tvservice: Enhance callback mechanism #162
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In some circumstances an application may register multiple callback instances using the same function pointer but differerent data context. To allow proper unregister of these callbacks add a new method which checks for function pointer and data pointer before removal. Signed-off-by: Julian Scheel <julian@jusst.de>
A maximum callback count of 2 might be too low for some usecases. Signed-off-by: Julian Scheel <julian@jusst.de>
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Looks fine. I has been meaning to increase the number of callbacks. 2 always seemed a bit mean... |
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tvservice: Enhance callback mechanism
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See: http://forum.xbmc.org/showthread.php?tid=176043&pid=1673527#pid1673527 firmware: video_decode: Allow ts fifo to be forced off with avoid_fix_ts=2 See: http://forum.xbmc.org/showthread.php?tid=148646&pid=1674875#pid1674875 userland: tvservice: Enhance callback mechanism See: raspberrypi/userland#162
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See: http://forum.xbmc.org/showthread.php?tid=176043&pid=1673527#pid1673527 firmware: video_decode: Allow ts fifo to be forced off with avoid_fix_ts=2 See: http://forum.xbmc.org/showthread.php?tid=148646&pid=1674875#pid1674875 userland: tvservice: Enhance callback mechanism See: raspberrypi/userland#162
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See: http://forum.xbmc.org/showthread.php?tid=176043&pid=1673527#pid1673527 firmware: video_decode: Allow ts fifo to be forced off with avoid_fix_ts=2 See: http://forum.xbmc.org/showthread.php?tid=148646&pid=1674875#pid1674875 userland: tvservice: Enhance callback mechanism See: raspberrypi/userland#162
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While working on our VLC mmal plugins, which use tvservice to get notified about display mode changes we ran into a small problem:
VLC might create multiple vout instances in parallel of which each one needs to register a callback to get notified about mode changes. The first problem is the limit of 2 callbacks, which may be triggered in this case. The second, even more critical one, is the unregister function which only checks the function pointer for removal of the callback list.
In our case we register the same function pointer multiple times but with different context data each. So when a vout is destroyed we need to ensure that the correct callback is unregistered, which can be done with vc_tv_unregister_callback_full as proposed in this pull requests. It simply takes the data pointer as second argument and requires a match of function and data pointer for removal.