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joan2937 / lg

Linux C libraries and Python modules for manipulating GPIO
The Unlicense
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Enumerate valid chips #20

Open EliRibble opened 1 year ago

EliRibble commented 1 year ago

It appears that the only way to determine how many chips are valid is to attempt gpiochip_open with some number of different integers and discard any failures. Is there an API to get the list of chips numbers that are valid? If not, what is the range of integers we should test?

joan2937 commented 1 year ago

The Linux kernel will assign gpiochip numbers. I assume they would be assigned in order 0, 1, 2, etc. I can think of no reason for not assigning in that order. So try opening increasing numbers until there is a failure.

However that is my assumption. I do not know if the kernel makes any guarantee.

EliRibble commented 1 year ago

Thanks - is there a way to distinguish between "that chip does not exist" and "the chip exists, but you can't get a handle to it"?

DanielDecker commented 2 months ago

Type the following command in a the terminal to list all available gpiochips: ls /dev/gpiochip* For more details try: sudo cat /sys/kernel/debug/gpio I hope this helps!