
+        [Enable libudev to detect a device name]))
+
+AS_IF([test "x$with_libudev" = "xyes"],
+    [PKG_CHECK_MODULES(libudev, libudev, have_libudev=yes, have_libudev=no)],
+    [have_libudev=no])
+
+AS_IF([test "x$have_libudev" = "xyes"],
+    [
+        AC_DEFINE([HAVE_LIBUDEV], [], [Use libudev])
+        LIBUDEV_CFLAGS="$libudev_CFLAGS"
+        LIBUDEV_LIBS="$libudev_LIBS"
+        AC_SUBST(LIBUDEV_CFLAGS)
+        AC_SUBST(LIBUDEV_LIBS)
+    ],
+    [AS_IF([test "x$with_libudev" = "xyes"],
+        [AC_MSG_ERROR([libudev requested but not found])
+    ])
+])
+
+
 # Kernel headers path.
 AC_ARG_WITH(kernel-headers,
     [AC_HELP_STRING([--with-kernel-headers=DIR],
diff --git a/src/Makefile.am b/src/Makefile.am
index 267ea83..52628d2 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -5,6 +5,8 @@ mediactl_includedir=$(includedir)/mediactl
 mediactl_include_HEADERS = media.h subdev.h
 
 bin_PROGRAMS = media-ctl
+media_ctl_CFLAGS = $(LIBUDEV_CFLAGS)
+media_ctl_LDFLAGS = $(LIBUDEV_LIBS)
 media_ctl_SOURCES = main.c options.c options.h tools.h
 media_ctl_LDADD = libmediactl.la libv4l2subdev.la
 
diff --git a/src/media.c b/src/media.c
index 30d603b..099e77e 100644
--- a/src/media.c
+++ b/src/media.c
@@ -17,6 +17,8 @@
  * with this program; if not, write to the Free Software Foundation, Inc.,
  */
 
+#include "config.h"
+
 #include <sys/ioctl.h>
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -245,6 +247,69 @@ static int media_enum_links(struct media_device *media)
 	return ret;
 }
 
+#ifdef HAVE_LIBUDEV
+
+#include <libudev.h>
+
+static inline int media_udev_open(struct udev **udev)
+{
+	*udev = udev_new();
+	if (*udev == NULL)
+		return -ENOMEM;
+	return 0;
+}
+
+static inline void media_udev_close(struct udev *udev)
+{
+	if (udev != NULL)
+		udev_unref(udev);
+}
+
+static int media_get_devname_udev(struct udev *udev,
+		struct media_entity *entity, int verbose)
+{
+	struct udev_device *device;
+	dev_t devnum;
+	const char *p;
+	int ret = -ENODEV;
+
+	if (udev == NULL)
+		return -EINVAL;
+
+	devnum = makedev(entity->info.v4l.major, entity->info.v4l.minor);
+	if (verbose)
+		printf("looking up device: %u:%u\n", major(devnum), minor(devnum));
+	device = udev_device_new_from_devnum(udev, 'c', devnum);
+	if (device) {
+		p = udev_device_get_devnode(device);
+		if (p) {
+			strncpy(entity->devname, p, sizeof(entity->devname));
+			entity->devname[sizeof(entity->devname) - 1] = '\0';
+		}
+		ret = 0;
+	}
+
+	udev_device_unref(device);
+
+	return ret;
+}
+
+#else	/* HAVE_LIBUDEV */
+
+struct udev;
+
+static inline int media_udev_open(struct udev **udev) { return 0; }
+
+static inline void media_udev_close(struct udev *udev) { }
+
+static inline int media_get_devname_udev(struct udev *udev,
+		struct media_entity *entity, int verbose)
+{
+	return -ENOTSUP;
+}
+
+#endif	/* HAVE_LIBUDEV */
+
 static int media_get_devname_sysfs(struct media_entity *entity)
 {
 	struct stat devstat;
@@ -281,14 +346,19 @@ static int media_get_devname_sysfs(struct media_entity *entity)
 	return 0;
 }
 
-static int media_enum_entities(struct media_device *media)
+static int media_enum_entities(struct media_device *media, int verbose)
 {
 	struct media_entity *entity;
+	struct udev *udev;
 	unsigned int size;
 	__u32 id;
-	int ret = 0;
+	int ret;
 
-	for (id = 0; ; id = entity->info.id) {
+	ret = media_udev_open(&udev);
+	if (ret < 0)
+		printf("%s: Can't get udev context\n", __func__);
+
+	for (id = 0, ret = 0; ; id = entity->info.id) {
 		size = (media->entities_count + 1) * sizeof(*media->entities);
 		media->entities = realloc(media->entities, size);
 
@@ -323,9 +393,15 @@ static int media_enum_entities(struct media_device *media)
 		    media_entity_type(entity) != MEDIA_ENT_T_V4L2_SUBDEV)
 			continue;
 
+		/* Try to get the device name via udev */
+		if (!media_get_devname_udev(udev, entity, verbose))
+			continue;
+
+		/* Fall back to get the device name via sysfs */
 		media_get_devname_sysfs(entity);
 	}
 
+	media_udev_close(udev);
 	return ret;
 }
 
@@ -353,7 +429,8 @@ struct media_device *media_open(const char *name, int verbose)
 	if (verbose)
 		printf("Enumerating entities\n");
 
-	ret = media_enum_entities(media);
+	ret = media_enum_entities(media, verbose);
+
 	if (ret < 0) {
 		printf("%s: Unable to enumerate entities for device %s (%s)\n",
 			__func__, name, strerror(-ret));