Re: [PATCH v3 8/9] dma-buf/sync_file: Add SET_DEADLINE ioctl

[Rob Clark]

On Wed, Sep 8, 2021 at 11:49 AM Daniel Vetter <daniel@xxxxxxxx> wrote:
>
> On Wed, Sep 08, 2021 at 11:23:42AM -0700, Rob Clark wrote:
> > On Wed, Sep 8, 2021 at 10:50 AM Daniel Vetter <daniel@xxxxxxxx> wrote:
> > >
> > > On Fri, Sep 03, 2021 at 11:47:59AM -0700, Rob Clark wrote:
> > > > From: Rob Clark <robdclark@xxxxxxxxxxxx>
> > > >
> > > > The initial purpose is for igt tests, but this would also be useful for
> > > > compositors that wait until close to vblank deadline to make decisions
> > > > about which frame to show.
> > > >
> > > > Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> > >
> > > Needs userspace and I think ideally also some igts to make sure it works
> > > and doesn't go boom.
> >
> > See cover-letter.. there are igt tests, although currently that is the
> > only user.
>
> Ah sorry missed that. It would be good to record that in the commit too
> that adds the uapi. git blame doesn't find cover letters at all, unlike on
> gitlab where you get the MR request with everything.
>
> Ok there is the Link: thing, but since that only points at the last
> version all the interesting discussion is still usually lost, so I tend to
> not bother looking there.
>
> > I'd be ok to otherwise initially restrict this and the sw_sync UABI
> > (CAP_SYS_ADMIN?  Or??) until there is a non-igt user, but they are
> > both needed by the igt tests
>
> Hm really awkward, uapi for igts in cross vendor stuff like this isn't
> great. I think hiding it in vgem is semi-ok (we have fences there
> already). But it's all a bit silly ...
>
> For the tests, should we instead have a selftest/Kunit thing to exercise
> this stuff? igt probably not quite the right thing. Or combine with a page
> flip if you want to test msm.

Hmm, IIRC we have used CONFIG_BROKEN or something along those lines
for UABI in other places where we weren't willing to commit to yet?

I suppose if we had to I could make this a sw_sync ioctl instead.  But
OTOH there are kind of a limited # of ways this ioctl could look.  And
we already know that at least some wayland compositors are going to
want this.

I guess I can look at non-igt options.  But the igt test is already a
pretty convenient way to contrive situations (like loops, which is a
thing I need to add)

BR,
-R


> -Daniel
>
> >
> > BR,
> > -R
> >
> > > -Daniel
> > >
> > > > ---
> > > >  drivers/dma-buf/sync_file.c    | 19 +++++++++++++++++++
> > > >  include/uapi/linux/sync_file.h | 20 ++++++++++++++++++++
> > > >  2 files changed, 39 insertions(+)
> > > >
> > > > diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
> > > > index 394e6e1e9686..f295772d5169 100644
> > > > --- a/drivers/dma-buf/sync_file.c
> > > > +++ b/drivers/dma-buf/sync_file.c
> > > > @@ -459,6 +459,22 @@ static long sync_file_ioctl_fence_info(struct sync_file *sync_file,
> > > >       return ret;
> > > >  }
> > > >
> > > > +static int sync_file_ioctl_set_deadline(struct sync_file *sync_file,
> > > > +                                     unsigned long arg)
> > > > +{
> > > > +     struct sync_set_deadline ts;
> > > > +
> > > > +     if (copy_from_user(&ts, (void __user *)arg, sizeof(ts)))
> > > > +             return -EFAULT;
> > > > +
> > > > +     if (ts.pad)
> > > > +             return -EINVAL;
> > > > +
> > > > +     dma_fence_set_deadline(sync_file->fence, ktime_set(ts.tv_sec, ts.tv_nsec));
> > > > +
> > > > +     return 0;
> > > > +}
> > > > +
> > > >  static long sync_file_ioctl(struct file *file, unsigned int cmd,
> > > >                           unsigned long arg)
> > > >  {
> > > > @@ -471,6 +487,9 @@ static long sync_file_ioctl(struct file *file, unsigned int cmd,
> > > >       case SYNC_IOC_FILE_INFO:
> > > >               return sync_file_ioctl_fence_info(sync_file, arg);
> > > >
> > > > +     case SYNC_IOC_SET_DEADLINE:
> > > > +             return sync_file_ioctl_set_deadline(sync_file, arg);
> > > > +
> > > >       default:
> > > >               return -ENOTTY;
> > > >       }
> > > > diff --git a/include/uapi/linux/sync_file.h b/include/uapi/linux/sync_file.h
> > > > index ee2dcfb3d660..f67d4ffe7566 100644
> > > > --- a/include/uapi/linux/sync_file.h
> > > > +++ b/include/uapi/linux/sync_file.h
> > > > @@ -67,6 +67,18 @@ struct sync_file_info {
> > > >       __u64   sync_fence_info;
> > > >  };
> > > >
> > > > +/**
> > > > + * struct sync_set_deadline - set a deadline on a fence
> > > > + * @tv_sec:  seconds elapsed since epoch
> > > > + * @tv_nsec: nanoseconds elapsed since the time given by the tv_sec
> > > > + * @pad:     must be zero
> > > > + */
> > > > +struct sync_set_deadline {
> > > > +     __s64   tv_sec;
> > > > +     __s32   tv_nsec;
> > > > +     __u32   pad;
> > > > +};
> > > > +
> > > >  #define SYNC_IOC_MAGIC               '>'
> > > >
> > > >  /**
> > > > @@ -95,4 +107,12 @@ struct sync_file_info {
> > > >   */
> > > >  #define SYNC_IOC_FILE_INFO   _IOWR(SYNC_IOC_MAGIC, 4, struct sync_file_info)
> > > >
> > > > +
> > > > +/**
> > > > + * DOC: SYNC_IOC_SET_DEADLINE - set a deadline on a fence
> > > > + *
> > > > + * Allows userspace to set a deadline on a fence, see dma_fence_set_deadline()
> > > > + */
> > > > +#define SYNC_IOC_SET_DEADLINE        _IOW(SYNC_IOC_MAGIC, 5, struct sync_set_deadline)
> > > > +
> > > >  #endif /* _UAPI_LINUX_SYNC_H */
> > > > --
> > > > 2.31.1
> > > >
> > >
> > > --
> > > Daniel Vetter
> > > Software Engineer, Intel Corporation
> > > http://blog.ffwll.ch
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch