linux-kernel - Re: [Intel-gfx] [PATCH RESEND] drm/i915: Fix pipe/transcoder enum mismatches

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Date:   Mon, 8 May 2017 09:21:44 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:     Matthias Kaehlcke <mka@...omium.org>,
        dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Michael Davidson <md@...gle.com>,
        Grant Grundler <grundler@...omium.org>,
        Greg Hackmann <ghackmann@...gle.com>,
        Daniel Vetter <daniel.vetter@...el.com>
Subject: Re: [Intel-gfx] [PATCH RESEND] drm/i915: Fix pipe/transcoder enum
 mismatches

On Fri, May 05, 2017 at 08:40:43PM +0300, Ville Syrjälä wrote:
> On Fri, May 05, 2017 at 10:26:36AM -0700, Matthias Kaehlcke wrote:
> > El Thu, Apr 20, 2017 at 02:56:05PM -0700 Matthias Kaehlcke ha dit:
> > 
> > > In several instances the driver passes an 'enum pipe' value to a
> > > function expecting an 'enum transcoder' and viceversa. Since PIPE_x and
> > > TRANSCODER_x have the same values this doesn't cause functional
> > > problems. Still it is incorrect and causes clang to generate warnings
> > > like this:
> > > 
> > > drivers/gpu/drm/i915/intel_display.c:1844:34: warning: implicit
> > >   conversion from enumeration type 'enum transcoder' to different
> > >   enumeration type 'enum pipe' [-Wenum-conversion]
> > >     assert_fdi_rx_enabled(dev_priv, TRANSCODER_A);
> > > 
> > > Change the code to pass values of the type expected by the callee.
> > > 
> > > Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> > > ---
> > >  drivers/gpu/drm/i915/intel_display.c | 4 ++--
> > >  drivers/gpu/drm/i915/intel_dp.c      | 6 ++++--
> > >  drivers/gpu/drm/i915/intel_hdmi.c    | 6 ++++--
> > >  drivers/gpu/drm/i915/intel_sdvo.c    | 6 ++++--
> > >  4 files changed, 14 insertions(+), 8 deletions(-)
> > 
> > Ping, any comments on this patch?
> 
> I'm not convinced the patch is making things any better really. To
> fix this really properly, I think we'd need to introduce a new enum 
> pch_transcoder and thus avoid the confusion of which type of
> transcoder we're talking about. Currently most places expect an 
> enum pipe when dealing with PCH transcoders, and enum transcoder
> when dealing with CPU transcoders. But there are some exceptions
> of course.

enum transcoder is wrong for the pch, that enum is only for cpu
transcoders introduced in hsw+. PCH should always use enum pipe.

So a patch to switch the enum to enum pipe for all the pch functions
sounds like the right thing to do here. Plus maybe rename enum transcoder
to enum cpu_transcoder, but that'd be tons of work. A comment instead
might be easier ...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch