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Date: Sun, 16 Sep 2001 11:22:21 +0200
From: Corinna Vinschen <vinschen AT redhat DOT com>
To: cygdev <cygwin-developers AT cygwin DOT com>
Subject: Fixed device names
Message-ID: <20010916112221.B15312@cygbert.vinschen.de>
Reply-To: cygdev <cygwin-developers AT cygwin DOT com>
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Hi,

for a long time I'm thinking about giving fixed device names
to the devices which are handled by the fhandler_dev_raw and 
subsequent classes.  I don't like the solution that these    
devices have to have mount table entries and I would like to get
rid of them.

The new device name mapping using fixed names could work as follows
(note that it works on NT systems anyway):

Floppies:

/dev/fd0, /dev/rfd0 -> map to NT internal name "\device\floppy0".
QueryDosDevice("\device\floppy0") returns "A:"  -> \\.\A:

CD-ROMs:

/dev/cdrom1 -> map to NT internal name "\device\cdrom1".
QueryDosDevice("\device\cdrom1") returns some "X:"  ->  \\.\X:

Tapes:

/dev/st2, /dev/nst2  -> map to NT internal name "\device\tape2".
QueryDosDevice("\device\tape2") returns "TAPE2"  ->  \\.\TAPE2

Disks:

/dev/hdd  -> map to NT internal name "\device\harddisk3\partition0"
(NT) or "\device\harddisk3\dr3" (W2K/XP).
QueryDosDevice("\device\harddisk3\...") returns "PhysicalDrive3"
-> \\.\PhysicalDrive3

Partitions:

/dev/hde1 -> thats tricky from W2K on:

Up to NT4 mapped to the NT internal name "\device\harddisk4\partition1".
QueryDosDevice("\device\harddisk4\partition1") returns some "X:" -> \\.\X:

from W2K on:
        h = CreateFile("\\.\physicaldrive4");
        DeviceIoControl(h, IOCTL_DISK_GET_DRIVE_LAYOUT, ...);
          returns structure containing drive signature.
        QueryDosDevice() to get list of entries with NT internal
          name "\device\harddiskvolumeX". There are at least
          three entries per partition.  One of these entries
          contains the drive signature and an offset. Take  
          the partition with the matching offset, grab the   
          matching entry for that volume which contains the  
          drive letter -> \\.\X:      or which contains the
          unique ID -> \\?\Volume{GUID}

That could be easier again from XP on since XP adds the useful
IOCTL_DISK_GET_DRIVE_LAYOUT_EX code which returns the partition
list including the GUIDs of the partitions. The QueryDosDevice
call and the messing around with the drive signature could be
dropped then.

What do you think?  Would you like that?  Do you have a better idea?

Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Developer                                mailto:cygwin AT cygwin DOT com
Red Hat, Inc.