How do I disable brltty?

English Hardware
1

I have a microcontroller system to be connected via USB, which sets up a /dev/ttyUSB0. I recently noticed that the Braille driver (brltty) tries to grab the device and fails, since it is not a braille device. This did not happen earlier (can’t tell when).

  502.380633] usbcore: registered new interface driver usbserial_generic
  502.380641] usbserial: USB Serial support registered for generic
  502.382066] usbcore: registered new interface driver cp210x
  502.382072] usbserial: USB Serial support registered for cp210x
  502.382084] cp210x 1-11:1.0: cp210x converter detected
  502.383648] usb 1-11: cp210x converter now attached to ttyUSB0
  502.422511] usb 1-11: usbfs: interface 0 claimed by cp210x while 'brltty' sets config #1
  502.422924] cp210x ttyUSB0: cp210x converter now disconnected from ttyUSB0
  502.422935] cp210x 1-11:1.0: device disconnected

When I uninstall the brltty packages, it works, but they are reinstalled on every zypper dup. It seems more reasonable to disable the service, but I could not get systemctl to do that.

# systemctl stop brltty@-dev-bus-usb-001-004.service
Failed to stop brltty@-dev-bus-usb-001-004.service: Operation refused, unit brltty@-dev-bus-usb-001-004.service may be requested by dependency only (it is configured to refuse manual start/stop).
See system logs and 'systemctl status brltty@-dev-bus-usb-001-004.service' for details.

Suggestions welcome.

2

Lock those packages?
See

man zyppr

under “Package Locks Management”.

3

Please check the output of “rpm --query --whatrequires brltty”.

  • On this Leap 15.0 system, there are no packages which “require” require the package “brltty” – which is why it ain’t installed here …
  • It may be that, a YaST “pattern” which is forcing the installation of “brltty” – but, on searching Leap 15.0 I can’t find a pattern which could be causing this issue …
4

It’s about Tumbleweed, not Leap.


# rpm --query --whatrequires brltty
xbrlapi-5.6-2.6.x86_64
brltty-lang-5.6-2.6.noarch
brltty-driver-xwindow-5.6-2.6.x86_64
brltty-driver-speech-dispatcher-5.6-2.6.x86_64
brltty-driver-brlapi-5.6-2.6.x86_64
brltty-driver-at-spi2-5.6-2.6.x86_64

I know that I can prevent reinstallations by blocking, but I’d prefer not to keep records of stuff that I blocked over time. My understanding is that I should be able to turn off services that I don’t need.

Typically, I’d disable services with systemctl, but in this case I can’t find which is the component that originally requests it. The brltty is “static” in systemctl is-enabled.

Googling reveals that brltty has been interfering with ttyUSB for more than 10 years…

5

Hi
You ‘mask’ the static service… (not running here)


systemctl status brltty.path 

● brltty.path - Default BRLTTY Instance
   Loaded: loaded (/usr/lib/systemd/system/brltty.path; disabled; vendor preset: disabled)
   Active: inactive (dead)

systemctl mask brltty.path 

Created symlink /etc/systemd/system/brltty.path → /dev/null.
6

@mizapf:

Looking at the “Requires” list, the culprit may well be ‘xbrlapi’ – please check “whatrequires” the X system Braille API …

7

I found a way to disable it:

ln -s /dev/null /etc/udev/rules.d/69-brltty.rules

There is a file with the same name in /usr/lib/udev/rules.d/. This seems to launch the brltty. I wonder why this issue appeared again (seemed to be going back for 10 years); maybe the rules have a bug. I noticed a comment in /etc/brltty.conf that says that a braille display behind a serial-to-USB adapter will not work via the “usb:” path but the actual virtual interface (ttyUSB0) must be specified. Maybe some brltty dev felt really smart and lets it grab the first ttyUSBx that shows up.

8

It may be better to simply invoke “rpm --query --whatprovides /etc/udev/rules.d/69-brltty.rules /usr/lib/udev/rules.d/69-brltty.rules” …

  • If they ain’t being provided by any package, simply remove those two files …