Re: Intel GPU driver import

on 13/05/2012 00:39 Konstantin Belousov said the following:
> With r235375, all required VM support for new Intel GPU driver was
> committed into HEAD. There are still some things to improve and
> change, but now the all.14.9.patch does not touch anything outside agp
> or drm.  This allows to start the process of importing the new Intel
> GPU driver into HEAD.
> 
> I am writing this as initial head-up and to discuss some questions,
> for which I do have answers but would prefer to have additional
> feedback from people doing Xorg work.
> 
> The patch as-is just replaces the Intel DRI1 bits with DRI2
> driver. Patch added most of the KMS infrastructure into DRM
> core. Also, patch completely changed the locking model used by Intel
> driver. I made absolutely minimal efforts needed to keep other DRI1
> drivers compilable. Despite that, I got several surpising reports that
> Radeon DRI1 still works.
> 
> That said, for import I can (first choice) just apply the patch,
> replacing the Intel driver with new one. Or (second choice) I may
> create another directory, say sys/dev/drm2, and import _only_ Intel
> driver together with updated DRM core, there.
> 
> The positive points to the second approach is that we still have older
> kernel drivers around. Also, I have more freedom in changing the DRM
> core, without fearing breakage in the DRI1 land. Since I do not really
> want to deal with Gen2-3 hardware, and VGA console does not work with
> new driver (yet), there are definite advantages.
> 
> On the other hand, driver automatic loading will not work with
> dev/drm2 approach. New driver have to use different module name to
> co-exist with dri1 driver, so ddx driver cannot load new driver by old
> name. As result, users need to manually kldload new driver before
> starting Xorg.
> 
> My own preference is to implement second choice and put the driver
> into dev/drm2.


I think that I would prefer this path too for the reasons you already mentioned above:
- potential problems for other drivers
- need to easily fallback for those who use the intel driver and may run into
problems with the new code
- some missing bits related to kms like syscons support, which makes
troubleshooting harder

BTW, I think that we should patch xf86-video-intel port to try loading
"i915kms"/"i915gem"/... if i915 is not available.  I think that that should be
fine for a FreeBSD-specific patch.
Alternatively, we could keep the same names for drivers/modules and then have a
global knob (WITH_DRM2/WITH_KMS/etc) to select which source is code is used to
build the drivers.

Finally, thank you very much for this work!  Looking forward to having it in the tree.
-- 
Andriy Gapon