Re: udev remove ATTR(S) not working

[Andrey Borzenkov <arvidjaar@mail.ru>]

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On Saturday 09 June 2007, Farkas Levente wrote:
> Andrey Borzenkov wrote:
> >> On 6/7/07, Farkas Levente <lfarkas@bppiac.hu> wrote:
> >>> hi,
> >>> how can i write a RUN udev rules for remove event? i want to recognize
> >>> my usd pendrive's add and remove. the add is simple since i can use
> >>> rather specific rules like:
> >>> ---------------------------------------
> >>> ACTION=="add", SUBSYSTEM=="block", ATTR{size}=="2880",
> >>> ATTRS{serial}=="07530736300A", ATTRS{product}=="USB DISK Pro",
> >>> RUN+="/xxx" ---------------------------------------
> >>> but the remove rule is much complicated, since (at least it seems for
> >>> me) udev don't send ATTR(S) in this case and don't know about anymore
> >>> the removed device parameters.
> >
> > If you absolutely need them on remove (could you explain why? What
> > exactly are you trying to do?), set environment vars on add and use
> > (match) them on remove.
>
> how can i do so?

just like you did. ENV{foo}="bar" on add.

> eg i create a new link SYMLINK+="lfarkas" in the add action
> and in this case in remove actions env contains
> DEVLINKS='/dev/lfarkas /dev/...'
> BUT a rule like this:
> ACTION=="remove", SUBSYSTEM=="block", ENV{DEVLINKS}=="/dev/lfarkas*"
> never match, 

Because DEVLINKS does not come from persistent environment. Check with 
udevinfo --query=env.

> so how can i match for DEVLINKS?

well, again, are you sure you really need it? What do you try to do?

> or what other methods exists for properly identify a removed device?

Device is identified by DEVPATH. If you mean - you need to fetch special 
device attributes that you had set during device add event - you can either 
store them as environment variable or implement your own on-disk persistent 
store.

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