Re: Generic udev rule for PTP camera

[Andrey Borzenkov <arvidjaar@mail.ru>]

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On Thursday 16 November 2006 16:27, Frederic Peters wrote:
> Hello,
>
> For a long time, since we totally switched from hotplug to udev, we
> have been unable in Debian to provide fallback support for unknown
> PTP cameras.
>
> Hotplugging any known camera works perfectly but this require
> attentive maintenance of matching USB id and always lags behind
> constructors.
>
> PTP camera devices define an interface which I thought could be
> matched by the following rule:
>
> SYSFS{bInterfaceClass}="06", SYSFS{bInterfaceSubClass}="01", \
>   SYSFS{bInterfaceProtocol}="01", MODE="0660", GROUP="plugdev"
>
> Unfortunately this doesn't work. 

I do not have PTP camera to test, but both /dev/bus/usb/... nodes I can create 
here point to sysfs device *above* interface. Which effectively means, that 
when you rule matches, there is no device to create; and when device is 
created your rule does not match (because those attributes do not exist on 
this level)

> Then Marcus Meissner from libgphoto2 
> suggested to use ENV{INTERFACE}="6/1/1" as matcher but I can't get it
> to work and Marco d'Itri (Debian udev maintainer) believe this not to
> be the correct solution anyway.
>

I guess it fails for the same reason.

> Since Marco doesn't have much time for the moment he suggested I asked
> the question here, so here it is: what would be the rule to use to set
> mode/group on /dev/bus/usb/... device when detecting this device by
> bInterface{Class/SubClass/Protocol} ?
>
> For the record, I copied below the output of udevmonitor --env when
> plugging in a camera.
>

[...]
>
> UEVENT[1163683152.647503]
> add@/devices/pci0000:00/0000:00:1d.7/usb1/1-2/1-2:1.0 ACTION­d
> DEVPATH=/devices/pci0000:00/0000:00:1d.7/usb1/1-2/1-2:1.0
> SUBSYSTEM=usb
> SEQNUM\x1710
> PHYSDEVBUS=usb
> DEVICE=/proc/bus/usb/001/004
> PRODUCTJ9/30fd/2
> TYPE=0/0/0
> INTERFACE=6/1/1
> MODALIAS=usb:v04A9p30FDd0002dc00dsc00dp00ic06isc01ip01
>

This is your interface

[...]
>
> UEVENT[1163683152.647657] add@/class/usb_device/usbdev1.4
> ACTION­d
> DEVPATH=/class/usb_device/usbdev1.4
> SUBSYSTEM=usb_device
> SEQNUM\x1714
> PHYSDEVPATH=/devices/pci0000:00/0000:00:1d.7/usb1/1-2
> PHYSDEVBUS=usb
> PHYSDEVDRIVER=usb
> MAJOR\x189
> MINOR=3
>

And here is where your /dev/bus/usb/... node is created.


Something like this /could/ work:

SYSFS{bInterfaceClass}="06", SYSFS{bInterfaceSubClass}="01", \
  SYSFS{bInterfaceProtocol}="01", RUN+="sh -c 'echo ${DEVPATH%/*} 
>> /tmp/perms'"

SUBSYSTEM=udb_device, PROGRAM="grep -q $DEVPATH /tmp/perms", GROUP="plugdev" 
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