Hado Hein writes:
> I want to implement a device interfacing api in /dev that is already
> done in linux.
Bear in mind that the BSD /dev interface does not provide you with
any easy way to keep track of per-open information. Eg, there
is no file_ptr->private_data.
The only easy way to do this is to have a whole slew of minors, allow
only one open per minor, and to lookup your per-open information based
on the minor number.
> So I scanned the docs about i/o kit and kernel for a simple list (or
> sample code) of how to build a kext that provides a devnode _and_ on
> where to implement the api.
>
> I looked over the darwin sources of rs232 and saw how to register the
> devnode but I found nowhere the implementation of
> open,close,read,write,seek somewhere.
>
> Can one please point me to clear docs where I can see how to implement a
> (dummy) /devnode.
Creating /dev nodes and implementing your own open/close/ioctl, etc,
is outside IOKit. See
/System/Library/Frameworks/Kernel.framework/Headers/sys/conf.h and
/System/Library/Frameworks/Kernel.framework/Headers//miscfs/devfs/devfs.h
For a character device, what you do is to fill in a struct cdevsw (call it
my_cdevsw) with your functions, and call cdevsw_add(-1, &my_cdevsw).
Keep track of the return value, that's your major number.
Then you can call special= devfs_make_node(makedev(major, minor), DEVFS_CHAR,
uid, gid, permissions, name_format_string, name_args) for each of
your special files.
When unloading, you call devfs_remove() on all the specials you
created, and then call cdevsw_remove() with your major and a pointer
to your cdevsw.
I came from FreeBSD, so I never needed docs on this. I think this is
the sort of thing where if you don't already know how to use it, they
don't want you to start ;)
Drew
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