Datapoint Read Functions
- Rich Blomseth
You can use a datapoint read callback function to respond to a datapoint read request from IDL to a custom driver. A datapoint read request originates from an IAP/MQ datapoint read request to a custom driver. The IAP/MQ datapoint read request may be a result of periodic polling, an on-demand get request from an IAP/MQ client, event-driven monitoring, or when polling the first datapoint of a device for provisioning, a test action, or health checking. In all cases, the DpRead callback function is called by the IDL that was registered during the custom driver init process.
Datapoint Read Callback Function
DpRead
IdlErrorCodes DpRead(int callback_index, IdlDev *dev, IdlDatapoint *dp, void *idlContext); |
callback_index is a callback identifier used by IDL. The custom driver must pass it back to IDL when calling IdlDpReadResult.
dev is the IDL device object for the device containing the datapoint to read. The custom driver must pass it back to IDL when calling IdlDpReadResult.
dp is the IDL datapoint object for the datapoint to read. The custom driver must pass it back to IDL when calling IdlDpReadResult.
When a datapoint read is complete, IDI reports the result to the IDL using IdlDpReadResult.
Datapoint Read Related Functions
IdlDpReadCallbackSet
void IdlDpReadCallbackSet(Idl *idl, int (*DpRead)(int, IdlDev *, IdlDatapoint *, void *)); |
Must be called by the custom driver prior to calling IdlInit.
IdlDpReadResult
void IdlDpReadResult(int callbackIndex, IdlDev *dev, IdlDatapoint *dp, void *idlContext, int idlError, char *prioArray, double value); |
Must be called by the custom driver at the end of the callback function before exiting.
callback_index is the callback identifier received in the DpRead callback.
dev is the IDL device object for the device received in the DpRead callback.
dp is the IDL datapoint object received in the DpRead callback.
idlError is an error code as described in Error Codes.
prioArray is not used by IDL and is reserved for future use. The custom driver can send it as NULL.
value is the reported value for the datapoint. The value of the datapoint must be returned as a double value.