Messages in this thread | | | Date | Tue, 19 May 1998 18:08:11 +1000 | From | Richard Gooch <> | Subject | Re: Poor device management |
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John Goerzen writes: > I would like to address the topic of naming of devices. Currently, we > have two serious problems:
I agree.
> 1. It appears that Linux can support a maximum of 16 SCSI hard drives > per system, according to devices.txt. > > This is a serious issue as we would like to have more than that on > some machines but the OS does not appear to support that. The > allocated block of device numbers appears to have no support for more.
Jakub did something with the VGER tree to support many SCSI discs. I think it required some new system calls (to deal with larger device numbers). There is a technique you could implement using devfs which doesn't require new system calls (see the devfs FAQ).
> 2. Device numbers can change between boots or even during operation. > > This is because the device numbers (and thus, /dev entries) are > allocated in sequential order. Thus, for instance, if my Jaz drive > (SCSI ID 4) is turned off but my scanner (ID 5) is on, the scanner > gets a particular device assigned to it. However, it the Jaz drive is > on when the system boots, the Jaz gets that ID and the scanner gets > something different. > > It would, therefore, be highly advisable to go to something akin to > Solaris -- the /dev entries specify controller, target, and LUN > expliticly. This will remove a lot of confusion especially > surrounding the sg devices and eliminate the problem of drifting > device entries.
This (point (2)) is already done: it's called devfs. Check out: http://www.atnf.csiro.au/~rgooch/linux/
and navigate to my kernel patches for 2.1. There you'll see links to the devfs patch and the devfs FAQ.
Regards,
Richard....
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