Tweak Python bindings to create standalone sdist package

[Gadgetoid]

⚠️ Replaced by #5
⚠️ Submitted upstream - https://lore.kernel.org/linux-gpio/20231013112812.148021-1-phil@gadgetoid.com/T/#t

This changeset vendors the gpiod library into the Python package.

This works by symlinking the lib and include directories up to the parent module, and updating MANIFEST.in to include the source files.

If "LINK_SYSTEM_LIBGPIOD =1" is not specified then the gpiod._ext C Extension is amended to include all of the C sources for gpiod, so it can be built as a standalone module without depending upon a shared distro library.

Why?

So that it can produce an sdist that is installable irrespective of the availability or version of a distro-supplied libgpiod. This prevents a libgpiod pypi package install balking because the distro libgpiod is outdated or otherwise incompatible. This happens with the currently available libgpiod on pypi.

This also ensures that libgpiod can be installed via pypi into an isolated virtual environment, specified as a dependency for Python packages and allow Python developers to target the newest API version.

Fallback to system libgpiod

Installing from an sdist with a "LINK_SYSTEM_LIBGPIOD=1" environment variable will drop the vendored library in favour of the system, however the system library must be compatible with the bindings.

Building

This package has been tested on Raspberry Pi OS (Debian Bookworm based) and Ubuntu Mantic (Pi 5 ARM64 release).

You'll need:

sudo apt install git build-essential make autoconf autoconf-archive automake pkg-config libtool
sudo apt install python3-dev python3-setuptools python3-pip python3-wheel python3-venv

Then clone this branch:

git clone https://github.com/gadgetoid/libgpiod -b python-bindings-3

Configure and build:

cd libgpiod
./autogen.sh
./configure --enable-bindings-python
make

Create yourself a venv so you can install Python packages:

python3 -m venv ~/libgpiod_test_env
source ~/libgpiod_test_env/bin/activate

Now you can attempt to install the sdist:

pip install bindings/python/dist/libgpiod-2.0.1.tar.gz

Testing

This package should, in theory, work on any platform with Python >= 3.10.0 and GPIO character device support.

To see if you have any supported devices:

ls /dev/gpiochip*

The following test script should toggle line 15 1000 times and report how long it took-

⚠️ Make sure you don't try to import gpiod or run the below from the libgpiod/bindings/python directory.

import gpiod
import time

CONSUMER = "Benchmark"
LINE = 15

chip = gpiod.Chip("/dev/gpiochip4")

lines = chip.request_lines(consumer=CONSUMER, config={
    LINE: gpiod.LineSettings(
        direction=gpiod.line.Direction.OUTPUT,
        output_value=gpiod.line.Value.INACTIVE
    ) 
})

t_start = time.time()

n = 1000

for x in range(n):
    lines.set_value(LINE, gpiod.line.Value.ACTIVE)
    lines.set_value(LINE, gpiod.line.Value.INACTIVE)

t_end = time.time()

print(f"Toggling {n} times took: {(t_end - t_start) * 1000:0.4f}ms")

[Gadgetoid]

Replaced