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Date:      Sat, 20 Mar 1999 01:12:36 -0700
From:      "Justin T. Gibbs" <gibbs@plutotech.com>
To:        Mike Smith <mike@smith.net.au>
Cc:        "Justin T. Gibbs" <gibbs@plutotech.com>, Robert Nordier <rnordier@nordier.com>, current@FreeBSD.org
Subject:   Re: How to add a new bootdevice to the new boot code ??? 
Message-ID:  <199903200821.BAA21142@pluto.plutotech.com>
In-Reply-To: Your message of "Fri, 19 Mar 1999 14:43:09 PST." <199903192243.OAA07306@dingo.cdrom.com> 

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>> In article <199903171103.NAA13749@ceia.nordier.com> you wrote:
>> > S=F8ren Schmidt wrote:
>> >  =

>> >> OK, easy enough, this is what I want to do:
>> >> =

>> >> Boot from an ata disk on major# 30, device name "ad", plain and sim=
ple.
>> > =

>> > I'd be inclined to handle this outside the boot code, by treating th=
e
>> > passed in major# as describing the device rather than specifying
>> > the driver.
>> =

>> Why not have the boot blocks pass in a device 'name' rather than a
>> major number.  If the goal is to ditch major numbers entirely with
>> a properly working DEVFS, then using major numbers in the new boot
>> loader seems to be the wrong way to go.  Until DEVFS is a reality,
>> the kernel will still need to perform a name to major number translati=
on,
>> but it should be left up to the kernel.
>
>Because there's no way to work out a name either.

If I explicitly say:

1:foobar(0,a)/kernel

there certainly is a way to work out the name.  Perhaps in the autoboot
case you'll have to guess, but it would be nice if the current boot
mechanism allowed user intervention as a way to boot a kernel with an
unknown bdev.

>All the loader has to go on is the BIOS unit number and the disklabel, =

>the latter of which can't be relied on to be up-to-date (ie. it =

>reflects what the disk was when it was laid out, not what some nominal =

>kernel is going to call it).

Well, the disklabel format should be revamped so that we can tag devices
in a unique fashion (user's pet name for the partition plus a 128bit
random number perhaps).  This would allow the boot loader to alway tell
the kernel unambiguously how to find the root device.  It would also
allow us to ensure that the attach order for all devices with a BSD
label matched the BIOS probe order.  I would also love to be able
to mount volumes by the name that I've picked for them rather than
by device node too - it would practically eliminate the need for hard
wiring of devices.

--
Justin




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