On Thu, Oct 16, 2014 at 01:48:20PM +0300, Jani Nikula wrote: > On Thu, 16 Oct 2014, Daniel Vetter <daniel.vetter@xxxxxxxx> wrote: > > Too many new drm driver writers seem to look at i915 for inspiration. > > But we have two ways to do mmap, so discourage readers from the old, > > ugly version. In a new driver we'd just expose two mmap offsets per > > object, one for the gtt map and the other for the cpu map. > > > > Cc: "Cheng, Yao" <yao.cheng@xxxxxxxxx> > > Cc: David Herrmann <dh.herrmann@xxxxxxxxx> > > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx> > > --- > > drivers/gpu/drm/i915/i915_gem.c | 9 +++++++++ > > 1 file changed, 9 insertions(+) > > > > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c > > index e9c783d55612..09d859b89aac 100644 > > --- a/drivers/gpu/drm/i915/i915_gem.c > > +++ b/drivers/gpu/drm/i915/i915_gem.c > > @@ -1466,6 +1466,15 @@ unlock: > > * > > * While the mapping holds a reference on the contents of the object, it doesn't > > * imply a ref on the object itself. > > + * > > + * IMPORTANT: > > + * > > + * DRM driver writers who look a this function as an example for how to do GEM > > + * mmap support, please don't implement mmap support like here. The modern way > > + * to implement DRM mmap support is with an mmap offset ioctl (like > > + * i915_gem_mmap_gtt) and then using the mmap syscall on the DRM fd directly. > > + * That way debug tooling like valgrind will understand what's going on, hiding > > + * the mmap call in a driver private ioctl will break that. > > Maybe a sentence here about why we're doing things differently, instead > of merely "do as I say, don't do as I do"? It smells like hysterical > raisins, but no harm in spelling it out, right? Ok, I'll add a "The i915 only does mmap this way because we didn't know better". -Daniel > > BR, > Jani. > > > */ > > int > > i915_gem_mmap_ioctl(struct drm_device *dev, void *data, > > -- > > 1.9.3 > > > > _______________________________________________ > > Intel-gfx mailing list > > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx > > http://lists.freedesktop.org/mailman/listinfo/intel-gfx > > -- > Jani Nikula, Intel Open Source Technology Center -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
