path: root/Software/systemd/logind.mdwn
diff options
authordvdhrm <dvdhrm@web>2013-10-01 09:39:48 -0700
committerwww <>2013-10-01 09:39:48 -0700
commita76e1214453c4269ef0cd6305ed860e6f31d2e29 (patch)
tree2b6c555604758de85065a8b08197b444d5cbf25e /Software/systemd/logind.mdwn
parent426c54137198d4ad417dd4ca05f2f774e2552cd6 (diff)
Diffstat (limited to 'Software/systemd/logind.mdwn')
1 files changed, 32 insertions, 0 deletions
diff --git a/Software/systemd/logind.mdwn b/Software/systemd/logind.mdwn
index 923c4a02..8c9ee561 100644
--- a/Software/systemd/logind.mdwn
+++ b/Software/systemd/logind.mdwn
@@ -304,7 +304,23 @@ The **IdleHint**, **IdleSinceHint**, **IdleSinceHintMonotonic** properties encod
SetIdleHint(in b b);
Kill(in s who,
in s signal);
+ TakeControl(in b force);
+ ReleaseControl();
+ TakeDevice(in u major,
+ in u minor,
+ out h fd,
+ out b paused);
+ ReleaseDevice(in u major,
+ in u minor);
+ PauseDeviceComplete(in u major,
+ in u minor);
+ PauseDevice(u major,
+ u minor,
+ s type);
+ ResumeDevice(u major,
+ u minor,
+ h fd);
@@ -346,8 +362,24 @@ The **IdleHint**, **IdleSinceHint**, **IdleSinceHintMonotonic** properties encod
**SetIdleHint()** shall be called by the session object to update the idle state of the session, whenever it changes.
+**TakeControl()** allows a process to take exclusive managed device access-control for that session. Only one dbus-connection can be a controller for a given session at a time. If the **force** argument is set (root only), an existing controller is kicked out and replaced. Otherwise, this call fails if there is already a controller.
+Note that this call is limited to dbus-users with the effective UID set to the User of the Session or root.
+**ReleaseControl()** drops control of a given session again. Closing the dbus-connection implicitly releases control, too. See **TakeControl()** for more. This also releases all devices for the controller that were requested via **TakeDevice()**.
+**TakeDevice()** allows a session-controller to get a file-descriptor for a specific device. Pass in the major and minor numbers of the character-device and logind will return a file-descriptor for the device. Only a limited set of device-types is currently supported (but may be extended). logind automatically mutes the file-descriptor if the session is inactive and resumes it once the session gets active again. This guarantees that a session can only access session-devices if the session is active. Note that this revoke/resume mechanism is asynchronous and may happen at any given time.
+This only works on devices that are attached to the seat of the given session. A process is not required to have direct access to the device-node. logind only requires you to be the active session controller (see **TakeControl()**). Also note that any device can only be requested once. As long as you don't release it, further **TakeDevice()** calls will fail.
+**ReleaseDevice()** releases a device again (see **TakeDevice()**). This is also implicitly done by **ReleaseControl()** or when closing the dbus-connection.
+**PauseDeviceComplete()** allows a session-controller to synchronously pause a device after receiving a **PauseDevice("pause")** signal. Forced signals (or after an internal timeout) are automatically completed by logind asynchronously.
### Signals
+The active session-controller exclusively gets **PauseDevice** and **ResumeDevice** events for any device it requested via **TakeDevice()**. They notify the controller whenever a device is paused or resumed. A device is never resumed if a session is inactive. Also note that **PauseDevice** signals are sent before the **PropertyChanged** signal for the **Active** state. The inverse is true for **ResumeDevice**. A device may remain paused for unknown reasons even though the Session is active.
+A **PauseDevice** signal carries the major/minor as arguments and a string describing the type. **force** means the device got paused by logind already and this is only an asynchronous notification. **pause** means logind tries to pause the device and grants you limited amount of time to pause it. You must respond to this via **PauseDeviceComplete()**. This synchronous pausing-mechanism is used for backwards-compatibility to VTs and logind is free to not make use of it. It is also free to send a forced **PauseDevice** if you don't respond in a timely manner (or for any other reason). **gone** means the device was unplugged from the system and you will no longer get any notifications about it. There is no reason to call **ReleaseDevice()**. You may call **TakeDevice()** again if a new device gets the major+minor combination assigned.
+**ResumeDevice** is sent whenever a session is active and a device is resumed. It carries the major/minor as arguments and provides a new open file-descriptor. You should switch to the new descriptor and close the old one. They are not guaranteed to have the same underlying open-file-descriptor in the kernel (except for a limited set of device types).
Whenever **Active** or the idle state changes **PropertyChanged** signals are sent out to which clients can subscribe.
**Lock** (resp. **Unlock**) is sent when the session is asked to be screen-locked/screen-unlocked. A session manager of the session should listen to this signal and act accordingly. This signal is sent out as a result of the **Lock()** resp. **Unlock()** methods.