[openbeosstorage] Re: First C Device API Draft
- From: "Ingo Weinhold" <bonefish@xxxxxxxxxxxxxxx>
- To: openbeosstorage@xxxxxxxxxxxxx
- Date: Sun, 29 Dec 2002 01:05:37 CET (+0100)
>
> "Ingo Weinhold" <bonefish@xxxxxxxxxxxxxxx> wrote:
> > I was almost starting to implement it, when I started wondering
> > whether
> > it would be better to return/pass a pointer to the module itself,
> > not
> > just the name. This would even save the overhead for loading/
> > unloading
> > the module each time. Then the caller would be responsible for
> > calling
> > put=5Fmodule() (unless a NULL module=5Finfo** had been supplied or
> > the
> > returned pointer was NULL). How does that sound=3F
>
> Sounds okay, I think... at least it must be documented that you have
> to
> do that :)
That wouldn't be a problem. :-)
> > I'm not longer sure, whether it is possible at all.
> > B=5FGET=5FPARTITION=5FINFO has to be called on the partition
> > device, not on
> > the raw device, and I wouldn't know how to get hold of it (it's in
> > the
> > same dir as the raw device, but that doesn't really help...).
>
> Where is the problem=3F AFAICT the devfs directs all calls to the raw
> device, altering the position and size of the read/write calls,
> answering to ioctl()s the raw device cannot know about, etc.
That's what I think too, but how does it help with getting the name of
the raw device from a file descriptor for it? devfs certainly knows the
name of the raw device belonging to a partition, since it is told so
via B_SET_PARTITION, and can report it on a B_GET_PARTITION_INFO, but
getting a name for a FD is the one thing, that usually doesn't work out
(as with node_refs), unless there is some private magic.
> > OK. But then we should find a way to fill it in for the time being,
> > since one would certainly like to use it in implementation of the C
> > ++
> > API.
>
> The "df" command also lists the mount point of the volumes, should be
> possible, although it obviously uses a private call =5Fkstatfs=5F() :
> -)
That way around, it is easy. You can use next_dev() to iterate through
the mounted volumes and fs_stat_dev() to get information about them
(the mount point among other details), or alternatively BVolume/
BVolumeRoster. Given a device FD and the question, whether and where
that device is mounted, is a bit more difficult. Either an ioctl/
syscall needs to be provided to get that info directly, or one has to
iterate through the mounted devices and check whether the given one is
among them.
CU, Ingo
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