/proc/bus/usb is obsolete

[alexander@…]

While the instructions at the libusb page still work with linux-2.6.14, they describe the obsolete setup. The /proc/bus/usb mount should go away, and libusb should be patched to take advantage of real raw usb device nodes. Use this raw message as a patch for libusb:

​http://marc.theaimsgroup.com/?l=linux-hotplug-devel&m=112447064921992&q=raw

The udev rule that is equivalent to the current setup WRT permissions is:

SUBSYSTEM=="usb_device", PROGRAM="/bin/sh -c 'X=%k X=$${X#usbdev} B=$${X%%%%.*} D=$${X#*.}; echo bus/usb/$$B/$$D'", SYMLINK+="%c", GROUP="usb"

(that is one long line)

Fine-tunuing of permissions is possible by creating extra rules, matching on something like this:

SUBSYSTEM=="usb_device", SYSFS{idVendor}=="05d8", SYSFS{idProduct}=="4002", GROUP:="scanner"

[alexander@…]

LFS should integrate the udev rule above.

The patch is no longer needed with libusb-0.1.12. This version of libusb first tries /dev/bus/usb (where udev creates real device nodes with the above rule) and then falls back to /proc/bus/usb (should not happen with linux >= 2.6.14 with proper udev rules, because /dev/bus/usb is always available). Thus, if all applications requiring raw access to USB devices used libusb, one could remove the /proc/bus/usb mount. Unfortunately, VMware and other proprietary apps beyond BLFS may still need this obsolete mount point because they don't use libusb.

/dev/bus/usb and /proc/bus/usb don't conflict. It's just that udev can't be used to set /proc/bus/usb permissions reliably.

[archaic@…]

After a very informative conversation with Alexander on this subject it looks like a compromise may be reachable that serves the purpose of base-system configuration, and educational value through BLFS extending that configuration. Details forthcoming on lfs-dev.

[bdubbs@…]

I've made some changes to the config section of libusb.

​http://www.linuxfromscratch.org/blfs/view/cvs/general/libusb.html

Leaving the ticket open for now waiting for critiques.

[alexander@…]

There is a conflict between the LFS and BLFS rules. LFS already names USB devices (basically the first rule but with NAME=... instead of SYMLINK), thus, the BLFS rule should be:

SUBSYSTEM=="usb_device", GROUP="usb"

But, that's insecure. The "usb" group must die (it was a hack invented by me in order to avoid the dependency of SANE on Hotplug). Rules of the second kind (matching on vendor and product IDs are already a part of SANE package, but are not installed in BLFS (that's a bug). For libgphoto2, there is a Debian-specific patch that adds a generator for such rules.

As for the /proc/bus/usb mount point, it would be nice to list an example of an application that does require it: VMware.

[bdubbs@…]

Added comment about /proc/bus/usb in "About Devices" page.

Committed revision 6099.