[PATCH] v4l: Introduce "stream" attribute for persistent video4linux device nodes
- Date: Mon, 28 Apr 2008 00:26:55 -0700
- From: Brandon Philips <brandon@xxxxxxxx>
- Subject: [PATCH] v4l: Introduce "stream" attribute for persistent video4linux device nodes
Disclaimer: I am not attached to the name, "stream". Open to suggestion.
Kees introduced a patch set last week that attempts to get stable device naming
for v4l. The set used a string attribute called function to allow udev to
assemble a unique and stable path for device nodes.
This patch is similar. However, instead of a string an integer is used called
"stream". If the driver calls video_register_device in the same order every
time it is loaded then we can end up with something like this with the right
udev rules[1]:
/dev/v4l/by-path/pci-0000\:00\:1d.2-usb-0\:1\:1.0-video0
/dev/v4l/by-path/pci-0000\:00\:1d.2-usb-0\:1\:1.0-video1
/dev/v4l/by-path/pci-0000\:00\:1d.2-usb-0\:1\:1.0-video2
# ls -la /dev/v4l/by-path/pci-0000\:00\:1d.2-usb-0\:1\:1.0-video0
lrwxrwxrwx 1 root root 12 2008-04-28 00:02 /dev/v4l/by-path/pci-0000:00:1d.2-usb-0:1:1.0-video0 -> ../../video1
Kees: I don't have a device that creates multiple device nodes. Please
test with ivtv. :D
video_register_device_stream is available to drivers to request a specific
stream number.
Signed-off-by: Brandon Philips <bphilips@xxxxxxx>
---
[1] Place the attached udev rules in /etc/udev/rules.d/60-persistent-v4l.rules
linux/drivers/media/video/videodev.c | 96 ++++++++++++++++++++++++++++++++++-
linux/include/media/v4l2-dev.h | 4 +
2 files changed, 98 insertions(+), 2 deletions(-)
Index: v4l-dvb-clean/linux/drivers/media/video/videodev.c
===================================================================
--- v4l-dvb-clean.orig/linux/drivers/media/video/videodev.c
+++ v4l-dvb-clean/linux/drivers/media/video/videodev.c
@@ -428,6 +428,14 @@ EXPORT_SYMBOL(v4l_printk_ioctl);
* sysfs stuff
*/
+static ssize_t show_stream(struct device *cd,
+ struct device_attribute *attr, char *buf)
+{
+ struct video_device *vfd = container_of(cd, struct video_device,
+ class_dev);
+ return sprintf(buf, "%i\n", vfd->stream);
+}
+
#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,13)
static ssize_t show_name(struct class_device *cd, char *buf)
#else
@@ -486,6 +494,7 @@ static void video_release(struct device
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,13)
static struct device_attribute video_device_attrs[] = {
__ATTR(name, S_IRUGO, show_name, NULL),
+ __ATTR(stream, S_IRUGO, show_stream, NULL),
__ATTR_NULL
};
#endif
@@ -2013,8 +2022,81 @@ out:
}
EXPORT_SYMBOL(video_ioctl2);
+struct stream_number_info {
+ struct device *dev;
+ unsigned int used[VIDEO_NUM_DEVICES];
+};
+
+static int __fill_stream_number_info(struct device *cd, void *data)
+{
+ struct stream_number_info *info = data;
+ struct video_device *vfd = container_of(cd, struct video_device,
+ class_dev);
+
+ if (info->dev == vfd->dev)
+ info->used[vfd->stream] = 1;
+
+ return 0;
+}
+
+/**
+ * assign_stream_number - assign stream number based on parent device
+ * @vdev: video_device to assign stream number to, vdev->dev should be assigned
+ * @num: -1 if auto assign, requested number otherwise
+ *
+ *
+ * returns -ENFILE if num is already in use, a free stream number if
+ * successful.
+ */
+static int get_stream_number(struct video_device *vdev, int num)
+{
+ struct stream_number_info *info;
+ int i;
+ int ret = 0;
+
+ if (num >= VIDEO_NUM_DEVICES)
+ return -EINVAL;
+
+ info = kzalloc(sizeof(*info), GFP_KERNEL);
+ if (!info)
+ return -ENOMEM;
+
+ info->dev = vdev->dev;
+
+ ret = class_for_each_device(&video_class, &info,
+ __fill_stream_number_info);
+
+ if (ret < 0)
+ goto out;
+
+ if (num >= 0) {
+ if (!info->used[num])
+ ret = num;
+ else
+ ret = -ENFILE;
+
+ goto out;
+ }
+
+ for (i = 0; i < VIDEO_NUM_DEVICES; i++) {
+ if (!info->used[i])
+ ret = i;
+ goto out;
+ }
+
+out:
+ kfree(info);
+ return ret;
+}
+
static const struct file_operations video_fops;
+int video_register_device(struct video_device *vfd, int type, int nr)
+{
+ return video_register_device_stream(vfd, type, nr, -1);
+}
+EXPORT_SYMBOL(video_register_device);
+
/**
* video_register_device - register video4linux devices
* @vfd: video device structure we want to register
@@ -2040,7 +2122,8 @@ static const struct file_operations vide
* %VFL_TYPE_RADIO - A radio card
*/
-int video_register_device(struct video_device *vfd, int type, int nr)
+int video_register_device_stream(struct video_device *vfd, int type, int nr,
+ int stream)
{
int i=0;
int base;
@@ -2143,6 +2226,15 @@ int video_register_device(struct video_d
}
#endif
+ ret = get_stream_number(vfd, stream);
+ if (ret < 0) {
+ printk(KERN_ERR "%s: get_stream_number failed\n",
+ __func__);
+ goto fail_minor;
+ }
+
+ vfd->stream = ret;
+
#if 1 /* keep */
/* needed until all drivers are fixed */
if (!vfd->release)
@@ -2159,7 +2251,7 @@ fail_minor:
mutex_unlock(&videodev_lock);
return ret;
}
-EXPORT_SYMBOL(video_register_device);
+EXPORT_SYMBOL(video_register_device_stream);
/**
* video_unregister_device - unregister a video4linux device
Index: v4l-dvb-clean/linux/include/media/v4l2-dev.h
===================================================================
--- v4l-dvb-clean.orig/linux/include/media/v4l2-dev.h
+++ v4l-dvb-clean/linux/include/media/v4l2-dev.h
@@ -113,6 +113,8 @@ struct video_device
int type; /* v4l1 */
int type2; /* v4l2 */
int minor;
+ /* attribute to diferentiate multiple streams on one physical device */
+ int stream;
int debug; /* Activates debug level*/
@@ -373,6 +375,8 @@ void *priv;
/* Version 2 functions */
extern int video_register_device(struct video_device *vfd, int type, int nr);
+int video_register_device_stream(struct video_device *vfd, int type, int nr,
+ int stream);
void video_unregister_device(struct video_device *);
extern int video_ioctl2(struct inode *inode, struct file *file,
unsigned int cmd, unsigned long arg);
# do not edit this file, it will be overwritten on update
ACTION!="add|change", GOTO="persistent_v4l_end"
SUBSYSTEM!="video4linux", GOTO="persistent_v4l_end"
# check for valid "stream" number
TEST!="stream", GOTO="persistent_v4l_end"
ATTR{stream}!="?*", GOTO="persistent_v4l_end"
IMPORT{program}="path_id %p"
ENV{ID_PATH}=="?*", KERNEL=="video*", SYMLINK+="v4l/by-path/$env{ID_PATH}-video$attr{stream}"
ENV{ID_PATH}=="?*", KERNEL=="audio*", SYMLINK+="v4l/by-path/$env{ID_PATH}-audio$attr{stream}"
LABEL="persistent_v4l_end"
--
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