[PATCH] mount -w of dvd+rw etc. in vanilla 2.6

[PATCH] mount -w of dvd+rw etc. in vanilla 2.6

[Pat LaVarre]

I see mount -w -t udf works with my dvd-ram in
late Linux 2.4 and early 2.6, but mistakenly
sees my dvd+rw as read-only.

To make my dvd+rw work, I find I can apply
patches much like:
http://fy.chalmers.se/~appro/linux/DVD+RW/
http://fy.chalmers.se/~appro/linux/DVD+RW/linux-2.4.patch

Can I somehow help ... to get a patch like this
finished & merged into the kernel.org kernel?

I'm new to drivers/scsi/sr_vendor.c ... but I
first glanced thru www.t10.org back in 1994.

Looks to me like this patch begins to expand the
awareness of Linux beyond the "mode page" x2A of
dvd-ram/cd-rw into the "profile"s and "feature"s
that distinguish dvd+rw etc. from other dvd/cd,
so that with my dvd+rw I achieve:

scsi_CDs[minor].device->writeable = 1;
scsi_CDs[minor].cdi.mask &= ~CDC_DVD_RAM;

In particular, in the patch I see 3 mmc3_profile
values from among the 7 values that mmc4r02c.pdf
says imply the "feature" "0020h" =
"Random Writable".

Can I help somehow?

Pat LaVarre
http://members.aol.com/plscsi/tools/knoppix/

P.S. Reply-to-all will reach me faster than
reply to p.lavarre@ieee.org or linux-scsi alone.


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Re: [PATCH] mount -w of dvd+rw etc. in vanilla 2.6

[Pat LaVarre]

> mount -w -t udf works with my dvd-ram ...
> mistakenly sees my dvd+rw as read-only ...

Besides that Andy Polyakov patch for mount -w of dvd+rw, the web has
Jens Axboe patches for mount -w of cd-rw, via the udf faq (Not via the
udftools faq):

http://sourceforge.net/projects/linux-udf/
udf-0.9.7.tar.gz
FAQ
http://w1.894.telia.com/~u89404340/patches/packet/

---

>From these two clues, kindly offline people have identified the Four
fragments of kernel source that cooperate to conclude erroneously that
dvd+rw etc. are not writable:

1)

drivers/scsi/sr.c understands only the CDC_DVD_RAM profile of the seven
standard mmc "writable" device "profile"s, because sr.c neglects to look
beyond the "Capabilities" mode page x2a i.e. does not look beyond the
mmc 1 standard of 1997.  Ansi did not publish an op x46 Get
Configuration standard until the mmc 2 of 1999.

2)

include/scsi/scsi.h does not yet #define GET_CONFIGURATION 0x46.

3)

drivers/cdrom/cdrom.c also understands only CDC_DVD_RAM: cdrom.c
erroneously claims all mmc profiles except CDC_DVD_RAM are not
FMODE_WRITE-able.

4)

include/linux/cdrom.h names only CDC_DVD_RAM.

---

Anyone have an idea of how best to patch this?

I've seen a few linux-2.6.0-test4/ and linux-2.4.22/ alternatives mostly
work.  Anyone interested in evaluating some of them?

Pat LaVarre

Re: [PATCH] mount -w of dvd+rw etc. in vanilla 2.6

[Pat LaVarre]

Seemingly linux disagrees with itself over how writable profiles are:

# /sbin/blockdev --setro /dev/scd1
# /sbin/blockdev --getro /dev/scd1
1
# dd of=/dev/scd1 if=/dev/zero bs=2K count=1
dd: opening `/dev/scd1': Read-only file system
#

So far so good, but then:

# /sbin/blockdev --setrw /dev/scd1
# /sbin/blockdev --getro /dev/scd1
0
# dd of=/dev/scd1 if=/dev/zero bs=2K count=1
dd: opening `/dev/scd1': Read-only file system
#

That is, no matter if --getro is 0 or 1, still we do not write.  The
default I see here is 0, but still I cannot write.

Pat LaVarre

Re: [PATCH] mount -w of dvd+rw etc. in vanilla 2.6

[Patrick Mansfield]

On Wed, Sep 10, 2003 at 02:08:40PM -0600, Pat LaVarre wrote:

> # /sbin/blockdev --setro /dev/scd1
> # /sbin/blockdev --getro /dev/scd1
> 1
> # dd of=/dev/scd1 if=/dev/zero bs=2K count=1
> dd: opening `/dev/scd1': Read-only file system
> #
> 
> So far so good, but then:
> 
> # /sbin/blockdev --setrw /dev/scd1
> # /sbin/blockdev --getro /dev/scd1
> 0
> # dd of=/dev/scd1 if=/dev/zero bs=2K count=1
> dd: opening `/dev/scd1': Read-only file system
> #
> 
> That is, no matter if --getro is 0 or 1, still we do not write.  The
> default I see here is 0, but still I cannot write.

Should sd.c and sr.c be calling set_device_ro (after adding a read only
block device, or changing back to read/write)?

-- Patrick Mansfield