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List:       dri-devel
Subject:    Re: [Dri-devel] Re: [Dri-patches] CVS Update: xc (branch: bsd-2-0-0-branch)
From:       Alan Hourihane <ahourihane () valinux ! com>
Date:       2001-04-27 11:10:23
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On Fri, Apr 27, 2001 at 12:06:51PM +0100, Doug Rabson wrote:
> > 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.
> 
Sure. Thanks for that.

Alan.

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