linux-kernel - Re: [PATCH v3 1/2] drm: Add DRM_GEM

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Message-ID: <CAF6AEGvB_uRAJG6YW4zFunHfigXLDdGV3R5Vp11vU4D5pzi0eA@mail.gmail.com>
Date:   Fri, 24 Jun 2022 20:32:57 -0700
From:   Rob Clark <robdclark@...il.com>
To:     Rob Clark <robdclark@...il.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Chris Healy <cphealy@...il.com>,
        Rob Clark <robdclark@...omium.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        David Airlie <airlied@...ux.ie>,
        open list <linux-kernel@...r.kernel.org>
Cc:     Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH v3 1/2] drm: Add DRM_GEM_FOPS

On Fri, Jun 24, 2022 at 1:49 PM Daniel Vetter <daniel@...ll.ch> wrote:
>
> On Thu, Jun 09, 2022 at 10:42:11AM -0700, Rob Clark wrote:
> > From: Rob Clark <robdclark@...omium.org>
> >
> > The DEFINE_DRM_GEM_FOPS() helper is a bit limiting if a driver wants to
> > provide additional file ops, like show_fdinfo().
> >
> > v2: Split out DRM_GEM_FOPS instead of making DEFINE_DRM_GEM_FOPS
> >     varardic
> > v3: nits
> >
> > Signed-off-by: Rob Clark <robdclark@...omium.org>
> > Acked-by: Thomas Zimmermann <tzimmermann@...e.de>
>
> We're at three drivers, maybe it'd be better if this is more standardized?
> I feel like we're opening a bit a can of worms here where everyone just
> has some good odl fashioned fun. It's at least much better documented than
> the old property proliferation :-)

yeah, we could have a standardized drm_show_fdinfo() fop plus
drm_driver callback.. at this point the drm core fxn would be rather
boring, ie. only printing dev->driver->name, so I didn't pursue that
approach (yet?).. but perhaps that changes over time.  I think we
chose the right approach here, focusing on the documentation first so
that userspace has a standardized experience.  The kernel side of
things, we are free to refactor at any time ;-)

BR,
-R

> -Daniel
>
> > ---
> >  include/drm/drm_gem.h | 26 ++++++++++++++++++--------
> >  1 file changed, 18 insertions(+), 8 deletions(-)
> >
> > diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> > index 9d7c61a122dc..87cffc9efa85 100644
> > --- a/include/drm/drm_gem.h
> > +++ b/include/drm/drm_gem.h
> > @@ -314,6 +314,23 @@ struct drm_gem_object {
> >       const struct drm_gem_object_funcs *funcs;
> >  };
> >
> > +/**
> > + * DRM_GEM_FOPS - Default drm GEM file operations
> > + *
> > + * This macro provides a shorthand for setting the GEM file ops in the
> > + * &file_operations structure.  If all you need are the default ops, use
> > + * DEFINE_DRM_GEM_FOPS instead.
> > + */
> > +#define DRM_GEM_FOPS \
> > +     .open           = drm_open,\
> > +     .release        = drm_release,\
> > +     .unlocked_ioctl = drm_ioctl,\
> > +     .compat_ioctl   = drm_compat_ioctl,\
> > +     .poll           = drm_poll,\
> > +     .read           = drm_read,\
> > +     .llseek         = noop_llseek,\
> > +     .mmap           = drm_gem_mmap
> > +
> >  /**
> >   * DEFINE_DRM_GEM_FOPS() - macro to generate file operations for GEM drivers
> >   * @name: name for the generated structure
> > @@ -330,14 +347,7 @@ struct drm_gem_object {
> >  #define DEFINE_DRM_GEM_FOPS(name) \
> >       static const struct file_operations name = {\
> >               .owner          = THIS_MODULE,\
> > -             .open           = drm_open,\
> > -             .release        = drm_release,\
> > -             .unlocked_ioctl = drm_ioctl,\
> > -             .compat_ioctl   = drm_compat_ioctl,\
> > -             .poll           = drm_poll,\
> > -             .read           = drm_read,\
> > -             .llseek         = noop_llseek,\
> > -             .mmap           = drm_gem_mmap,\
> > +             DRM_GEM_FOPS,\
> >       }
> >
> >  void drm_gem_object_release(struct drm_gem_object *obj);
> > --
> > 2.36.1
> >
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch