Warn on duplicate master releasing.
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EtherCAT master TODO
$Id$
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Important things to do:
* Read AL Status Code with AL Control Response (if possible?)
* Coupling of EoE handlers before configuring slaves.
(avoiding duplicate configuration)
* Implement all EtherCAT commands
* Determine number of frames the NIC can handle
* Implement e100 driver
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Not-so-important things to do:
* Calculate bus topology
* File access over EtherCAT (FoE)
* Allow VLAN tagging
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