[fpc-pascal] Access GPIO pins on RPi2 without root?

[Mark Morgan Lloyd]

Jonas Maebe wrote:
> Bo Berglund wrote on Wed, 07 Oct 2015:
> 
>> I think that it really does because there must be some interface
>> between the FPC system and the underlying operating system managing
>> the hardware.
> 
> On Linux/Unix, every interface to hardware gets exposed as a file 
> (generally under /dev). Sometimes you have libraries that provide a 
> higher level interface, but in the end it will always access that file. 
> If you need root permissions to perform actions on this file with 
> language X, you will also need them with language Y and also if you use 
> library Z to access it. The file operations are basic POSIX operations 
> (open, read, write, ioctl, close), which are available with an "fp" 
> prefix via the baseunix and unix units, and which are the same in C or 
> other languages.
> 
> If you have a library that you want to use, then you can of course ask 
> here whether anyone has translated the headers for it (which will 
> probably be in C) to Pascal or so.

I've just been taking a look and I don't immediately see a kernel module 
that provides an interface to GPIO via /dev. I think there's things for 
I2C etc.

Via 
http://wiki.freepascal.org/Lazarus_on_Raspberry_Pi#1._Native_hardware_access 
I see mention of /sys/class/gpio etc. although I've not looked to see 
what's implemented as standard. Using this interface requires membership 
of the gpio group, which in principle answers Bo's question.

-- 
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk

[Opinions above are the author's, not those of his employers or colleagues]