On Mon, Sep 28, 2015 at 01:52:31PM -0700, Bernie Thompson wrote: > On Sat, Sep 26, 2015 at 11:01 AM, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> > wrote: > > The smallest of these (udl) still counts in at ca. 2800 LoC, > > Note udlfb.c, the original fbdev driver that I helped write and that the > udl DRM driver was based on, is ~1800 LoC ... so we're actually talking in > the ballpark of 2x (rather than 10x) between fbdev and DRM in this case. > That said, the complexity difference is probably higher than the LoC > difference. I know I personally have struggled in the shift from > understanding fbdev to understanding DRM. udl has a bit of room for improvement, we really should push the worker logicy for fbdev emulation into the core drm fbdev helpers using the ->dirtyfb callback. That should rip out quite a few lines. The other thing to consider is that drm/udl supports PRIME buffer sharing for seamlessly extending your desktop by just plugging in an usb dongle. > The fact that there's drivers of both types and USB hardware might make udl > may be a good driver to use as a base for any additional simplification / > helper work. David Airlie and David Herrmann both have this hardware. David > Airlie did the port from fbdev to DRM, so he's made it an exemplary > driver. And if anyone needs any hardware which works with udlfb and udl, > we're happy to send free hardware to any programmers who are willing to > contribute in the form of code or testing: > http://plugable.com/projects/plugable-open-source-hardware-samples-program For example drivers I think it's better to look at the latest drm driver merged - those are up-to-date wrt best practices. udl has already accumulated a bit of cruft (e.g. still using legacy modeset helpers and not the atomic ones). > More simplification and documentation would be great. In particular, the > optimization for the connector+encoder+crtc combination others have > mentioned seems like it would be worthwhile. Atomic helpers already make almost everything optional except for the crtc-level enable/disable callbacks and the per-plane atomic_plane_update (for buffer flips/panning/rotation/...). So a comibined helper would be mostly for cutting down the structure setup/teardown boilerplate. So should be fairly easy to implement even for drm beginners (when using one of the latest drivers as a template for what needs to be done). -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
