Cover case when no device has been found.

Initialization of the device must be done after device is detached from
kernel, otherwise exception will be thrown about device is busy message.

README.rst

@@ -2,6 +2,9 @@
 Linak-ctrl
 ==========
 
+.. image:: https://badge.fury.io/py/linak-ctrl.svg
+   :target: https://badge.fury.io/py/linak-ctrl
+
 Simple python script to control Linak powered desks and USB2LIN06 cable.
 
 
@@ -14,6 +17,31 @@ Requirements
 * `pyusb`_
 
 
+Installation
+============
+
+There are couple of different ways for installing ``linak-ctrl``. One of the
+preferred ways is to use virtualenv and pip:
+
+.. code:: shell-session
+
+   $ git clone https://github.com/gryf/linak-ctrl
+   $ cd linak-ctrl
+   linak-ctrl $ python -m venv linak
+   (linak) linak-ctrl $ pip install .
+   (linak) linak-ctrl $ linak-ctrl status
+   Position: 767, height: 78.80cm, moving: False
+
+Or, you can install it system-wide:
+
+.. code:: shell-session
+
+   $ sudo pip install linak-ctrl
+
+And finally, you could also install dependences from your system repositories,
+and use script directly, by placing it somewhere in your ``$PATH``.
+
+
 Usage
 =====
 

linak_ctrl.py

@@ -111,6 +111,14 @@ class LinakDevice:
     def __init__(self):
         self._dev = usb.core.find(idVendor=LinakDevice.VEND,
                                   idProduct=LinakDevice.PROD)
+        if not self._dev:
+            raise ValueError(f'Device {LinakDevice.VEND}:'
+                             f'{LinakDevice.PROD:04d} '
+                             f'not found!')
+
+        # detach kernel driver, if attached
+        if self._dev.is_kernel_driver_active(0):
+            self._dev.detach_kernel_driver(0)
 
         # init device
         buf = [0 for _ in range(BUF_LEN)]
@@ -123,25 +131,18 @@ class LinakDevice:
         # hold a little bit, to make it effect.
         time.sleep(0.5)
 
-        # detach kernel driver, if attached
-        if self._dev.is_kernel_driver_active(0):
-            self._dev.detach_kernel_driver(0)
-
     def get_position(self, args):
-        if args.loop:
-            try:
-                while True:
-                    report = self._get_report()
-                    LOG.warning('Position: %s, height: %.2fcm, moving: %s',
-                                report.position, report.position_in_cm,
-                                report.moving)
-                    time.sleep(0.2)
-            except KeyboardInterrupt:
-                return
-        else:
-            report = self._get_report()
-            LOG.warning('Position: %s, height: %.2fcm, moving: %s',
-                        report.position, report.position_in_cm, report.moving)
+        try:
+            while True:
+                report = self._get_report()
+                LOG.warning('Position: %s, height: %.2fcm, moving: %s',
+                            report.position, report.position_in_cm,
+                            report.moving)
+                if not args.loop:
+                    break
+                time.sleep(0.2)
+        except KeyboardInterrupt:
+            return
 
     def move(self, args):
         retry_count = 3
@@ -191,7 +192,11 @@ class LinakDevice:
 
 
 def main():
-    device = LinakDevice()
+    try:
+        device = LinakDevice()
+    except ValueError as ex:
+        sys.stderr.write(ex.args[0] + '\n')
+        sys.exit(1)
 
     parser = argparse.ArgumentParser('An utility to interact with USB2LIN06 '
                                      'device.')

requirements.txt

@@ -0,0 +1,2 @@
+pbr
+pyusb>=1.1.1

setup.cfg

@@ -0,0 +1,34 @@
+[metadata]
+name = linak-ctrl
+summary = Control Linak powered desks using USB2LIN06 cable. 
+description-file = README.rst
+author = Roman Dobosz
+author-email = gryf73@gmail.com
+home-page = https://gihtub.com/gryf/linak-ctrl
+license = BSD
+classifier =
+    Development Status :: 5 - Production/Stable
+    Environment :: Console
+    Intended Audience :: End Users/Desktop
+    License :: OSI Approved :: BSD License
+    Operating System :: POSIX :: Linux
+    Programming Language :: Python
+    Programming Language :: Python :: 3
+    Programming Language :: Python :: 3.7
+    Programming Language :: Python :: 3.8
+    Programming Language :: Python :: 3.9
+    Topic :: System :: Networking
+
+[install]
+record = install.log
+
+[options.entry_points]
+console_scripts =
+    linak-ctrl= linak_ctrl:main
+
+[options]
+install_requires =
+    pyusb
+
+[bdist_wheel]
+universal = 1

setup.py

@@ -0,0 +1,4 @@
+import setuptools
+
+
+setuptools.setup(setup_requires=['pbr>=2.0.0'], pbr=True)