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    SubjectRe: CD writing in future Linux (stirring up a hornets' nest)
    jerome lacoste <jerome.lacoste@gmail.com> wrote:

    > On 2/10/06, Joerg Schilling <schilling@fokus.fraunhofer.de> wrote:
    > > "D. Hazelton" <dhazelton@enter.net> 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 ?

    b,t,l _is_ stable as long as the OS does a reasonable and orthogonal work.

    This was true until ~ 2001, when Linux introduced unstable USB handling.
    Note that this fact is not a failure from libscg but from Linux.


    > 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.

    The output of cdrecord -scanbus is already parsable, so what is your point?

    Jörg

    --
    EMail:joerg@schily.isdn.cs.tu-berlin.de (home) Jörg Schilling D-13353 Berlin
    js@cs.tu-berlin.de (uni)
    schilling@fokus.fraunhofer.de (work) Blog: http://schily.blogspot.com/
    URL: http://cdrecord.berlios.de/old/private/ ftp://ftp.berlios.de/pub/schily
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