> On Fri, Apr 27, 2001 at 11:43:45AM +0100, Doug Rabson wrote:
> > This is great Alan. When this gets closer to working, I would like to
try it
> > out. I have a few ideas on how to simplify the authentication code in
the
> > drivers. The linux driver relies on being able to track each individual
open
> > call to the driver which isn't the way BSD drivers work so I try to look
up
> > the auth information using the current PID. I recently realised an
> > alternative way of writing drivers in BSD which would make it possible
to
> > track each open call which would make life easier for DRM.
> >
> Definately could use your help when the compilation issues are out of the
way.
>
> One thing though. We use the copy_from_user and copy_to_user in linux, and
> I've noticed you didn't do that in the original BSD drivers. You just
passed
> a pointer. Was there a reason for this ? From what I can see - we should
> be using copyin/copyout ? Is this right (BSD kernel knowledge is very
new!).
I guess we are talking about ioctls. In BSD (and I think in most AT&T
derived unix kernels), the kernel handles the copyin/copyout of ioctl
arguments. It requires that the data direction and size fields of the ioctl
number are correct and it uses that information to copy to/from a kernel
buffer. The driver's ioctl routing is actually passed a pointer to a kernel
buffer, not the user's pointer. Of course, if the structure passed to ioctl
contains pointers to other user data structures, the driver must perform its
own copyin.
It would be pretty easy to do the copy_from_user/copy_to_user for the linux
drivers in common code and I think it would simplify the drivers.
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