Fix common misspellings

[linux-2.6-block.git] / Documentation / video4linux / v4l2-framework.txt

diff --git a/Documentation/video4linux/v4l2-framework.txt b/Documentation/video4linux/v4l2-framework.txt
index 1c8d4492f5c72a4be07245d978a6b3fb056f8f3f..cf21f7aae976a903b43b7d12a69855acfef101e0 100644 (file)
--- a/Documentation/video4linux/v4l2-framework.txt
+++ b/Documentation/video4linux/v4l2-framework.txt
@@ -181,6 +181,21 @@ static int __devinit drv_probe(struct pci_dev *pdev,
        state->instance = atomic_inc_return(&drv_instance) - 1;
 }
 
+If you have multiple device nodes then it can be difficult to know when it is
+safe to unregister v4l2_device. For this purpose v4l2_device has refcounting
+support. The refcount is increased whenever video_register_device is called and
+it is decreased whenever that device node is released. When the refcount reaches
+zero, then the v4l2_device release() callback is called. You can do your final
+cleanup there.
+
+If other device nodes (e.g. ALSA) are created, then you can increase and
+decrease the refcount manually as well by calling:
+
+void v4l2_device_get(struct v4l2_device *v4l2_dev);
+
+or:
+
+int v4l2_device_put(struct v4l2_device *v4l2_dev);
 
 struct v4l2_subdev
 ------------------
@@ -328,7 +343,7 @@ ignored. If you want to check for errors use this:
        err = v4l2_device_call_until_err(v4l2_dev, 0, core, g_chip_ident, &chip);
 
 Any error except -ENOIOCTLCMD will exit the loop with that error. If no
-errors (except -ENOIOCTLCMD) occured, then 0 is returned.
+errors (except -ENOIOCTLCMD) occurred, then 0 is returned.
 
 The second argument to both calls is a group ID. If 0, then all subdevs are
 called. If non-zero, then only those whose group ID match that value will
@@ -562,6 +577,10 @@ You should also set these fields:
   (cx8802). Since the v4l2_device cannot be associated with a particular
   PCI device it is setup without a parent device. But when the struct
   video_device is setup you do know which parent PCI device to use.
+- flags: optional. Set to V4L2_FL_USE_FH_PRIO if you want to let the framework
+  handle the VIDIOC_G/S_PRIORITY ioctls. This requires that you use struct
+  v4l2_fh. Eventually this flag will disappear once all drivers use the core
+  priority handling. But for now it has to be set explicitly.
 
 If you use v4l2_ioctl_ops, then you should set .unlocked_ioctl to video_ioctl2
 in your v4l2_file_operations struct.
@@ -760,7 +779,8 @@ struct v4l2_fh
 
 struct v4l2_fh provides a way to easily keep file handle specific data
 that is used by the V4L2 framework. New drivers must use struct v4l2_fh
-since it is also used to implement priority handling (VIDIOC_G/S_PRIORITY).
+since it is also used to implement priority handling (VIDIOC_G/S_PRIORITY)
+if the video_device flag V4L2_FL_USE_FH_PRIO is also set.
 
 The users of v4l2_fh (in the V4L2 framework, not the driver) know
 whether a driver uses v4l2_fh as its file->private_data pointer by