Re: [PATCH] drm: drm_gem.h: Add explicit includes for DEFINE_DRM_GEM_FOPS

[Jeffrey Hugo]

On 5/4/2022 3:38 AM, Daniel Vetter wrote:
> On Mon, May 02, 2022 at 06:41:39PM +0300, Jani Nikula wrote:
> > On Fri, 29 Apr 2022, Jeffrey Hugo <quic_jhugo@xxxxxxxxxxx> wrote:
> > > DEFINE_DRM_GEM_FOPS() references drm functions from other headers.  For
> > > example drm_open() is defined in drm_file.h and drm_ioctl() is defined
> > > in drm_ioctl.h.  Since drm_gem.h doesn't include these headers, it
> > > relies on an implicit include from the .c file to have included these
> > > required headers before DEFINE_DRM_GEM_FOPS() gets used.  Relying on
> > > these implicit includes can cause build failures for new code that
> > > doesn't know about these requirements, and can lead to future problems
> > > if the headers ever get restructured as there will be a need to update
> > > every downstream file that includes drm_gem.h.
> > >
> > > Lets fix this explicitly including the required headers in drm_gem.h so
> > > that code that includes drm_gem.h does not need to worry about these
> > > implicit dependencies.
> >
> > In the general case, I tend to agree, but in this specific instance I
> > think I'd err on the side of fewer includes. I think the more likely
> > outcome here is accumulating implicit dependencies on symbols from
> > drm_file.h and drm_ioctl.h by including drm_gem.h only!
> >
> > I do think headers need to be self-contained, and we actually enforce
> > this in i915 (see HDRTEST in drivers/gpu/drm/i915/Makefile), but not to
> > the point of macro expansions.
>
> Yeah we abuse macros in a bunch of places to untangle header dependencies,
> so then going back and pulling in all the headers back in feels a bit
> silly and defeats the point.

Fair enough.  I'll consider this NAK'd

I've been pondering alternate solutions, but haven't come up with any. 
I guess, for now, the status quo will remain.

> iow, I concur.
> -Daniel
>
> > BR,
> > Jani.
> >
> >
> >
> > > Signed-off-by: Jeffrey Hugo <quic_jhugo@xxxxxxxxxxx>
> > > ---
> > >   include/drm/drm_gem.h | 2 ++
> > >   1 file changed, 2 insertions(+)
> > >
> > > diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> > > index 9d7c61a..1cbe3d8 100644
> > > --- a/include/drm/drm_gem.h
> > > +++ b/include/drm/drm_gem.h
> > > @@ -37,6 +37,8 @@
> > >   #include <linux/kref.h>
> > >   #include <linux/dma-resv.h>
> > >   
> > > +#include <drm/drm_file.h>
> > > +#include <drm/drm_ioctl.h>
> > >   #include <drm/drm_vma_manager.h>
> > >   
> > >   struct iosys_map;
> >
> > --
> > Jani Nikula, Intel Open Source Graphics Center