> Date: Mon, 16 Oct 95 22:18 EDT
> From: Eric Youngdale <eric@aib.com>
> To: Dan Merillat <harik@accessorl.net>
> Cc: Jeremiah Jahn <jeremiah@litoria.math.earlham.edu>,
> linux-kernel@vger.rutgers.edu
> Subject: Re: multiple scsi drives..
>
>
> >I take it then that there is still no way to grab the driver
> > by controller:deviceid? I'd rather have scsi/ have devices
> > of the type scsi/[a-d][1-7][1-40?] then devices that get changed
>
> The utility that I described generates entries like:
> crw------- 1 root root 9, 128 Aug 4 13:16 rsth4c0i5l0
^^^^^^^^^^^
I take it this is rewinding scsi-tape right? It's the only one that
dosn't follow the pattern of the rest.
[more examples snipped]
>
> Given entries like this, then it is possible to grab devices
> by controller:deviceid. The numbers for disks are
>
> sdh4 - disk, attached to host type 4 (i.e. aha1542).
> -334 - identifies which 1542, in this case the I/O port it is using.
> c0 - channel 0 (1542 only has one chan, others have more than 1)
> i0 - scsi id 0
> l0 - scsi lun 0
> p1 - partition 1
Very nice. This is what I was looking for, even if the device numbers
change.
> If you are asking about a fixed mapping of minor numbers to
> devices, then this is not possible with a 16 bit dev_t (where you have
> 8 bits for the minor). With a 32 bit dev_t, it is still easily
> arguable that you do not have enough dynamic range to cover all of the
> possibilities without making assumptions about the ranges of some of
> the numbers, esp if you split it 16/16. I have even seen someone
> argue that you need about 48 bits for the minor number to allow for
> all of the possible permutations involving disk drives.
I know the argument. I had forgotten about multi-lun devices. I figured
8 channels + 8 devices/channel is 8 bits right there, plenty for the minor
number.
>
> If and when a larger dev_t is implemented, we might recondsider
> and attempt to implement a fixed-mapping for scsi, but as of the moment
> there are no plans to change the mapping.
Well, I still have yet to see a machine running linux with more then 255
devices on it, so dynamic mapping should be ok. (at least untill we get
raid devices. I'd love to see a linux box serving for a terrabyte-tower.)
Thanks for the info, I'll check your package out.
Dan Merillat <Dan.Merillat@eola.accessorl.net>
Animaniac! Linux Activist and net.junkie
Also at: <drm89121@pegasus.cc.ucf.edu>