ENV{DEVNAME} in remove rule?

ENV{DEVNAME} in remove rule?

[Richard Michael]

Hello,

I'm learning my way around udev, and have written these rules to add a
device:

KERNEL="sd*[!0-9]", ENV{ID_SERIAL}="", IMPORT{program}="/lib/udev/usb_id -x"
KERNEL="sd*[!0-9]", ENV{ID_TYPE}="?*", IMPORT{program}="/lib/udev/path_id %p"
KERNEL="sd*[!0-9]", ENV{ID_PATH}="*usb-0:6:1.0*", NAME="storage/raid-$env{ID_BUS}-%M-%m"

I want to run a command when it is removed, so I've written these rules:
(The first rule is a catch-all where I do "set >> /tmp/debug" to see
what's available in the environment..)

SUBSYSTEM="*", RUN+="/root/udev-catch-remove"
ENV{DEVNAME}="/dev/storage/raid-*", RUN+="/root/raid_management"

When the device is disconnected, "udevmonitor --env" shows me:
(DEVNAME appears just as I hoped..)

UDEV  [1183481937.246643] remove   /block/sdc (block)
UDEV_LOG=7
ACTION=remove
DEVPATH=/block/sdc
SUBSYSTEM=block
SEQNUM\x1266
MINOR2
MAJOR=8
PHYSDEVPATH=/devices/pci0000:00/0000:00:0b.1/usb2/2-6/2-6:1.0/host15/target15:0:0/15:0:0:0
PHYSDEVBUS=scsi
PHYSDEVDRIVER=sd
UDEVD_EVENT=1
ID_VENDOR=Maxtor_6
ID_MODELà40L0
ID_REVISION\b11
ID_SERIAL=Maxtor_6_E040L0
ID_TYPE=disk
ID_BUS=usb
ID_PATH=pci-0000:00:0b.1-usb-0:6:1.0-scsi-0:0:0:0
DEVLINKS=/dev/disk/by-id/usb-Maxtor_6_E040L0 /dev/disk/by-path/pci-0000:00:0b.1-usb-0:6:1.0-scsi-0:0:0:0
DEVNAME=/dev/storage/raid-usb-8-32


But, my command /root/raid_management is never run, as if udev isn't
matching ENV{DEVNAME}.

What have I misunderstood?

This is on Fedora 7 machine, using (slightly old) udev 106.
("rpm -q udev" =  udev-106-4.fc7)


Thanks,
Richard

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Re: ENV{DEVNAME} in remove rule?

[Andrey Borzenkov]

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On Tuesday 03 July 2007, Richard Michael wrote:
>
> But, my command /root/raid_management is never run, as if udev isn't
> matching ENV{DEVNAME}.
>
> What have I misunderstood?
>

DEVNAME is set by udev before calling RUN programs. It is not available when 
rules are being processed. 

In general I am not sure it is wise to match on DEVNAME It can be changed at 
any time by installing different rule(s). Better to match on device 
properties.

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Re: ENV{DEVNAME} in remove rule?

[Richard Michael]

> DEVNAME is set by udev before calling RUN programs. It is not available when 
> rules are being processed. 

Where are these details documented?  I've been writing lots of test
rules to try and figure this out, but I'd prefer to just read something.

> In general I am not sure it is wise to match on DEVNAME It can be changed at 
> any time by installing different rule(s). Better to match on device 
> properties.

I'd really prefer to match PHYSDEVPATH, because what I actually care
about is identifying the USB socket which the device is attached
(especially for the "add" rule.. the "remove" just uses the device name
as I set it when it was added).  However, PHYSDEVPATH has been
deprecated.

I want to create block devices (not symlinks) for the specific ports of
a USB (or firewire) controller, and take actions depending on which
socket of the controller has been used.

Thanks,
Richard

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Re: ENV{DEVNAME} in remove rule?

[Andrey Borzenkov]

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On Tuesday 03 July 2007, Richard Michael wrote:
> > DEVNAME is set by udev before calling RUN programs. It is not available
> > when rules are being processed.
>
> Where are these details documented? 

source code?

> I've been writing lots of test 
> rules to try and figure this out, but I'd prefer to just read something.
>

patches to manual pages are welcome :)

>
> I want to create block devices (not symlinks) for the specific ports of
> a USB (or firewire) controller, and take actions depending on which
> socket of the controller has been used.
>

What's wrong with using ID_PATH? It also has advantage of being more stable 
than PHYSDEVPATH (which includes volatile details like running SCSI host 
number).

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Re: ENV{DEVNAME} in remove rule?

[Richard Michael]

On Tue, Jul 03, 2007 at 10:06:08PM +0400, Andrey Borzenkov wrote:
> On Tuesday 03 July 2007, Richard Michael wrote:
> > > DEVNAME is set by udev before calling RUN programs. It is not available
> > > when rules are being processed.
> >
> > Where are these details documented? 
> 
> source code?

I thought so.  I think udev is great, it just needs slightly more helpful
documentation to make is really user accessible.  There are quite a few
"things to know" (such as the default PATH, which took awhile to
realize I was overlooking..).

> > I've been writing lots of test 
> > rules to try and figure this out, but I'd prefer to just read something.
> >
> 
> patches to manual pages are welcome :)

I was thinking about changes to the How To Write UDev Rules document..
 
> What's wrong with using ID_PATH? It also has advantage of being more stable 
> than PHYSDEVPATH (which includes volatile details like running SCSI host 
> number).

Yes, I noticed the target number changes even when the hardware remains
identical.

I thought I had a problem running path_id/usb_id to set those environment
variables (I don't remember which one sets them..), because the sysfs
entry was already gone.  I think I misunderstood, maybe the variables
are set from when the device was created? .. I'll look into again.  I'm
probably just confused, it's been a bit of mess building some
understanding.. :)

Thanks,
Richard

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Re: ENV{DEVNAME} in remove rule?

[Andrey Borzenkov]

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On Tuesday 03 July 2007, Richard Michael wrote:
> I thought I had a problem running path_id/usb_id to set those environment
> variables (I don't remember which one sets them..), because the sysfs
> entry was already gone.  I think I misunderstood, maybe the variables
> are set from when the device was created? 

Yes. You have to import them (unless already done) on "add" event; those 
values are stored in udev database and added to environment *before* rules 
are being processed on "remove" event. At least that is the theory :)

You also can explicitly assign any environment variable on "add" and it should 
be available as well on "remove". This allows you to mark any specific device 
if you like.

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