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

[Bill Davidsen <davidsen@tmr.com>]

Matthias Andree wrote:
> On Sat, 18 Feb 2006, D. Hazelton wrote:
>
> > Well, in this case I'm actually trying to work with Joerg to produce a patch 
> > that unifies the ATAPI and SCSI busses inside his program.
>
> This patch already exists, see:
> <http://www.ussg.iu.edu/hypermail/linux/kernel/0602.0/1103.html>
>
> It's a proof of concept and needs to be polished (I'll look into that
> again in March).
>
> Only it still probes all /dev/hd and /dev/sg and /dev/pg in a dumb way,
> rather than looking at sysfs or reading through /dev/.
>
> > I've seen the "MRW" stuff in some of the specs, but had to check the net to 
> > find out what it was. MRW is the Mt. Rainier format - basic support was added 
> > by Jens back in 2.4.19 according to the archives. 
> > (http://www.ussg.iu.edu/hypermail/linux/kernel/0203.2/1214.html)
> >
> > I'm not positive, but the "Can Read RAM" line might refer to DVD-RAM type 
> > discs
>
> That's probably not it, since there's a separate DVD-RAM line here:
>
> CD-ROM information, Id: cdrom.c 3.20 2003/12/17
>
> drive name:             hdd     hdc     sr0
> drive speed:            40      48      1
> drive # of slots:       1       1       1
> Can close tray:         1       1       1
> Can open tray:          1       1       1
> Can lock tray:          1       1       1
> Can change speed:       1       1       0
> Can select disk:        0       0       0
> Can read multisession:  1       1       1
> Can read MCN:           1       1       1
> Reports media changed:  1       1       1
> Can play audio:         1       1       1
> Can write CD-R:         1       1       0
> Can write CD-RW:        1       1       0
> Can read DVD:           0       1       0
> Can write DVD-R:        0       1       0
> Can write DVD-RAM:      0       1       0
> Can read MRW:           1       1       1
> Can write MRW:          1       1       1
> Can write RAM:          1       1       1
>
> hdd = Plextor PX-W4824TA
> hdc = NEC ND-4550A
> sr0 = Plextor PX-32TS

Other than my 2.6.15 not producing those last three lines, looks good.
The names are those in /sys, which of course many distros change in udev
to make things hard for the user. Hard t write an app portably to cope
with /dev/scd0, /dev/sr0, /dev/cdroms/sr0, etc.

I am NOT suggesting changing a stable interface, but this really should
be in /sys I would think. It would be nice to have the major/minor and
model info, so programs could find the "better" named in /dev or just
mknod their own.
> (Now NEC only needs to teach their drives to be more error tolerant when
> reading and adjust their read speed to the actual sustained transfer
> rate as Toshiba drives have been doing for ages...)

This would appear to be almost all the user needs to at least find the
devices. I don't know why no one mentioned it several years ago.

--
   -bill davidsen (davidsen@tmr.com)
"The secret to procrastination is to put things off until the
 last possible moment - but no longer"  -me

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