+Puneet,+Zel We will get back to you guys with answers soon. On Dec 1, 2014 9:28 AM, "Daniel Vetter" <daniel at ffwll.ch> wrote:
> On Mon, Dec 01, 2014 at 10:01:37AM +0000, Frank Binns wrote: > > Hi, > > > > We are currently in negotiations with one of our customers (Mediatek) on > > a strategy that will allow them to push a DRM modesetting driver into > > the upstream kernel. We are writing to get people's opinions and > > feedback on our proposed approach. > > > > Currently, our driver is structured in such a way that the display > > driver is more tightly integrated with the GPU driver than we would > > like. Although our kernel driver has been shipped with a GPL license for > > a long time, it is not in a form that would be considered acceptable > > upstream. Unfortunately, it is going to be a long process to get this > > part of the driver into a reasonable state. However, in the meantime, we > > don't want to prevent customer portions of the driver from being > > upstreamed. With the work done on recent kernels, and with a willing > > partner in Mediatek, we now think that we can restructure our driver in > > such a way as to allow this to happen. > > > > We see two basic approaches to achieving this: > > 1) Two independent DRM drivers, i.e. modesetting and render node drivers > > 2) A single componentised DRM driver > > > > Our (IMG's) preferred approach is to have a single componentised DRM > > driver. This is due to the following reasons: > > > > - Existing user space is not fully prepared to handle render nodes. > > > > - There is concern that any IMG DRM render node driver will need > > knowledge about multiple SoCs, each one being from a different vendor. > > Would this be deemed acceptable? > > > > - There is a trend, at least for DRM SoC drivers, towards using the > > component interface. Although there appears to be very few (one?) > > examples of GPU component drivers. > > > > To give some high level details on how we expect the componentised DRM > > driver model to work, each vendor (in this case Mediatek) will write > > their own DRM driver (supporting modesetting, dumb buffers, GEM, prime, > > etc) and IMG will provide an almost entirely independent component > > driver that adds in GPU support. Until our GPU driver is in a suitable > > state this will most likely necessitate a small kernel patch to wire up > > support, e.g. GPU specific ioctls. > > > > Cross-device and cross-process memory allocations will be made using the > > DRM driver. In order for this memory to be shared with the GPU component > > driver it will be necessary, at least for the time being, to export it > > via prime and import it via a GPU ioctl. Synchronisation between the > > display and GPU will be performed via reservation objects. > > > > Does this sound like a sane approach? Questions and/or feedback is very > > welcome. > > Rule of thumb is that if it's an externally licensed IP block it should be > a separate driver. Which is the case here. The idea is that the mostly > generic IMG driver could be reused on other platforms that ship the same > IP-block, while linking up with the respective display controller driver. > The end result is 2 drm drivers: > - Display block drm driver which expose KMS objects for modesetting, but > only very basic gem (just enough to allocate dumb framebuffers and > import/export dma-bufs). > - Full-blown gem driver for the img render IP block. > > For an example look at the tegra/nouveau combo which can run on TK1. > > Plugggin in an IMG driver into each display block like it's currently done > with all the armsoc stuff on android is imo completely no-go. > > Note that the component interface is completely irrelevant wrt the > interface you expose to userspace. It's just an driver-internal helper > library useful in certain situation. Not even the drm core really cares > whether you use component helpers or not. > > Thanks, Daniel > -- > Daniel Vetter > Software Engineer, Intel Corporation > +41 (0) 79 365 57 48 - http://blog.ffwll.ch > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.freedesktop.org/archives/dri-devel/attachments/20141201/57b1e1c6/attachment-0001.html>
