devfs-enabled kernels and /proc/partitions

[Colin Walters <walters@debian.org>]

Currently, the boot-floppies can't deal with a kernel which has
CONFIG_DEVFS_FS=y, even if CONFIG_DEVFS_MOUNT is not set.  I tracked
this down to libfdisk not liking the devfs /proc/partitions.

I started to write a little C function which translated the names,
and this is fairly trivial for IDE.  However, it is not so trivial
for SCSI.

So, we could just try to ensure that b-f will never be booted with a
DevFS-enabled kernel, but I think this is a bad idea.

I found a function to do the conversion, but it is written in shell;
popening /bin/sh in the middle of libfdisk seems really gross to
me...does anyone know of a C function somewhere we could snarf?  If
not, I guess I can just send a patch to do the former.

For reference, here's the shell function in question:

## convert devfs names into normal short ones, written by Tom Rini.
fixdevfs()
{
    ## get partition number, if any
    local PARTNUM="${1##*[a-z]}"
    ## Find the bus type.
    local TYPE="$(v=${1#/dev/} ; echo ${v%/host*})"
    ## Find the host number.
    local HOST="$(v=${1#/dev/*/host} ; echo ${v%/bus*})"
    ## Find the bus number.
    local BUS="$(v=${1#/dev/*/bus} ; echo ${v%/tar*})"
    ## Find the target.
    local TARGET="$(v=${1#/dev/*/target} ; echo ${v%/lun*})"

    case "$TYPE" in
	ide)
	case "$HOST" in
	    0)
	    case "$TARGET" in
		0)
		local DEV=hda
		;;
		1)
		local DEV=hdb
		;;
	    esac
	    ;;
	    1)
	    case "$TARGET" in
		0)
	        local DEV=hdc
	        ;;
		1)
		local DEV=hdd
		;;
	    esac
	    ;;
	    *)
		echo 1>&2 "$PRG: $1: Unable to translate this device, try again without devfs."
		return 1
	esac
	local DEV="${DEV}${PARTNUM}"
	echo "/dev/$DEV"
	return 0
	;;
	scsi)
	local LUN="$(v=${1#/dev/*/lun} ; echo ${v%/*})"

	## In this case, we need to figure out what number our device is
	local DEVCOUNT=0

	## copy scsi file into a variable removing "Attached Devices"
	## which is the first line. this avoids a lot of
	## [incmopatible] crap later, and improves readability.

	## find number of lines once and recycle that number, to save
	## some time (linecount is a bit slow). subtract one line
	## to scrap Attached Devices:

	local SCSILINES="$(($(linecount /proc/scsi/scsi) - 1))"
	local PROCSCSI="$(cat /proc/scsi/scsi | tail -n $SCSILINES)"

	for i in $(smallseq $(($SCSILINES / 3))) ; do

	    ## put every scsi device into one single line
	    local DEVINFO="$(echo "$PROCSCSI" | head -n $(($i * 3)) | tail -n 3)"
	    [ "$DEBUG" = 1 ] && echo 1>&2 "$PRG: DEBUG: fixdevfs: DEVINFO=$DEVINFO"

	    ## cut the type field, expect "Direct-Access" later.
	    local DEVTYPE="$(v=$(echo ${DEVINFO##*Type: }) ; echo ${v%% *})"
	    [ "$DEBUG" = 1 ] && echo 1>&2 "$PRG: DEBUG: fixdevfs: DEVTYPE=$DEVTYPE"

	    if [ "$DEVTYPE" = "Direct-Access" ] ; then
		## Lets find out some more information
		## get the device id.
		local DEVID="$(v=$(echo ${DEVINFO##*Id: }) ; n=$(echo ${v%% *}) ; echo ${n#*0})"
		[ "$DEBUG" = 1 ] && echo 1>&2 "$PRG: DEBUG: fixdevfs: DEVID=$DEVID"

		## get the device lun.
		local DEVLUN="$(v=$(echo ${DEVINFO##*Lun: }) ; n=$(echo ${v%% *}) ; echo ${n#*0})"
		[ "$DEBUG" = 1 ] && echo 1>&2 "$PRG: DEBUG: fixdevfs: DEVLUN=$DEVLUN"

		## get the device channel.
		local DEVCHAN="$(v=$(echo ${DEVINFO##*Channel: }) ; n=$(echo ${v%% *}) ; echo ${n#*0})"
		[ "$DEBUG" = 1 ] && echo 1>&2 "$PRG: DEBUG: fixdevfs: DEVCHAN=$DEVCHAN"

		## get the scsi host id.
		local DEVHOST="$(v=$(echo ${DEVINFO##*Host: scsi}) ; echo ${v%% *})"
		[ "$DEBUG" = 1 ] && echo 1>&2 "$PRG: DEBUG: fixdevfs: DEVHOST=$DEVHOST"

		local DEVCOUNT="$(($DEVCOUNT + 1))"
		[ "$DEBUG" = 1 ] && echo 1>&2 "$PRG: DEBUG: fixdevfs: DEVCOUNT=$DEVCOUNT"
		if [ "$DEVHOST" = "$HOST" -a "$DEVCHAN" = "$BUS" -a \
		    "$DEVID" = "$TARGET" -a "$DEVLUN" = "$LUN" ] ; then
		    local DEV="sd$(smalltr $DEVCOUNT)${PARTNUM}"
		    echo "/dev/$DEV"
		    return 0
		fi
	    fi
	done
	echo 1>&2 "$PRG: $1: Unable to translate this device, try again without devfs."
	return 1
	;;
	*)
	echo 1>&2 "$PRG: Unknown bus $TYPE"
	return 1
	;;
    esac
    ## we should never get here
    return 1
}