Re: [PATCH 02/25] dma-fence: prime lockdep annotations

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Fri, Jul 10, 2020 at 4:23 PM Jason Gunthorpe <jgg@xxxxxxxxxxxx> wrote:
>
> On Fri, Jul 10, 2020 at 04:02:35PM +0200, Daniel Vetter wrote:
>
> > > dma_fence only possibly makes some sense if you intend to expose the
> > > completion outside a single driver.
> > >
> > > The prefered kernel design pattern for this is to connect things with
> > > a function callback.
> > >
> > > So the actual use case of dma_fence is quite narrow and tightly linked
> > > to DRM.
> > >
> > > I don't think we should spread this beyond DRM, I can't see a reason.
> >
> > Yeah v4l has a legit reason to use dma_fence, android wants that
> > there.
>
> 'legit' in the sense the v4l is supposed to trigger stuff in DRM when
> V4L DMA completes? I would still see that as part of DRM

Yes, and also the other way around. But thus far it didn't land.
-Daniel

> Or is it building a parallel DRM like DMA completion graph?
>
> > > Trying to improve performance of limited HW by using sketchy
> > > techniques at the cost of general system stability should be a NAK.
> >
> > Well that's pretty much gpu drivers, all the horrors for a bit more speed :-)
> >
> > On the text itself, should I upgrade to "must not" instead of "should
> > not"? Or more needed?
>
> Fundamentally having some unknowable graph of dependencies where parts
> of the graph can be placed in critical regions like notifiers is a
> complete maintenance nightmare.
>
> I think building systems like this should be discouraged :\

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel



[Index of Archives]     [Linux DRI Users]     [Linux Intel Graphics]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux