Quoting Tvrtko Ursulin (2018-01-24 12:03:46) > > On 23/01/2018 14:17, Lionel Landwerlin wrote: > > Hi all, > > > > I've been trying to expose some information to userspace about the fused > > parts of the GPU. > > This is the 4th attempt at getting this upstream, here are the previous > > ones : > > https://patchwork.freedesktop.org/patch/185959/ > > https://patchwork.freedesktop.org/series/33436/ > > https://patchwork.freedesktop.org/series/33950/ > > > > This last iteration was based upon some direction by Daniel : > > https://lists.freedesktop.org/archives/dri-devel/2017-December/160162.html > > There was, I think, a fair point about having this working in > > environments where sysfs (mechanism used in the 3rd iteration) is not > > available (containers). > > > > Following some discussion on IRC, it seems Joonas would like this > > rewritten in a such way that we essentially drop the generic mechanism > > introduced in this patch, and instead go for an additional ioctl() on > > the drm fd just for querying the state of a fused part of > > slice/subslice/eus. > > The proposal is to have a single struct like : > > > > struct drm_i915_topology { > > /* All field are in/out */ > > int slice; > > int subslice; > > int eu; > > > > int enabled; > > }; > > > > You would let the slice field to -1 and then the kernel would fill it > > with the max slice value. Same for subslice (with a valid slice value) > > and eu. > > When querying with slice = 0, and all other fields to -1, the kernel > > would fill the enabled value with 0 or 1. > > Essentially that would mean that an application wanting to query the > > state of all of the EUs would have to go through them one by one (which > > would be about ~100 ioctl() on SKL GT4 for example). > > > > Apart from the fact that we'll probably end up adding another ioctl() > > for engine discovery, I don't have any problem with what Joonas is > > proposing. > > It's just a bit annoying this comes up on the 4th rewrite. > > I really wouldn't like to rewrite this one more time and get turned down > > because this isn't to the taste of one of the reviewer. > > So my question is : Is everybody happy with what Joonas is proposing? > > Anybody in favor of having a generic mechanism? > > I am not very keen on this counter-proposal for two reasons. > > First is that I think is a bit inelegant to have to query so many times > just to get the full topology out. If this ends in some library, we may > end up running this on every trivial client startup. > > Secondly, it is kind of dispatcher in it's own right. Since the > operation mode will depend on the combination of field values. As such a > generic, or at least a more explicit, dispatcher, like the proposed > i915_query_ioctl sounds cleaner to me. > > I take the point we can't guess how many other users we will have for it > in the future. So there is a little bit of a risk of adding something > generic which won't be used a lot in the future. > > Because apart from the three queries Lionel needs, I would be adding an > engine info query and potentially, depending on userspace interest, > engine queue depths. So that would be a maximum of five queries I am > aware of would use the generic framework. Maybe too little, or maybe > good enough for a start?
Another use case would be a single shot method to gather all GETPARAMs. There's a lot of too'ing and fro'ing at the start of mesa trying to determine all of the kernel's capabilities, which more or less come down to a long series of parsing GETPARAM results. Bundling all of those up into a single ioctl seems attractive to me (bonus for it being properly defined and not a compat nightmare). -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
