[openbeos] Re: DiskSetup

On 2005-02-27 at 13:32:33 [+0100], Axel Dörfler wrote:
> Daniel Furrer <daniel_furrer@xxxxxx> wrote:

Mmh, I didn't get the original mail.

> > I just had a quick look at the DiskSetup. It seems like it is one of
> > the
> > few preference apps that are still very much in the first
> > stages of development. Anyway, I was wondering how the DiskSetup is
> > supposed to get its information about the disks&partitions.
> > I didn't find any public API calls that would allow for an easy way
> > to
> > interact with these things - but there seem to be some classes
> > that could help in the (private part? of the) storage kit.
> > Could anyone explain a bit how this is supposed to work?

In BeOS recognition of the boot partition is built into the kernel 
(respectively boot loader), while everything else is done via DriveSetup 
add-ons in userland. Besides DriveSetup those add-ons are also used by 
mountvolume and by a private API (DeviceMap), which the Tracker uses. The 
add-ons implement an interface for scanning/identifying partitions and 
provide a GUI for manipulating partitions (the one you see in DriveSetup).

Our approach to dealing with partitions is quite different from Be's. It is 
kernel-based and generic. Kernel-based means, that besides file system 
kernel modules we also have partitioning system modules and a kernel 
subsystem, the DiskDeviceManager (DDM), that implements all operations on 
partitions (using the file/partitioning system modules to perform specific 
tasks). The functionality is exported to the userland via syscalls and a 
thin C++ API (thin in that method implementations often don't do more than 
invoke a respective syscall; it's very feature-complete though) is provided 
(see headers/private/storage/Disk*.h).

The center of this DiskDevice API is the BDiskDeviceRoster class. It can be 
used to iterate through all installed disk devices (HD, floppy, CD, etc.) 
and the partitions they contain, as well as through all known disk systems 
(i.e. file/partitioning systems). The BPartition class exposes most of the 
manipulation features (creation, moving, resizing, formatting).

Our approach is generic in that you can use this API to manipulate 
partitions without actually knowing anything about their type and contents. 
Nevertheless it is possible to change disk system specific parameters, too. 
A set of userland add-ons (also accessible through the BDiskDeviceRoster) 
will allow anyone to provide a GUI for editing those parameters.

> I think there is little point in recreating DriveSetup as is and at
> this point:
> 1) we have a completely different API than BeOS had (Be's was never
> made public anyway)
> 2) our userland disk device API doesn't work yet IIRC (kernel one does,
> though)

In fact the userland API is virtually completely implemented (save the 
add-on part for edition disk system parameters). Still missing is the write 
and notification support in the kernel, though.

> 3) as our API is a lot more mature and powerful than Be's was, the
> future DriveSetup has a lot more things it can do, and thus, I would
> like to see a new GUI as well
> 4) IIRC Stephan Assmus volunteered more or less officially and
> willingly to do this. Dunno if he's still up to it, though

Well, actually more unofficially. :-)
Anyway things are not really in shape to develop and test something yet. 
That is one could write and build (due to the complete userland API), but 
testing is not really possible.

CU, Ingo

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