On Thu, Aug 21, 2008 at 03:37, Aras Vaichas <arasv@xxxxxxxxxxxxxx> wrote:
> Hi, I'm looking to unload a userspace driver when a particular device is
> removed.
>
> My load rule is this:
>
> ACTION=="add",SUBSYSTEM=="usb_endpoint",ATTR{device/manufacturer}=="Crystalfontz",
> RUN+="/usr/bin/sv up lcdd"
>
> Now the problem was that when I disconnect the device there is no longer
> a "device/manufacturer" file, so I added an environment variable
> LCDD_DEVICE to the rule:
>
> ACTION=="add",SUBSYSTEM=="usb_endpoint",ATTR{device/manufacturer}=="Crystalfontz",
> ENV{LCDD_DEVICE}="%k", RUN+="/usr/bin/sv up lcdd"
Why do you match against the endpoint? These devices do not do anything.
You should also never use the "device" link, it's deprecated and udev
should print a warning to the logs.
> I had hoped to be able to match this LCDD_DEVICE variable when the
> kernel name appeared in the remove event. So I tried:
>
> ACTION=="remove", ENV{LCDD_DEVICE}=="%k", RUN+="... remove the driver ..."
>
> But this rule never triggered.
>
> I put in a debug line, and disconnected the device:
>
> ACTION=="remove", RUN+="/bin/sh -c 'logger B %k = $env{LCDD_DEVICE}'"
>
> Jan 1 00:41:21 user.notice root: B usbdev1.23_ep81 =
> Jan 1 00:41:21 user.notice root: B usbdev1.23_ep02 =
> Jan 1 00:41:21 user.notice root: B usbdev1.23_ep00 = usbdev1.23_ep00
> <--- !!!
> Jan 1 00:41:21 user.notice root: B ttyUSB1 =
> Jan 1 00:41:21 user.notice root: B ttyUSB1 =
> Jan 1 00:41:21 user.notice root: B 1-1:1.0 =
> Jan 1 00:41:21 user.notice root: B 1-1 =
>
> So there is a situation where %k was equal to LCDD_DEVICE, but
> regardless the rule didn't trigger. Did I get the syntax wrong?
>
> Also, it appears that the scope of the environment variable LCDD_DEVICE
> only occurs when the actual device has caused the uevent. OK.
>
> So should I make my remove rule like this?
>
> ACTION=="remove", ENV{LCDD_DEVICE}!="", RUN+="... remove the driver ..."
By matching on the endpoint, you get several events which will all
trigger your script. Try using the USB-device only, by adding:
ENV{DEVTYPE}=="usb_device"
Try setting:
ENV{REMOVE_CMD}="/bin/something"
with the "add" rule, it should be called by udev itself on "remove".
Kay
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