2

Let's look at this driver source: http://www.acs.com.hk/download-driver-unified/6258/ACS-Unified-Driver-Lnx-Mac-113-P.zip

After compilation, we seems to end up with two files:

  • libacsccid.so
  • 92-libacsccid1.rules

(there is also Info.plist but it seems to be OS X specific)

On make install first file is being put into /usr/lib/pcsc/drivers/ifd-acsccid.bundle/Contents/Linux/libacsccid.so, and second is supposed to be put in /etc/udev/rules.d/.

The question is... how Linux knows that libacsccid.so file is a driver that has to be used in the specific situation?

This is output of: make --dry-run install:

fail=; \
if (target_option=k; case ${target_option-} in ?) ;; *) echo "am__make_running_with_option: internal error: invalid" "target option '${target_option-}' specified" >&2; exit 1;; esac; has_opt=no; sane_makeflags=$MAKEFLAGS; if { if test -z '0'; then false; elif test -n 'x86_64-pc-linux-gnu'; then true; elif test -n '4.2.1' && test -n '/home/luken/Pobrane/acs-driver/ACS-Unified-Driver-Lnx-Mac-113-P/acsccid-1.1.3'; then true; else false; fi; }; then sane_makeflags=$MFLAGS; else case $MAKEFLAGS in *\\[\ \   ]*) bs=\\; sane_makeflags=`printf '%s\n' "$MAKEFLAGS" | sed "s/$bs$bs[$bs $bs   ]*//g"`;; esac; fi; skip_next=no; strip_trailopt () { flg=`printf '%s\n' "$flg" | sed "s/$1.*$//"`; }; for flg in $sane_makeflags; do test $skip_next = yes && { skip_next=no; continue; }; case $flg in *=*|--*) continue;; -*I) strip_trailopt 'I'; skip_next=yes;; -*I?*) strip_trailopt 'I';; -*O) strip_trailopt 'O'; skip_next=yes;; -*O?*) strip_trailopt 'O';; -*l) strip_trailopt 'l'; skip_next=yes;; -*l?*) strip_trailopt 'l';; -[dEDm]) skip_next=yes;; -[JT]) skip_next=yes;; esac; case $flg in *$target_option*) has_opt=yes; break;; esac; done; test $has_opt = yes); then \
  failcom='fail=yes'; \
else \
  failcom='exit 1'; \
fi; \
dot_seen=no; \
target=`echo install-recursive | sed s/-recursive//`; \
case "install-recursive" in \
  distclean-* | maintainer-clean-*) list='src' ;; \
  *) list='src' ;; \
esac; \
for subdir in $list; do \
  echo "Making $target in $subdir"; \
  if test "$subdir" = "."; then \
    dot_seen=yes; \
    local_target="$target-am"; \
  else \
    local_target="$target"; \
  fi; \
  (CDPATH="${ZSH_VERSION+.}:" && cd $subdir && make  $local_target) \
  || eval $failcom; \
done; \
if test "$dot_seen" = "no"; then \
  make  "$target-am" || exit 1; \
fi; test -z "$fail"
Making install in src
make[1]: Wejście do katalogu '/home/luken/Pobrane/acs-driver/ACS-Unified-Driver-Lnx-Mac-113-P/acsccid-1.1.3/src'
./create_Info_plist.pl ./supported_readers.txt ./Info.plist.src --target=libacsccid.so --version=1.1.3 --no-class > Info.plist
/bin/sh /home/luken/Pobrane/acs-driver/ACS-Unified-Driver-Lnx-Mac-113-P/acsccid-1.1.3/config/install-sh -d /usr/lib/pcsc/drivers/ifd-acsccid.bundle/Contents/Linux/
cp Info.plist /usr/lib/pcsc/drivers/ifd-acsccid.bundle/Contents/
cp .libs/libacsccid.so /usr/lib/pcsc/drivers/ifd-acsccid.bundle/Contents/Linux/libacsccid.so
/bin/echo -e "\n\33[01;31m***************\n" ; echo "copy the src/92_pcscd_acsccid.rules file in udev directory (/etc/udev/rules.d/)" ; /bin/echo -e "\n***************\n\33[0m"
make[1]: Opuszczenie katalogu '/home/luken/Pobrane/acs-driver/ACS-Unified-Driver-Lnx-Mac-113-P/acsccid-1.1.3/src'
make[1]: Wejście do katalogu '/home/luken/Pobrane/acs-driver/ACS-Unified-Driver-Lnx-Mac-113-P/acsccid-1.1.3'
test -f config.h || rm -f stamp-h1
test -f config.h || make  stamp-h1
make  install-exec-am install-data-am
make[2]: Wejście do katalogu '/home/luken/Pobrane/acs-driver/ACS-Unified-Driver-Lnx-Mac-113-P/acsccid-1.1.3'
make[2]: Nie ma nic do zrobienia w 'install-exec-am'.
make[2]: Nie ma nic do zrobienia w 'install-data-am'.
make[2]: Opuszczenie katalogu '/home/luken/Pobrane/acs-driver/ACS-Unified-Driver-Lnx-Mac-113-P/acsccid-1.1.3'
make[1]: Opuszczenie katalogu '/home/luken/Pobrane/acs-driver/ACS-Unified-Driver-Lnx-Mac-113-P/acsccid-1.1.3'

And here is a content of 92-libacsccid1.rules:

# udev rules for ACS CCID devices

# If not adding the device, go away
ACTION!="add", GOTO="pcscd_acsccid_rules_end"
SUBSYSTEM!="usb", GOTO="pcscd_acsccid_rules_end"
ENV{DEVTYPE}!="usb_device", GOTO="pcscd_acsccid_rules_end"

# set USB power management to auto.
ENV{ID_USB_INTERFACES}==":0b0000:", RUN+="/bin/sh -c 'echo auto > /sys/$devpath/power/control'"

# All done
LABEL="pcscd_acsccid_rules_end"

install-sh file:

#!/bin/sh
# install - install a program, script, or datafile

scriptversion=2014-09-12.12; # UTC

# This originates from X11R5 (mit/util/scripts/install.sh), which was
# later released in X11R6 (xc/config/util/install.sh) with the
# following copyright and license.
#
# Copyright (C) 1994 X Consortium
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to
# deal in the Software without restriction, including without limitation the
# rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
# sell copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
# X CONSORTIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
# AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNEC-
# TION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#
# Except as contained in this notice, the name of the X Consortium shall not
# be used in advertising or otherwise to promote the sale, use or other deal-
# ings in this Software without prior written authorization from the X Consor-
# tium.
#
#
# FSF changes to this file are in the public domain.
#
# Calling this script install-sh is preferred over install.sh, to prevent
# 'make' implicit rules from creating a file called install from it
# when there is no Makefile.
#
# This script is compatible with the BSD install script, but was written
# from scratch.

tab='   '
nl='
'
IFS=" $tab$nl"

# Set DOITPROG to "echo" to test this script.

doit=${DOITPROG-}
doit_exec=${doit:-exec}

# Put in absolute file names if you don't have them in your path;
# or use environment vars.

chgrpprog=${CHGRPPROG-chgrp}
chmodprog=${CHMODPROG-chmod}
chownprog=${CHOWNPROG-chown}
cmpprog=${CMPPROG-cmp}
cpprog=${CPPROG-cp}
mkdirprog=${MKDIRPROG-mkdir}
mvprog=${MVPROG-mv}
rmprog=${RMPROG-rm}
stripprog=${STRIPPROG-strip}

posix_mkdir=

# Desired mode of installed file.
mode=0755

chgrpcmd=
chmodcmd=$chmodprog
chowncmd=
mvcmd=$mvprog
rmcmd="$rmprog -f"
stripcmd=

src=
dst=
dir_arg=
dst_arg=

copy_on_change=false
is_target_a_directory=possibly

usage="\
Usage: $0 [OPTION]... [-T] SRCFILE DSTFILE
   or: $0 [OPTION]... SRCFILES... DIRECTORY
   or: $0 [OPTION]... -t DIRECTORY SRCFILES...
   or: $0 [OPTION]... -d DIRECTORIES...

In the 1st form, copy SRCFILE to DSTFILE.
In the 2nd and 3rd, copy all SRCFILES to DIRECTORY.
In the 4th, create DIRECTORIES.

Options:
     --help     display this help and exit.
     --version  display version info and exit.

  -c            (ignored)
  -C            install only if different (preserve the last data modification time)
  -d            create directories instead of installing files.
  -g GROUP      $chgrpprog installed files to GROUP.
  -m MODE       $chmodprog installed files to MODE.
  -o USER       $chownprog installed files to USER.
  -s            $stripprog installed files.
  -t DIRECTORY  install into DIRECTORY.
  -T            report an error if DSTFILE is a directory.

Environment variables override the default commands:
  CHGRPPROG CHMODPROG CHOWNPROG CMPPROG CPPROG MKDIRPROG MVPROG
  RMPROG STRIPPROG
"

while test $# -ne 0; do
  case $1 in
    -c) ;;

    -C) copy_on_change=true;;

    -d) dir_arg=true;;

    -g) chgrpcmd="$chgrpprog $2"
        shift;;

    --help) echo "$usage"; exit $?;;

    -m) mode=$2
        case $mode in
          *' '* | *"$tab"* | *"$nl"* | *'*'* | *'?'* | *'['*)
            echo "$0: invalid mode: $mode" >&2
            exit 1;;
        esac
        shift;;

    -o) chowncmd="$chownprog $2"
        shift;;

    -s) stripcmd=$stripprog;;

    -t)
        is_target_a_directory=always
        dst_arg=$2
        # Protect names problematic for 'test' and other utilities.
        case $dst_arg in
          -* | [=\(\)!]) dst_arg=./$dst_arg;;
        esac
        shift;;

    -T) is_target_a_directory=never;;

    --version) echo "$0 $scriptversion"; exit $?;;

    --) shift
        break;;

    -*) echo "$0: invalid option: $1" >&2
        exit 1;;

    *)  break;;
  esac
  shift
done

# We allow the use of options -d and -T together, by making -d
# take the precedence; this is for compatibility with GNU install.

if test -n "$dir_arg"; then
  if test -n "$dst_arg"; then
    echo "$0: target directory not allowed when installing a directory." >&2
    exit 1
  fi
fi

if test $# -ne 0 && test -z "$dir_arg$dst_arg"; then
  # When -d is used, all remaining arguments are directories to create.
  # When -t is used, the destination is already specified.
  # Otherwise, the last argument is the destination.  Remove it from $@.
  for arg
  do
    if test -n "$dst_arg"; then
      # $@ is not empty: it contains at least $arg.
      set fnord "$@" "$dst_arg"
      shift # fnord
    fi
    shift # arg
    dst_arg=$arg
    # Protect names problematic for 'test' and other utilities.
    case $dst_arg in
      -* | [=\(\)!]) dst_arg=./$dst_arg;;
    esac
  done
fi

if test $# -eq 0; then
  if test -z "$dir_arg"; then
    echo "$0: no input file specified." >&2
    exit 1
  fi
  # It's OK to call 'install-sh -d' without argument.
  # This can happen when creating conditional directories.
  exit 0
fi

if test -z "$dir_arg"; then
  if test $# -gt 1 || test "$is_target_a_directory" = always; then
    if test ! -d "$dst_arg"; then
      echo "$0: $dst_arg: Is not a directory." >&2
      exit 1
    fi
  fi
fi

if test -z "$dir_arg"; then
  do_exit='(exit $ret); exit $ret'
  trap "ret=129; $do_exit" 1
  trap "ret=130; $do_exit" 2
  trap "ret=141; $do_exit" 13
  trap "ret=143; $do_exit" 15

  # Set umask so as not to create temps with too-generous modes.
  # However, 'strip' requires both read and write access to temps.
  case $mode in
    # Optimize common cases.
    *644) cp_umask=133;;
    *755) cp_umask=22;;

    *[0-7])
      if test -z "$stripcmd"; then
        u_plus_rw=
      else
        u_plus_rw='% 200'
      fi
      cp_umask=`expr '(' 777 - $mode % 1000 ')' $u_plus_rw`;;
    *)
      if test -z "$stripcmd"; then
        u_plus_rw=
      else
        u_plus_rw=,u+rw
      fi
      cp_umask=$mode$u_plus_rw;;
  esac
fi

for src
do
  # Protect names problematic for 'test' and other utilities.
  case $src in
    -* | [=\(\)!]) src=./$src;;
  esac

  if test -n "$dir_arg"; then
    dst=$src
    dstdir=$dst
    test -d "$dstdir"
    dstdir_status=$?
  else

    # Waiting for this to be detected by the "$cpprog $src $dsttmp" command
    # might cause directories to be created, which would be especially bad
    # if $src (and thus $dsttmp) contains '*'.
    if test ! -f "$src" && test ! -d "$src"; then
      echo "$0: $src does not exist." >&2
      exit 1
    fi

    if test -z "$dst_arg"; then
      echo "$0: no destination specified." >&2
      exit 1
    fi
    dst=$dst_arg

    # If destination is a directory, append the input filename; won't work
    # if double slashes aren't ignored.
    if test -d "$dst"; then
      if test "$is_target_a_directory" = never; then
        echo "$0: $dst_arg: Is a directory" >&2
        exit 1
      fi
      dstdir=$dst
      dst=$dstdir/`basename "$src"`
      dstdir_status=0
    else
      dstdir=`dirname "$dst"`
      test -d "$dstdir"
      dstdir_status=$?
    fi
  fi

  obsolete_mkdir_used=false

  if test $dstdir_status != 0; then
    case $posix_mkdir in
      '')
        # Create intermediate dirs using mode 755 as modified by the umask.
        # This is like FreeBSD 'install' as of 1997-10-28.
        umask=`umask`
        case $stripcmd.$umask in
          # Optimize common cases.
          *[2367][2367]) mkdir_umask=$umask;;
          .*0[02][02] | .[02][02] | .[02]) mkdir_umask=22;;

          *[0-7])
            mkdir_umask=`expr $umask + 22 \
              - $umask % 100 % 40 + $umask % 20 \
              - $umask % 10 % 4 + $umask % 2
            `;;
          *) mkdir_umask=$umask,go-w;;
        esac

        # With -d, create the new directory with the user-specified mode.
        # Otherwise, rely on $mkdir_umask.
        if test -n "$dir_arg"; then
          mkdir_mode=-m$mode
        else
          mkdir_mode=
        fi

        posix_mkdir=false
        case $umask in
          *[123567][0-7][0-7])
            # POSIX mkdir -p sets u+wx bits regardless of umask, which
            # is incompatible with FreeBSD 'install' when (umask & 300) != 0.
            ;;
          *)
            # $RANDOM is not portable (e.g. dash);  use it when possible to
            # lower collision chance
            tmpdir=${TMPDIR-/tmp}/ins$RANDOM-$$
            trap 'ret=$?; rmdir "$tmpdir/a/b" "$tmpdir/a" "$tmpdir" 2>/dev/null; exit $ret' 0

            # As "mkdir -p" follows symlinks and we work in /tmp possibly;  so
            # create the $tmpdir first (and fail if unsuccessful) to make sure
            # that nobody tries to guess the $tmpdir name.
            if (umask $mkdir_umask &&
                $mkdirprog $mkdir_mode "$tmpdir" &&
                exec $mkdirprog $mkdir_mode -p -- "$tmpdir/a/b") >/dev/null 2>&1
            then
              if test -z "$dir_arg" || {
                   # Check for POSIX incompatibilities with -m.
                   # HP-UX 11.23 and IRIX 6.5 mkdir -m -p sets group- or
                   # other-writable bit of parent directory when it shouldn't.
                   # FreeBSD 6.1 mkdir -m -p sets mode of existing directory.
                   test_tmpdir="$tmpdir/a"
                   ls_ld_tmpdir=`ls -ld "$test_tmpdir"`
                   case $ls_ld_tmpdir in
                     d????-?r-*) different_mode=700;;
                     d????-?--*) different_mode=755;;
                     *) false;;
                   esac &&
                   $mkdirprog -m$different_mode -p -- "$test_tmpdir" && {
                     ls_ld_tmpdir_1=`ls -ld "$test_tmpdir"`
                     test "$ls_ld_tmpdir" = "$ls_ld_tmpdir_1"
                   }
                 }
              then posix_mkdir=:
              fi
              rmdir "$tmpdir/a/b" "$tmpdir/a" "$tmpdir"
            else
              # Remove any dirs left behind by ancient mkdir implementations.
              rmdir ./$mkdir_mode ./-p ./-- "$tmpdir" 2>/dev/null
            fi
            trap '' 0;;
        esac;;
    esac

    if
      $posix_mkdir && (
        umask $mkdir_umask &&
        $doit_exec $mkdirprog $mkdir_mode -p -- "$dstdir"
      )
    then :
    else

      # The umask is ridiculous, or mkdir does not conform to POSIX,
      # or it failed possibly due to a race condition.  Create the
      # directory the slow way, step by step, checking for races as we go.

      case $dstdir in
        /*) prefix='/';;
        [-=\(\)!]*) prefix='./';;
        *)  prefix='';;
      esac

      oIFS=$IFS
      IFS=/
      set -f
      set fnord $dstdir
      shift
      set +f
      IFS=$oIFS

      prefixes=

      for d
      do
        test X"$d" = X && continue

        prefix=$prefix$d
        if test -d "$prefix"; then
          prefixes=
        else
          if $posix_mkdir; then
            (umask=$mkdir_umask &&
             $doit_exec $mkdirprog $mkdir_mode -p -- "$dstdir") && break
            # Don't fail if two instances are running concurrently.
            test -d "$prefix" || exit 1
          else
            case $prefix in
              *\'*) qprefix=`echo "$prefix" | sed "s/'/'\\\\\\\\''/g"`;;
              *) qprefix=$prefix;;
            esac
            prefixes="$prefixes '$qprefix'"
          fi
        fi
        prefix=$prefix/
      done

      if test -n "$prefixes"; then
        # Don't fail if two instances are running concurrently.
        (umask $mkdir_umask &&
         eval "\$doit_exec \$mkdirprog $prefixes") ||
          test -d "$dstdir" || exit 1
        obsolete_mkdir_used=true
      fi
    fi
  fi

  if test -n "$dir_arg"; then
    { test -z "$chowncmd" || $doit $chowncmd "$dst"; } &&
    { test -z "$chgrpcmd" || $doit $chgrpcmd "$dst"; } &&
    { test "$obsolete_mkdir_used$chowncmd$chgrpcmd" = false ||
      test -z "$chmodcmd" || $doit $chmodcmd $mode "$dst"; } || exit 1
  else

    # Make a couple of temp file names in the proper directory.
    dsttmp=$dstdir/_inst.$$_
    rmtmp=$dstdir/_rm.$$_

    # Trap to clean up those temp files at exit.
    trap 'ret=$?; rm -f "$dsttmp" "$rmtmp" && exit $ret' 0

    # Copy the file name to the temp name.
    (umask $cp_umask && $doit_exec $cpprog "$src" "$dsttmp") &&

    # and set any options; do chmod last to preserve setuid bits.
    #
    # If any of these fail, we abort the whole thing.  If we want to
    # ignore errors from any of these, just make sure not to ignore
    # errors from the above "$doit $cpprog $src $dsttmp" command.
    #
    { test -z "$chowncmd" || $doit $chowncmd "$dsttmp"; } &&
    { test -z "$chgrpcmd" || $doit $chgrpcmd "$dsttmp"; } &&
    { test -z "$stripcmd" || $doit $stripcmd "$dsttmp"; } &&
    { test -z "$chmodcmd" || $doit $chmodcmd $mode "$dsttmp"; } &&

    # If -C, don't bother to copy if it wouldn't change the file.
    if $copy_on_change &&
       old=`LC_ALL=C ls -dlL "$dst"     2>/dev/null` &&
       new=`LC_ALL=C ls -dlL "$dsttmp"  2>/dev/null` &&
       set -f &&
       set X $old && old=:$2:$4:$5:$6 &&
       set X $new && new=:$2:$4:$5:$6 &&
       set +f &&
       test "$old" = "$new" &&
       $cmpprog "$dst" "$dsttmp" >/dev/null 2>&1
    then
      rm -f "$dsttmp"
    else
      # Rename the file to the real destination.
      $doit $mvcmd -f "$dsttmp" "$dst" 2>/dev/null ||

      # The rename failed, perhaps because mv can't rename something else
      # to itself, or perhaps because mv is so ancient that it does not
      # support -f.
      {
        # Now remove or move aside any old file at destination location.
        # We try this two ways since rm can't unlink itself on some
        # systems and the destination file might be busy for other
        # reasons.  In this case, the final cleanup might fail but the new
        # file should still install successfully.
        {
          test ! -f "$dst" ||
          $doit $rmcmd -f "$dst" 2>/dev/null ||
          { $doit $mvcmd -f "$dst" "$rmtmp" 2>/dev/null &&
            { $doit $rmcmd -f "$rmtmp" 2>/dev/null; :; }
          } ||
          { echo "$0: cannot unlink or rename $dst" >&2
            (exit 1); exit 1
          }
        } &&

        # Now rename the file to the real destination.
        $doit $mvcmd "$dsttmp" "$dst"
      }
    fi || exit 1

    trap '' 0
  fi
done

# Local variables:
# eval: (add-hook 'write-file-hooks 'time-stamp)
# time-stamp-start: "scriptversion="
# time-stamp-format: "%:y-%02m-%02d.%02H"
# time-stamp-time-zone: "UTC"
# time-stamp-end: "; # UTC"
# End:
9
  • 1
    This is not actually a driver and Linux doesn't guess it. The installation step includes instructions to load the newly built daemon: pcscd. – Julie Pelletier Aug 12 '16 at 16:41
  • Which line should I look at? – Łukasz Zaroda Aug 12 '16 at 16:55
  • I'd guess it's done in /home/luken/Pobrane/acs-driver/ACS-Unified-Driver-Lnx-Mac-113-P/acsccid-1.1.3/config/install-sh. – Julie Pelletier Aug 12 '16 at 17:06
  • I added content of install-sh file. It doesn't seem to me that this file is doing more than providing some compatibility during installation or something like that. – Łukasz Zaroda Aug 12 '16 at 17:10
  • 1
    Are you sure the pcscd daemon is already set to load automatically? That would imply some init configurations such as ludovicrousseau.blogspot.ca/2011/11/… – Julie Pelletier Aug 12 '16 at 17:25
0

Linux drivers run in the kernel. In addition to the drivers that are included in the kernel image when the system starts, some drivers are loaded as modules. There are some very common classes of drivers that can be loaded when the corresponding device is detected (see Debian does not detect serial PCI card after reboot). Other drivers need to be loaded explicitly. Some hardware can be probed, and so the driver will probe for supported hardware. Some hardware can't be probed (fortunately they are extremely rare on PC and uncommon even in the embedded world), and the driver has to be told how the hardware device is connected to the computer.

Only the kernel can talk to hardware — this is a basic security restriction. However, it's possible for the kernel driver to set up a communication mechanism with a userland program, and then the userland program acts as part of a driver. This happens with graphical displays, where part of the video card driver executes inside the X server process. This also happens with access control smartcards, for which the kernel driver handles the low-level communication protocol and the pcscd program handles high-level commands.

When some driver functionality is offloaded to a userland program, there's no standard method by which hardware-dependent driver components are chosen. It depends on the program.

In the case of pcscd, reader-specific code is loaded as a shared library (.so file) under /usr/lib/pcsc/drivers. Serial readers require an entry in /etc/reader.conf.d/reader.conf; USB readers are automatically detected. So merely dropping the .so file in the directory is sufficient: when pcscd starts, it loads all the libraries in that directory and calls a known entry point to detect matching hardware. This is the same approach that X.org uses; it's a sensible design, but not the only possible one.

udev rules are primarily used to create device files which allow programs to access hardware managed by the kernel, and set the permissions on these device files. In the case of USB smartcard readers, I think a generic USB access interface is used, which doesn't use device files but rather files under /sys/bus/usb/devices/*.

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