Hi David, On Wednesday 29 Mar 2017 14:51:48 David Herrmann wrote: > On Wed, Mar 29, 2017 at 2:20 PM, Laurent Pinchart wrote: > > On Wednesday 29 Mar 2017 11:58:23 Tomi Valkeinen wrote: > >> On 29/03/17 11:22, Laurent Pinchart wrote: > >>> On Tuesday 28 Mar 2017 16:07:52 Tomi Valkeinen wrote: > >>>> From: Hemant Hariyani <hemanthariyani@xxxxxx> > >>>> > >>>> Add support for render nodes in omap driver and allow required > >>>> ioctls to be accessible via render nodes. > >>> > >>> But the OMAP DSS doesn't perform rendering... This seems an abuse of > >>> render nodes, I think the API should instead be implemented by the GPU > >>> driver. > >> > >> I agree that the GPU use case described in the patch sounds a bit odd. > >> Why not allocate from the GPU driver instead. But here a particular > >> issue is that to get TILER buffers we need to ask them from the omapdrm. > >> Probably TILER should not be part of omapdrm, but then, where should it > >> be... > >> > >> We also have writeback in DSS, which can function as a memory to memory > >> or capture device. That's not supported in the mainline, but we have > >> support in the TI kernel. > >> > >> And how about a case where you have the privileged process as KMS > >> master, and another process wants to draw to a buffer with the CPU, and > >> then give the buffer to the privileged process for displaying. > >> > >> So, yes, DSS is not a renderer (well, WB is kind of rendering), but > >> isn't it a valid use case to allocate a buffer from omapdrm? > > > > It could be a valid use case, but it's still an API abuse. It starts > > sounding like a DRM core issue to me. The DRIVER_RENDER flag is not > > documented, so its exact meaning isn't defined. I thought it was supposed > > to flag the device as a renderer (GPU). > > > > commit 1793126fcebd7c18834f95d43b55e387a8803aa8 > > Author: David Herrmann <dh.herrmann@xxxxxxxxx> > > Date: Sun Aug 25 18:29:00 2013 +0200 > > > > drm: implement experimental render nodes > > > > Render nodes provide an API for userspace to use non-privileged GPU > > commands without any running DRM-Master. It is useful for offscreen > > rendering, GPGPU clients, and normal render clients which do not > > perform > > modesetting. > > > > [...] > > > > You instead use the flag as a way to enable unprivileged clients to > > allocate buffers. If that's what the flag should mean, I wonder if there > > would be a use case for *not* setting it. > > Correct. You can (and should) enable all your sandboxed commands on > render nodes. That is, if a command only affects the issuing client, > then it is safe for render-nodes. If two clients have a file-context > opened on the render node, they should be unable to affect each other > (minus accounting, resource allocation, etc.). > > The name is historic (I did not come up with it either, but failed at > renaming it..). The DRIVER_RENDER flag only controls whether the > render-node is actually instantiated. I will not object doing that > unconditionally. It will create some useless nodes for legacy drivers, > but we should not care. Couldn't we achieve the same effect without render nodes, by allowing GEM object allocation on the main DRM node by unauthenticated clients ? -- Regards, Laurent Pinchart _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
