Messages in this thread | | | Date | Thu, 5 Jan 2023 18:42:10 +0100 | From | Pali Rohár <> | Subject | Re: Linux 6.2-rc1 |
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On Wednesday 04 January 2023 14:43:16 Jens Axboe wrote: > On 1/4/23 2:32?PM, Linus Torvalds wrote: > >> But here it is CD-RW media in read-write mode with kernel udf > >> filesystem driver without any userspace involved (after proper > >> formatting). > > > > ... but I'm not sure about direct writeable mount support. > > > > That may indeed be an area that only pktcdvd ended up doing. I've > > never used it myself, even historically. > > > > Let's bring in more people. Because they may not have thought about > > some RW UDF case. > > We did think about it, since that's the only reason for pktcdvd to > exist. Basically what the driver does is ensure that any write is 32K in > size, which is the size which can be written to media. It'll gather data > as needed to make that happen. Thats it. Outside of that, it's just some > setup and closing code. > > This obviously would be better to handle in userspace, all of it. Back > when I wrote this driver, we didn't have a lot of the fancier stuff we > have today. It could be done via ublk, for example, or something like > that. > > The surprising bit here is: > > 1) Someone is still using this driver, and > 2) It actually works!
Yes, there are still users and userspace tools (cdrwtool / pktsetup) are still receiving either small patches or issue reports. I think that it was two years ago when cdrwtool received big fixups to support formatting CD-RW discs on new CD/DVD drives.
> While I'd love to nudge folks in other directions for this use case, and > I strongly think that we should, it also doesn't seem fair to just yank > it while folks are using it... But I'd like to VERY strongly encourage > folks to come up with a new solution for this use case. It really isn't > a solution that belongs in the kernel today.
Linus in previous email wrote that he did "make SCSI commands generic" work in past so direct usage of /dev/cdrom device works for CD-R burning and read-only mounting.
So could not be (for example sr.c) driver extended to directly do pktcdvd's work? So when somebody opens /dev/cdrom device in O_RDWR mode and CD-RW medium is present then it would behave like pktcdvd device... To have /dev/cdrom generic also for CD-RW write access.
> > The removal seems to revert cleanly, although it does require > > reverting a few subsequent commits too (that removed code that only > > pktcdvd used): > > > > git revert db1c7d779767 85d6ce58e493 f40eb99897af > > > > where we have > > > > db1c7d779767 block: bio_copy_data_iter > > 85d6ce58e493 block: remove devnode callback from struct > > block_device_operations > > f40eb99897af pktcdvd: remove driver. > > I'll queue this up - and unless I hear valid complaints to why we should > not just reinstate the driver for now, it'll go out with the next pull > request. > > -- > Jens Axboe >
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