From: Marty K. <mrk...@co...> - 2010-02-09 16:00:28
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Ralph Lange wrote: > On Tue 09 Feb 2010 7:11:44 Marty Kraimer wrote: > >> Benjamin Franksen wrote: >> >> >>> On Montag, 8. Februar 2010, Ralph Lange wrote: >>> >>> >>> >>>> - Will the roles be a bitset or an enum? What if there are fields that >>>> fit multiple of your suggested default roles, e.g. the VAL field of a >>>> waveform that is used for input and output? We need a decision if the >>>> field roles are a bitset or an enum. If enum, more roles have to be >>>> added reflecting possible combinations of roles. If bitset, the >>>> interface has to be changed accordingly. >>>> >>>> >> But is the same record instance both input and output? >> >> > > Yes. > Any output that is connected to a hardware that is capable of a > multi-master setup, e.g. a field bus based actuator with other bus nodes > (PLC, SCADA) that can control the same thing, has to be bi-directional, > i.e. send values when the EPICS db changes, and update the EPICS db when > the hardware sends updates. > Several existing V3 device supports implement this. > > But in that case the database developer knows this. The developer assigns the role userSet. The hardware support may also change the fields but hardware support is not subject to access security. > Also the V3 lack of a waveform output record has lead to a few device > supports that use the existing waveform either for output or for > bi-directional behaviour. > > And again this is not a problem for PVData because the role can be assigned on a field instance basis. So I still say single role per field. Marty |