Determine chip from watcher callback
BGodding opened this issue · comments
I am working on an application that can be configured on runtime to send GPIO events to an external service.
I would like to use a single generic callback for all line change events across multiple chips, but as far as I can tell LineEvent and LineInfoChangeEvent do not provide a way in which to determine the source chip of the event, only the index of the line. I think the only workaround I found was to set a unique consumer for each chip and read that from the LineInfo and line names are unset.
Would there be any hesitation to adding chip name to the event change callback structs? I would be happy to submit a PR if there is not opposition.
Most callbacks do not require the chip so adding it in all cases is wasteful.
I wouldn't use a single generic callback, I would provide a callback for each request/chip that decorator the event with whatever additional info you want and passes it on to your external service.
Thank you for the reply, potential performance impact was the drawback I saw as well.
The issue is I don't know prior to compilation time how many chips are present. Could be 1 or 3 or more. I could create a large number of callbacks and hope that covers any amount of chips I run into but that did not seem idiomatic.
Another issue is that you want to decorate with chip name, but someone else might want line name or their own identifier.
I would dynamically create a closure that performs the decoration and then calls your single generic callback. That would be per chip (for LineInfoChangeEvents) or per line request (for LineEvents). That does not require foreknowledge of the number of chips or line requests and seems more idiomatic to me than insisting on a single generic callback.
That is a great idea and what I ended up doing. Cheers.