[BRLTTY] The brltty service gets in the way of other serial port applications

[Dave Mielke]

[quoted lines by John on 2023/12/15 at 15:23 +0000]

>As per advice, I disabled both services, but this unfortunately did not restore normality. In fact, the service was still being loaded as could be evidenced by running the 'ps -ef' command to show a list of running processes.

Disabling the brltty service doesn't prevent it from being automatically started by a USB udev rule. If you really don't want a Systemd unit to start then you need to systemctl mask it.

>I should point out that Arduino is not the only area of electronics that I work with, that also requires access to serial ports.

I hope it's okay for me to point out that Arduino and friends are just as much to blame as brltty is. Brltty's problem is that some braille device manufacturers don't bother customizing their USB vendor and product IDs. Yes, they should do it. Also, however, so should Arduino and friends be doing exactly the same thing. There'll always be such conflicts as long as whomever doesn't stop using generic vendor/product IDs.

>Whereas I appreciate the necessity of having such software for those who
>need Braille, I don't understand why it was installed automatically as a
>mainstream service as part of an OS update? 

So that blind people who use braille can actually read their screens. Try closing your eyes, promising not to peak even once, and interact with your system. It won't matter how well your monitor is working - you won't be able to do it. Are you suggesting that blind people should only ever install a Linux system when they have a sighted assistant?

>I would expect such a program to be installed on an as-needs basis?

Can you suggest a way to design it that way? Since you expect it to be that way, you must have some idea regarding how to do it that way. A braille user would be unable to make such a choice without first being able to read his/her screen, which means, yes, that his/her braille deivce must already be working. Let's call it one of those "catch 22" situations.

>Secondly, disabling the service ought to have been sufficient to prevent
>the software from disrupting the operation of the system, but it wasn't.

That's how Systemd units work. An equivalent, for example, would be how a service unit is still automatically started if its corresponding socket unit is activated.

>It had to be completely removed. Is this a bug? If so, where do I report
>it? I see the 'issues' function on the Github repository is not enabled.

No, it's not a bug. But, to answer your question, this inndeed is where to report bugs.

>Thirdly, can the software be configured to ignore certain ports?

Brltty tries as hard as it can to only consider actual braille devices. As mentioned above, however, we can't help it when some manufacturers choose to use generic IDs and we also don't wish to exercise any control or influence over which braille device any given user chooses to use.

Again, however, I'll ask why is it that Arduino feels that it's okay for it to be using generic IDs. Does something make Arduino more important than a braille device? Of course not! It's all a matter of personal perspective, and, to me, that makes it wrong to favour one over the other.

>Finally, if a program or update is likely to disrupt what might
>generally be considered 'normal' operation of the system (I "generally"
>because I accept that for users of Braille, having brltty installed is
>their 'normal'), shouldn't the software at least warn the user of this
>and request confirmation before installing itself? 

Again, how would you design it that way? How can a braille user read such a warning and/or respond to such a confirmation before his/her braille device is working?

Now that I've griped a bit at you, I'll tell you the simplest way to deal with this issue. First, do:

   brltty --version

If it's earlier than 6.5 then your distribution is too old. As of brltty-6.5, we split our USB rules into two - generic and customized. So, all you really need to do is to ensure that you're at least at brltty-6.5 and then to uninstall the generic USB rules package.

>I am curious as to how and why it suddenly appeared on my system.

Probably due to an upgrade to a newer brltty release which introduced support for a braille device that's using the same generic IDs as you are.

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