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author | Linus Torvalds <torvalds@linux-foundation.org> | 2011-07-30 00:08:53 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-07-30 00:08:53 -0700 |
commit | 664a41b8a91bf78a01a751e15175e0008977685a (patch) | |
tree | d9dc15c83400ad2dfb430ff27ae3e7fdc9395856 /Documentation/DocBook/media/v4l/dev-event.xml | |
parent | 983236b5741e557451f3ed4ec5ebf1f62a5b2c15 (diff) | |
parent | ee2ce3a0b43d14d792d34cf88e7bc2091096744b (diff) | |
download | blackbird-op-linux-664a41b8a91bf78a01a751e15175e0008977685a.tar.gz blackbird-op-linux-664a41b8a91bf78a01a751e15175e0008977685a.zip |
Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6
* 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6: (430 commits)
[media] ir-mce_kbd-decoder: include module.h for its facilities
[media] ov5642: include module.h for its facilities
[media] em28xx: Fix DVB-C maxsize for em2884
[media] tda18271c2dd: Fix saw filter configuration for DVB-C @6MHz
[media] v4l: mt9v032: Fix Bayer pattern
[media] V4L: mt9m111: rewrite set_pixfmt
[media] V4L: mt9m111: fix missing return value check mt9m111_reg_clear
[media] V4L: initial driver for ov5642 CMOS sensor
[media] V4L: sh_mobile_ceu_camera: fix Oops when USERPTR mapping fails
[media] V4L: soc-camera: remove soc-camera bus and devices on it
[media] V4L: soc-camera: un-export the soc-camera bus
[media] V4L: sh_mobile_csi2: switch away from using the soc-camera bus notifier
[media] V4L: add media bus configuration subdev operations
[media] V4L: soc-camera: group struct field initialisations together
[media] V4L: soc-camera: remove now unused soc-camera specific PM hooks
[media] V4L: pxa-camera: switch to using standard PM hooks
[media] NetUP Dual DVB-T/C CI RF: force card hardware revision by module param
[media] Don't OOPS if videobuf_dvb_get_frontend return NULL
[media] NetUP Dual DVB-T/C CI RF: load firmware according card revision
[media] omap3isp: Support configurable HS/VS polarities
...
Fix up conflicts:
- arch/arm/mach-omap2/board-rx51-peripherals.c:
cleanup regulator supply definitions in mach-omap2
vs
OMAP3: RX-51: define vdds_csib regulator supply
- drivers/staging/tm6000/tm6000-alsa.c (trivial)
Diffstat (limited to 'Documentation/DocBook/media/v4l/dev-event.xml')
-rw-r--r-- | Documentation/DocBook/media/v4l/dev-event.xml | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/Documentation/DocBook/media/v4l/dev-event.xml b/Documentation/DocBook/media/v4l/dev-event.xml new file mode 100644 index 000000000000..f14ae3fe107c --- /dev/null +++ b/Documentation/DocBook/media/v4l/dev-event.xml @@ -0,0 +1,51 @@ + <title>Event Interface</title> + + <para>The V4L2 event interface provides a means for a user to get + immediately notified on certain conditions taking place on a device. + This might include start of frame or loss of signal events, for + example. Changes in the value or state of a V4L2 control can also be + reported through events. + </para> + + <para>To receive events, the events the user is interested in first must + be subscribed using the &VIDIOC-SUBSCRIBE-EVENT; ioctl. Once an event is + subscribed, the events of subscribed types are dequeueable using the + &VIDIOC-DQEVENT; ioctl. Events may be unsubscribed using + VIDIOC_UNSUBSCRIBE_EVENT ioctl. The special event type V4L2_EVENT_ALL may + be used to unsubscribe all the events the driver supports.</para> + + <para>The event subscriptions and event queues are specific to file + handles. Subscribing an event on one file handle does not affect + other file handles.</para> + + <para>The information on dequeueable events is obtained by using select or + poll system calls on video devices. The V4L2 events use POLLPRI events on + poll system call and exceptions on select system call.</para> + + <para>Starting with kernel 3.1 certain guarantees can be given with + regards to events:<orderedlist> + <listitem> + <para>Each subscribed event has its own internal dedicated event queue. +This means that flooding of one event type will not interfere with other +event types.</para> + </listitem> + <listitem> + <para>If the internal event queue for a particular subscribed event +becomes full, then the oldest event in that queue will be dropped.</para> + </listitem> + <listitem> + <para>Where applicable, certain event types can ensure that the payload +of the oldest event that is about to be dropped will be merged with the payload +of the next oldest event. Thus ensuring that no information is lost, but only an +intermediate step leading up to that information. See the documentation for the +event you want to subscribe to whether this is applicable for that event or not.</para> + </listitem> + </orderedlist></para> + + <!-- +Local Variables: +mode: sgml +sgml-parent-document: "v4l2.sgml" +indent-tabs-mode: nil +End: + --> |