Re: libgphoto2 calls hotplug script with wrong variables

[Moshe Yudkowsky <msha5_17@bl.com>]

Thanks to Marco for his replies. I have a couple of additional question, 
and a question that weren't answered.

>>(1a) I keep on reading on this list that /etc/hotplug is supposed to be 
>>deprecated, and yet here's /etc/hotplug that looks pretty official.
> 
> Blame the people who do not want to stop supporting old-style hotplug
> and 2.4 kernels in Debian. Anyway, this is not important.

/etc/hotplug was a convinient place to put scripts associated with 
hotplug events. Is there a "best practice" location for scripts (e.g., 
RUN scripts or PROGRAM scripts) when using udev?

>>(2) The script libgphoto2 doesn't work. The goal of libgphoto2 is to set 
>>the device created by hotplug (later udev) so that anyone in group 
>>$CAMERA can use it, but that doesn't happen, and here's why.
> 
> The script works fine, but updates the /prob/bus/usb/ file.
> You also need an udev rule to set GROUP for the SUBSYSTEM="usb_device"
> event which creates the /dev/bus/usb/ device.

Well, yes, the script modifies /proc -- which is the wrong file. I 
should have been more precise.

Thanks for the tip on SUBSYTEM  -- I was not aware that this was the 
entity that created the /dev/bus/usb device. That makes it very easy to 
create the correct permissions using group with no need for a script.

For the sake of clarity, I always like to include the complete text of 
the fix if possible, so here it is. The solution is to modify the 
"libgphoto2.rules" file. For the Canon S110, to pick an example, the 
entry should read:

SUBSYSTEM="usb_device", SYSFS{idVendor}="04a9", 
SYSFS{idProduct}="3051",  GROUP="camera"

Note that there's no need for any RUN script to set the group.

Here's the unanswered question and a new question:

* Is there a current list of what's available to the environment of 
scripts? I see that libgphoto2 used $DEVICE, and $DEVICE doesn't seem to 
be mentioned on the udev man page as being in the environment spawned by 
RUN.

* Where can I find, other than by asking on this list or reading through 
the code, information about how other subsystems work with udev and what 
they do? /dev/hotplug.log, for example, contains a lot of nice info, and 
I see that one stanza has the information:

> HOTPLUG_TIME='Mon Dec  5 17:36:47 CST 2005'
> PHYSDEVPATH=/devices/pci0000:00/0000:00:10.1/usb2/2-1
> SUBSYSTEM=usb_device
> OLDPWD=/
> DEVPATH=/class/usb_device/usbdev2.20
> MINOR\x147
> ACTION=remove
> UDEV_LOG=7
> MAJOR\x189
> UDEVD_EVENT=1
> DEVNAME=/dev/bus/usb/002/020
> PHYSDEVDRIVER=usb
> PHYSDEVBUS=usb
> SEQNUM\x1033

Is this the best way to find out which SUBSYSTEM to look for -- by 
finding the SUBSYSTEM stanza that has the DEVNAME attached to it? Yes, I 
realize if I were a guru I'd know this stuff, but it's sure not obvious 
to me. Yet.

Regards,
  Moshe


-- 
  Moshe Yudkowsky
  work: http://www.Disaggregate.com
  book: http://www.PebbleAndAvalanche.com


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