NetBSD gains support for the Atari partition scheme

[dressupgeekout]

TL;DR I can transfer files to and from my UltraSatan's SD card even though the disk is NOT formatted with an ordinary MBR.

Hey gang! So, I'm a NetBSD developer. The other day, I was able to extend NetBSD's dk(4) driver to be able to recognize the old, plain TOS hard disk partition map. This allows me to mount the SD card from my UltraSatan, which was formatted with the ICD Pro driver, on a modern PC.

I made a video that explains it all, and you'll get to see a quick demo, too! The code is not committed to NetBSD just yet (pending some code review). If I stare at the code really hard then I *might* be able to get it working in Linux as well.

 

 

[Chri O.]

Sounds pretty cool I am however happy with my homemade hard drive solution with Media Transfer Protocol.

Yet another HD ACSI implementation with Media Transfer Protocol (WIP-Work in progress) ):

Edited February 29 by Chri O.

[theboyfromanotherplanet]

This is pretty cool. A LOT of people have missed TOS support in Linux

[mikro]

Nice! Btw Linux did contain similar code but it is (AFAIK) either disabled or not longer working in recent kernels. So if you could improve that as well, that would be awesome!

[theboyfromanotherplanet]

8 hours ago, mikro said:

Nice! Btw Linux did contain similar code but it is (AFAIK) either disabled or not longer working in recent kernels. So if you could improve that as well, that would be awesome!

AFAIK, it was removed as the filesystems used by AWS/Cloud distros were being misidentified as TOS. Something like that :-)

[dressupgeekout]

So I actually just went ahead and plugged the SD card into my Linux laptop (Debian/x86_64 "bullseye") and the 2 partitions showed up as /dev/mmcblk0p1 and /dev/mmcblk0p2, it Just Worked. That's Linux 5.10, though. Linux 6.8 is A Thing now so maybe something's happened in the meantime that broke support for it. I'd need to dig through the Git history.

 

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/block/partitions/atari.c

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/block/partitions/atari.h/

 

I have a theory. There unfortunately aren't any unique magic numbers to be found inside the TOS partition scheme, AFAICT. This means when the kernel is trying to determine "does this block device represent a TOS-formatted hard disk?" you can't give a definitive y/n answer, you kinda have to guess. My NetBSD code does this, even. If TOS support is removed like you've mentioned, then  my hunch is that the current code is prone to mis-identifying some non-Atari devices to be inappropriately identified as Atari, and the simplest fix is to just never consider TOS partitions altogether.

Edited March 1 by dressupgeekout

[dressupgeekout]

Just wanted to mention that this finally landed in the NetBSD source tree. It works as long as the partition type is GEM or BGM. "Extended" partitions (type "XGM") are not currently supported just yet, I'll try to add that later. https://mail-index.netbsd.org/source-changes/2024/04/02/msg150650.html

[Zap!]

My Ultrasatan's SD cards work fine in my PC, but I'm using PP's HD driver. Well worth the money (under $15 if I remember right).