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Date:   Wed, 4 Jan 2023 21:56:40 +0100
From:   Pali =?utf-8?B?Um9ow6Fy?= <pali@kernel.org>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Linux 6.2-rc1
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On Wednesday 04 January 2023 11:25:41 Linus Torvalds wrote:
> On Wed, Jan 4, 2023 at 11:01 AM Pali Rohár <pali@kernel.org> wrote:
> >
> > Driver is still used and userspace tools for it are part of the udftools
> > project, which is still under active maintenance. More people already
> > informed me about this "surprise".
> 
> Why is that driver used?
> 
> It's *literally* pointless. It's just a shell that forwards ioctl's to
> the real drivers.
> 
> > Any comments on this? Because until now nobody answered why this
> > actively used driver was removed from kernel without informing anybody:
> 
> Well, it's been marked as deprecated for five years, so any kernel
> config should have gotten this notice for the help entry
> 
>           Note: This driver is deprecated and will be removed from the
>           kernel in the near future!
> 
> but I guess people didn't notice.
> 
> It could be re-instated, but it really is a completely useless driver.
> Just use the *regular* device nodes, not the pointless pktcd ones.
> 
> Is there any real reason why udftools can't just use the normal device node?
> 
> The historical reason for this driver being pointless goes back *much*
> longer than five years - it used to be that the pktcd driver was
> special, and was the only thing that did raw commands.
> 
> But the regular block layer was taught to do that back around 2004, so
> the "pktcd" driver has literally just been a pointless shell for
> almost two decades.
> 
> And I know it was in 2004, because I actually did most of that "make
> SCSI commands generic" work myself (but had to go back to the old BK
> archives to find the exact date - it's been two decades, after all).
> 
> I did it because I was fed up with the crazy pktcd driver requiring
> extra work, when I just wanted to write CD's on my regular IDE CD-ROM
> the obvious way.
> 
> So if there is some reason to actually use the pktcd driver, please
> tell us what that is.
> 
>               Linus

Last time I did big retest of optical media was two years ago. At that
time kernel was not able to mount CD-RW disc in full read-write mode
from the normal node /dev/cdrom. Via pktcdvd driver mapping it was
possible without any issue. Was there any change in last 5 (or more)
years in this CD-RW area? Mounting CD-RW media in read-only mode via
normal /dev/cdrom node always worked fine. Also "burning" CD-R media
with userspace burning tools on normal /dev/cdrom node also worked.
But here it is CD-RW media in read-write mode with kernel udf filesystem
driver without any userspace involved (after proper formatting).