Re: [RFC 4/4] drm: Add NVIDIA Tegra support

On Wed, Apr 11, 2012 at 03:23:26PM +0200, Thierry Reding wrote:

* Daniel Vetter wrote:

quoted

On Wed, Apr 11, 2012 at 02:10:30PM +0200, Thierry Reding wrote:

quoted

This commit adds a very basic DRM driver for NVIDIA Tegra SoCs. It
currently has rudimentary GEM support and can run a console on the
framebuffer as well as X using the xf86-video-modesetting driver.
Only the RGB output is supported. Quite a lot of things still need
to be worked out and there is a lot of room for cleanup.

Indeed, after a quick look there are tons of functions that are just stubs
;-) One thing I wonder though is why you directly use the iommu api and
not wrap it up into dma_map? Is arm infrastructure just not there yet or
do you plan to tightly integrate the tegra drm with the iommu (e.g. for
process space switching or similarly funky stuff)?

I'm not sure I know what you are referring to. Looking for all users of
iommu_map() doesn't turn up anything related to dma_map. Can you point me in
the right direction?

Well, you use the iommu api to map/unmap memory into the iommu for tegra,
whereas usually device drivers just use the dma api to do that. The usual
interface is dma_map_sg/dma_unmap_sg, but there are quite a few variants
around. I'm just wondering why this you've choosen this.
-Daniel
-- 
Daniel Vetter
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