On 05.12.2015 19:12, Daniel Vetter wrote: > On Fri, Dec 04, 2015 at 05:43:33PM -0500, Ilia Mirkin wrote: >> On Fri, Dec 4, 2015 at 5:05 PM, Russell King - ARM Linux >> <linux@xxxxxxxxxxxxxxxx> wrote: >>> On Fri, Dec 04, 2015 at 03:42:47PM -0500, Ilia Mirkin wrote: >>>> On Fri, Dec 4, 2015 at 3:31 PM, Russell King - ARM Linux >>>> <linux@xxxxxxxxxxxxxxxx> wrote: >>>>> Moreover, DRI3 is not yet available for Gallium, so if we're talking >>>>> about Xorg, then functional DRI2 is a requirement, and that _needs_ >>>>> to have a single device for the rendering instances. Xorg has no way >>>>> to pass multiple render nodes to client over DRI2. >>>> >>>> Just to correct... DRI3 has been available on gallium [at least in the >>>> context of st/mesa] basically since DRI3 was introduced. Not sure what >>>> issue you're fighting with, but it's definitely not a gallium >>>> limitation... could be something related to platform devices. >>> >>> Well, my statement is based on the fact that there's nothing in >>> src/gallium/state-tracker/dri which hints at being DRI3. Maybe it's >>> implemented differently, I don't know. The DRI state tracker code in src/gallium/state_trackers/dri/ supports DRI1-3. There's almost no explicit mention of DRI3 in it because DRI3 and DRI2 work mostly the same as far as this code is concerned. >>> I think it's a DRI3 limitation. The issue with the DRI3 design is that: >>> >>> * The client has access to the GPU render nodes only, but not the >>> corresponding KMS node. >>> * Buffers in DRI3 are allocated from the GPU render nodes. >>> * The Xorg Present protocol is then used to manage the vblank >>> synchonisation and page flips. >>> >>> Now, the KMS scanout hardware typically does not support any kind of >>> scatter-gather: the buffers it has must be contiguous. These can be >>> allocated from the KMS DRM device. >>> >>> However, the DRI3 client has no access to the KMS DRM device to allocate >>> linear buffers from, and GPUs typically don't have dumb buffer support. >>> Hence, the client can't pass a suitable buffer to the present layer. > > Oh right, buffer alloc if you have special constraints won't work with > DRI3 as-is. For that we probably need something like DRI2 for buffer alloc > + Present (like DRI3 does) for flipping them. FWIW, that's basically possible already. E.g. the Gallium nine state tracker can use Present even with DRI2. -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
