Re: CD writing in future Linux (stirring up a hornets' nest)

[D. Hazelton]

On Friday 10 February 2006 10:38, jerome lacoste wrote:
> On 2/10/06, Joerg Schilling <schilling@xxxxxxxxxxxxxxxxxxx> wrote:
> > "D. Hazelton" <dhazelton@xxxxxxxxx> wrote:
> > > And does cdrecord even need libscg anymore? From having actually gone
> > > through your code, Joerg, I can tell you that it does serve a larger
> > > purpose. But at this point I have to ask - besides cdrecord and a few
> > > other _COMPACT_ _DISC_ writing programs, does _ANYONE_ use libscg? Is
> > > it ever used to access any other devices that are either SCSI or use a
> > > SCSI command protocol (like ATAPI)?  My point there is that you have a
> > > wonderful library, but despite your wishes, there is no proof that it
> > > is ever used for anything except writing/ripping CD's.
> >
> > Name a single program (not using libscg) that implements user space SCSI
> > and runs on as many platforms as cdrecord/libscg does.
>
> I have 2 technical questions, and I hope that you will take the time
> to answer them.
>
> 1) extract from the README of the latest stable cdrtools package:
>
>         Linux driver design oddities
> ****************************************** Although cdrecord supports to
> use dev=/dev/sgc, it is not recommended and it is unsupported.
>
>         The /dev/sg* device mapping in Linux is not stable! Using
> dev=/dev/sgc in a shell script may fail after a reboot because the device
> you want to talk to has moved to /dev/sgd. For the proper and OS
> independent dev=<bus>,<tgt>,<lun> syntax read the man page of cdrecord.
>
> My understanding of that is you say to not use dev=/dev/sgc because it
> isn't stable. Now that you've said that bus,tgt,lun is not stable on
> Linux (because of a "Linux bug") why is the b,t,l scheme preferred
> over the /dev/sg* one ?

Excellent question. Well Joerg, can you give us a good answer, or will it be 
more finger pointing, mud slinging and FUD ?

>
> 2) design question:
>
> - cdrecord scans then maps the device to the b,t,l scheme.
> - the libsg uses the b,t,l ids in its interface to perform the operations
>
> So now, if cdrecord could have a new option called -scanbusmap that
> displays the mapping it performs in a way that people can parse the
> output, I think that will solve most issues.

I'm wondering this myself. If Joerg didn't seem to think everyone in the world 
was an idiot I'd attempt this myself and submit it.

> cdrecord already has this information available, it just doesn't display
> it:
>
> $ cdrecord debug=2 dev=ATAPI -scanbus 2>&1 | grep INFO
> INFO: /dev/hdc, (host0/bus1/target0/lun0) will be mapped on the
> schilly bus No 0 (0,0,0)
> INFO: /dev/hdd, (host0/bus1/target1/lun0) will be mapped on the
> schilly bus No 0 (0,1,0)
>
> It could perform in the following way:
>
> $ cdrecord dev=ATAPI  -scanbusmap
> ...
>
> 0,0,0 <= /dev/hdc
> 0,1,0 <= /dev/hdd
>
>
> Are you accepting such a patch?

If his response to the last patch someone provided is any example the answer 
is going to be no. And I firmly believe the old adage that a leopard can't 
change it's spots.

> Jerome


DRH
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