libgphoto2 calls hotplug script with wrong variables

libgphoto2 calls hotplug script with wrong variables

[Moshe Yudkowsky]

I can fix this myself, but I'm curious to know if anyone else has fixed 
it, if it needs a bug report, or if something is very wrong with the way 
my system works.

My udev directory has a file called "libgphoto2.rules" -- I didn't put 
it there, but I don't know which package did (from the changelog, I 
suspect it was libgphoto2 package using a utility called 
"print-udev-rules").

In any case, when I plug in a USB camera, the file will use manufacturer 
and product code to find RUN+="/etc/hotplug/usb/libgphoto2".

Here's some problems:

(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.

(1b) I also keep reading about HAL, but it isn't installed on my machine 
accoring to dpkg. Should it be? If it is supposed to be, why isn't in 
installed -- which script should have installed it?

(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 uses the environment variable $DEVICE. Now, that's 
interesting, because the udev man page doesn't mention this variable in 
the ENVIRONMENT section of the page at all, and it makes me wonder just 
what variables are available to anything I run as a RUN+= script. Not 
documented?

Problem:

The $DEVICE isn't equivalent to $DEVPATH. For example,

DEVICE is "/proc/bus/usb/002/010"
while
DEVPATH is "/devices/pci0000:00/0000:00:10.1/usb2/2-1/2-1:1.0".

Neither of these is any good when I want to configure the port that's 
been created; what I need is the USB bus device path so I can set group 
permissions. E.g., what I need is

/dev/bus/usb/002/010


No dobut I will find the correct magic combination, but if anyone has 
already solved this problem, please let me know.






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


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Re: libgphoto2 calls hotplug script with wrong variables

[Marco d'Itri]

On Dec 06, Moshe Yudkowsky <msha5_17@bl.com> wrote:

> My udev directory has a file called "libgphoto2.rules" -- I didn't put 
> it there, but I don't know which package did (from the changelog, I 
> suspect it was libgphoto2 package using a utility called 
> "print-udev-rules").
Right. So this is off topic for this mailing list.

> (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.

> (1b) I also keep reading about HAL, but it isn't installed on my machine 
> accoring to dpkg. Should it be? If it is supposed to be, why isn't in 
> installed -- which script should have installed it?
Because libgphoto does not actually use it.

> (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.

-- 
ciao,
Marco


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Re: libgphoto2 calls hotplug script with wrong variables

[Moshe Yudkowsky]

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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Re: libgphoto2 calls hotplug script with wrong variables

[Marco d'Itri]

On Dec 06, Moshe Yudkowsky <msha5_17@bl.com> wrote:

> /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?
/lib/udev/.

> * 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 
There is something on linux-hotplug.sourceforge.net, but it's incomplete
and half-wrong.

-- 
ciao,
Marco


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