lfs-book-zh_CN/udev-lfs/rule_generator.functions

# functions used by the udev rule generator

# Copyright (C) 2006 Marco d'Itri <md@Linux.IT>
# Updated for LFS by Bruce Dubbs <bdubbs@linuxfromscratch.org>
#  Hardcoded RUNDIR

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 2 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

PATH='/usr/bin:/bin:/usr/sbin:/sbin'

# Read a single line from file $1 in the $DEVPATH directory.
# The function must not return an error even if the file does not exist.
sysread() {
        local file="$1"
        [ -e "/sys$DEVPATH/$file" ] || return 0
        local value
        read value < "/sys$DEVPATH/$file" || return 0
        echo "$value"
}

sysreadlink() {
        local file="$1"
        [ -e "/sys$DEVPATH/$file" ] || return 0
        readlink -f /sys$DEVPATH/$file 2> /dev/null || true
}

# Return true if a directory is writeable.
writeable() {
        if ln -s test-link $1/.is-writeable 2> /dev/null; then
                rm -f $1/.is-writeable
                return 0
        else
                return 1
        fi
}

# Create a lock file for the current rules file.
lock_rules_file() {
        RUNDIR=/run/udev
        [ -e "$RUNDIR" ] || return 0

        RULES_LOCK="$RUNDIR/.lock-${RULES_FILE##*/}"

        retry=30
        while ! mkdir $RULES_LOCK 2> /dev/null; do
                if [ $retry -eq 0 ]; then
                         echo "Cannot lock $RULES_FILE!" >&2
                         exit 2
                fi
                sleep 1
                retry=$(($retry - 1))
        done
}

unlock_rules_file() {
        [ "$RULES_LOCK" ] || return 0
        rmdir $RULES_LOCK || true
}

# Choose the real rules file if it is writeable or a temporary file if not.
# Both files should be checked later when looking for existing rules.
choose_rules_file() {
        RUNDIR=/run/udev
        local tmp_rules_file="$RUNDIR/tmp-rules--${RULES_FILE##*/}"
        [ -e "$RULES_FILE" -o -e "$tmp_rules_file" ] || PRINT_HEADER=1

        if writeable ${RULES_FILE%/*}; then
                RO_RULES_FILE='/dev/null'
        else
                RO_RULES_FILE=$RULES_FILE
                RULES_FILE=$tmp_rules_file
        fi
}

# Return the name of the first free device.
raw_find_next_available() {
        local links="$1"

        local basename=${links%%[ 0-9]*}
        local max=-1
        for name in $links; do
                local num=${name#$basename}
                [ "$num" ] || num=0
                [ $num -gt $max ] && max=$num
        done

        local max=$(($max + 1))
        # "name0" actually is just "name"
        [ $max -eq 0 ] && return
        echo "$max"
}

# Find all rules matching a key (with action) and a pattern.
find_all_rules() {
        local key="$1"
        local linkre="$2"
        local match="$3"

        local search='.*[[:space:],]'"$key"'"('"$linkre"')".*'
        echo $(sed -n -r -e 's/^#.*//' -e "${match}s/${search}/\1/p" \
                $RO_RULES_FILE \
                $([ -e $RULES_FILE ] && echo $RULES_FILE) \
                2>/dev/null)
}