why drm?

Andrea Venturoli ml at netfence.it
Tue Feb 19 16:22:02 UTC 2013

On 02/19/13 09:22, Anton Shterenlikht wrote:
> I'm confused about DRM/DRI.

Hi Anton.
I waited before replying, since I'm no expert on this one; in fact I 
share some of your doubts.
However, since no one else stepped forward, I'll try what little I can.

> I've done some brief reading but still
> not clear what these do, or
> even if DRM and DRI do the same thing?

Take a look at this:

I cannot verify if this is current or even correct, but there are some 
sentences which might answer you:

"The Direct Rendering Manager, DRM, is the kernel part of the wider 
Direct Rendering Infrastructure (DRI)."...
"With DRM in place, the X server uses the ioctl interface to pass its 
commands down to the kernel."...
""DRI" could be taken to mean the overall infrastructure which makes 
accelerated rendering possible.  The DRI interface, which is what this 
section is about, is specific to X."...
"DRI is just one way to use the underlying DRM framework.  For instance, 
there are other graphics systems (such as Wayland) which also use DRM to 
access the hardware."

> If I build a kernel with drm:
> # grep drm /root/kernels/BUZI
> device          drm             # DRM core module required by DRM drivers
> device          i915drm         # Intel i830 through i915
> device          r128drm         # ATI Rage 128
> device          radeondrm       # ATI Radeon
> device          viadrm          # VIA
> #
> (I probably don't need all these drm options)

I have a Radeon too, although not the same model you have.
I never compiled drm modules into the kernel, they get loaded dynamically.

> 1. Do I need DRM/DRI. My understanding is
> that X will do just as well without it,
> perhaps a bit slower. Is that correct?

I'm not sure you can run the Radeon driver without drm and radeon 
modules; for sure you don't need them in the kernel.
You could also try the VESA driver if speed is not an issue.

Do you have a xorg.conf file? If so, what's in Section "Module"?

> I'd be grateful for any advice or a link
> to a relevant existing document.

Unfortunately, with recent X, I always found it hard to find documents 
which could stay "current" for a long time.



So that other might help you, it would possibly be useful to know which 
version of FreeBSD you are running.

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