[haiku] Re: nv_driver in kernel mode, but media kit not?

  • From: "Axel Dörfler" <axeld@xxxxxxxxxxxxxxxx>
  • To: haiku@xxxxxxxxxxxxx
  • Date: Mon, 26 Jul 2010 10:12:54 +0200

Ingo Weinhold <ingo_weinhold@xxxxxx> wrote:
> On 2010-07-25 at 17:20:55 [+0200], Gerald Zajac <zajacg@xxxxxxxxxxxxx> 
> > wrote:
> > Ingo Weinhold wrote:
> > Most drivers consist of a single module which runs in kernel mode;
> > whereas, video drivers consist of two modules.  One module is the 
> > driver
> > which runs in kernel mode;  whereas, the other module is the 
> > accelerant
> > which runs in user mode and does most of the work of interacting 
> > with
> > the video hardware.
> I actually always wondered why Be went with this split for graphics 
> drivers 
> instead of defining a generic ioctl interface (like they did for 
> multi 
> audio).

Programming the 2D acceleration engine would be much slower when done 
using ioctls.
Also, the framebuffer is conveniently mapped into each userspace 
application, so going through the kernel doesn't really get you 
anything.
All the kernel drivers usually do is to provide access to the mapped 
registers, and the memory management needed by the driver.

Bye,
   Axel.

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