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I made my own DOS implementation (Announce)

posted by tom Homepage, Germany (West), 08.12.2023, 15:52

> > >
> > > Unfortunately it does not support FAT32 :-(
> > FAT32 support is critical, should be added.
> The kernel has a filesystem driver API that is currently read-only. A
> dynamic FAT32 driver would be good for testing the write side of things.
> Ext4 would also be cool.
>
> The kernel has a static driver for FAT12/16 filesystem, and I tried to
> write it so that the static driver can easily be replaced with something
> else.
if you search the FreeDOS kernel for #ifdef FAT32 you should get an idea what to change for FAT32 support. it's surprisingly little differenz.

>
> > Perhaps 4kn support,
> What is that?
 "4k native": drives that present the internal 4k sector size - which is normal in modern disks - as 4K to the external world. Most disks emulate a 512 byte sectorsize, even modern ones.


> > GPT and /
> The kernel itself does not support any partitioning tables at all. It has
> syscalls that are used to mount the filesystems from specific offsets on
> the disk. An external program is used to tell the kernel the correct
> beginning sector of every filesystem. Currently the mounter supports only
> MS-DOS-compatible partitioning.
adding GPT support should be easy. actually GPT partitioning is easier then MBR due to the (slightly complicated) extended partitions.
GPT has only primary partitions.

> I have designed my own partitioning scheme
> that supports unlimited number of partitions, but haven't implemented it
> yet.
 Don't do that. use GPT.

>
> The bootloader tells the kernel the offset of the system partition.
>
> > or exFAT support as well
> Writing your own drivers is a good way to contribute to the project.
 ;-)

>
> >, for > 2 TiB drives. Does this feature mean
> > internal support for your OS goes beyond the LBA48 2 TiB BIOS / LBA
> > limitation:
> I don't understand the question. BIOS int13h extensions use 64-bit indexing
> for sectors. There is no 2 TB limitation.
 AFAIK BIOS int13h extensions are implemented as 48-bit indexing in the year 2023.
48 bit are sufficient for 256 TB. Still far away, but remarkably close compared
to the time when it was presented. at that time, 48 bit and Infinity was almost the same.


Good luck on your project, and thanks for sharing with the community.

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