Need help with access to USB serial ports [Was: Classic confinement request: zworkbench]

snapd
1

This is IDE for programing PLC, need access for serial ports.

2

are these actual serial ports, not usb-serial (for which you would be able to use the raw-usb interface like i.e. the rpiboot snap) ?

3

You could also try using the new serial-hotplug in the edge channel of the core snap. See Hotplug support for more details

4

Hello! I am use usb-serial (rs485) converter. On host machine add user to dialout group. Then make “cat /dev/ttyUSB0” - works.

Then
Attemp 1:
Add to snapcraft.yaml:

plugs:
serial-port:
interface: serial-port
apps:
zworkbench:
plugs:
- serial-port

Result: Not work

Attemp 2:
Add to snapcraft.yaml:

plugs:
  serial-port:
    interface: serial-port
    **path: /dev/tty[A-U]***
apps:
  zworkbench:
    plugs:
      - serial-port

Result: Not work

Attemp 3:
Add to snapcraft.yaml:

slots:
    ttyUSB0:
      interface: serial-port
      path: /dev/ttyUSB0

Result: Not work (required manual confirm, as classic)

Attemp 4:
run snap run --shell zworbench, run in snap “cat /dev/ttyUSB0”
Result: Not work (Permission denied)

Attemp 5:
Find project “tio”, experiment with my usb-rs485 conventer. WORK! Find snapcraft.yaml (https://github.com/tio/tio.snapcraft/blob/master/snap/snapcraft.yaml) for tio, it is use “classic”…
Add classic for zworkbench… Result, need confirm =) Add topic in forum… wait =)))
Result: Not work (required manual confirm)

5

Also with strict mode I use in snapcraft.yaml, i think if use classic is will be simple for this project:

<… cut other more line in snapcraft.yaml …>

plugs:
kde-frameworks-5-plug:
interface: content
content: kde-frameworks-5-all
default-provider: kde-frameworks-5
target: kf5
serial-port:
interface: serial-port
path: /dev/tty[A-U]*

apps:
zworkbench:
command: zworkbench
environment:
LD_LIBRARY_PATH: “$LD_LIBRARY_PATH:/$SNAP/usr/lib/$SNAPCRAFT_ARCH_TRIPLET/pulseaudio”
desktop: usr/share/applications/zworkbench.desktop
plugs:
- network
- network-bind
- network-manager
- network-observe
- home
- opengl
- pulseaudio
- mount-observe
- optical-drive
- camera
- removable-media
- screen-inhibit-control
- x11
- unity7
- desktop
- desktop-legacy
- wayland
- gsettings
- kde-frameworks-5-plug
- serial-port
slots:
- mpris

6

Now test add raw-usb for strict. Result: Not works, also can not open port in snap app. In host all works =(

7

Enable hotplug, restart snapd, reconnect-connect usb-rs485. Result: not work =(

8

did you actually verify that hotplug is enabled and working first ?

sudo snap refresh core --edge
sudo snap set core experimental.hotplug=true

now plugging in a serial USB device:

$ dmesg | tail -3
[   98.838110] usb 4-1: Manufacturer: Prolific Technology Inc.
[   98.840462] pl2303 4-1:1.0: pl2303 converter detected
[   98.862564] usb 4-1: pl2303 converter now attached to ttyUSB0

and verifying that snapd created a hotplug interface:

$ snap interface serial-port
name:    serial-port
summary: allows accessing a specific serial port
slots:
  - core:pl2303serialport (allows accessing a specific serial port)
$ snap connections system|grep serial
serial-port              -                      :pl2303serialport         -

now your app should be able to connect to it via a serial-port plug that uses /dev/ttyUSB0 as path …

9

Hello! coverter connected, file “/dev/ttyUSB0” exist. Enabled serial-port interface, but not connected to serial-port snap. =(
Result screenshot:

image
image1006×360 70.1 KB

P.S. Our users can not program PLC device without access to serial port… You can enable classic for zworkbench app? I am update info in snap info site of the zworkbench, add screenshot, add email, add site, add icon. =)

10

did you run:

sudo snap refresh core --edge
sudo snap set core experimental.hotplug=true

it does not look like hotplug is actually enabled at all … perhaps @pstolowski could also give us some more hints here.

note that snaps where an interface exists to achieve their functionality are per store-rule not allowed to get classic confinement … we need to get your serial interface to work.

11

If the only reason for classic is access to /dev/ttyUSB0, then the request is denied since that can be handled via raw-usb or the new hotplug feature. While this seems to be understood by everyone in this discussion, I wanted other @reviewers to understand nothing more needs to be done with this request. Please proceed to work with others to enable your snap to work in strict mode. Thanks.

12

To that end, I renamed the topic and moved it to the appropriate category.

13

Hello! Sorry for delay!

Why project tio use classic??? Tio use only serial-ports. Please denied classic for tio project =)))

Result:
experimental.hotplug=true <- not work
serial-port <- not work
raw-usb <- not work

Work only if install with --devmode parameter =(((

My snap:
<… cut other build lines …>
plugs:
kde-frameworks-5-plug:
interface: content
content: kde-frameworks-5-all
default-provider: kde-frameworks-5
target: kf5
serial-port:
interface: serial-port

apps:
zworkbench:
command: zworkbench
environment:
LD_LIBRARY_PATH: “$LD_LIBRARY_PATH:/$SNAP/usr/lib/$SNAPCRAFT_ARCH_TRIPLET/pulseaudio”
desktop: usr/share/applications/zworkbench.desktop
plugs:
- network
- network-bind
- network-manager
- network-observe
- home
- opengl
- pulseaudio
- mount-observe
- optical-drive
- camera
- removable-media
- screen-inhibit-control
- x11
- unity7
- desktop
- desktop-legacy
- wayland
- gsettings
- kde-frameworks-5-plug
- serial-port
- raw-usb
slots:
- mpris