[BRLTTY] udev with systemd

[Mike Gorse]

On Fri, 8 Jan 2016, Mike Gorse wrote:

> On Fri, 8 Jan 2016, Mike Gorse wrote:
>
>>> Please test the latest commit to verify that it's correct.
>> 
>> Tested. Yes, that works.
>> 
>>> Is there something we can do on remove in order to stop the service?
>> 
>> I asked a colleague who is more familiar with systemd than I am, and he 
>> pointed me to this link:
>> 
>> http://unix.stackexchange.com/questions/63232/what-is-the-correct-way-to-write-a-udev-rule-to-stop-a-service-under-systemd
>> 
>> However, when I run
>> systemctl list-units --all --full |grep .device
>> I get this for the Brailliant:
>> dev-brltty-auto\x2dusb:25000072.device loaded    active   plugged 
>> Brailliant_40
>> dev-bus-usb-003-039.device loaded    active   plugged   Brailliant_40
>> 
>> So it appears that I need a fixed device name that systemd could bind to 
>> for any Braille display. I've just tested having the udev rules file create 
>> a symlink called "braille" and have systemd bind to it, and now it unloades 
>> when I remove the display. Patch attached.
>
> On second thought, that patch isn't right--it makes systemd require the 
> device in order to load brltty, which will break for a serial or a bluetooth 
> device.

The After= line doesn't appear to be necessary; if I remove it, then 
systemd still unloads brltty when I disconnect my device, but it is still 
possible to start brltty manually via systemd without a USB device 
connected. Revised patch attached.
-------------- next part --------------
diff --git a/Autostart/Systemd/brltty.service.in b/Autostart/Systemd/brltty.service.in
index 87f26ca..72188fa 100644
--- a/Autostart/Systemd/brltty.service.in
+++ b/Autostart/Systemd/brltty.service.in
@@ -6,6 +6,7 @@ Documentation=http://brltty.com/
 
 DefaultDependencies=no
 Before=sysinit.target
+BindsTo=dev-braille.device
 
 RequiresMountsFor=@UPDATABLE_DIRECTORY@
 
diff --git a/Autostart/Udev/udev.rules b/Autostart/Udev/udev.rules
index 4d9926f..0259ab5 100644
--- a/Autostart/Udev/udev.rules
+++ b/Autostart/Udev/udev.rules
@@ -447,6 +447,7 @@ RUN+="/bin/brltty -E -P$env{BRLTTY_PID_FILE}"
 GOTO="brltty_end"
 
 LABEL="brltty_add_systemd"
+SYMLINK+="braille"
 TAG+="systemd", ENV{SYSTEMD_WANTS}+="brltty.service"
 GOTO="brltty_end"