Date:   Thu, 13 Jul 2017 12:58:16 -0700
From:   Stéphane Marchesin <stephane.marchesin@...il.com>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:     Stéphane Marchesin <marcheu@...omium.org>,
        intel-gfx <intel-gfx@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Michael Davidson <md@...gle.com>,
        Grant Grundler <grundler@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Daniel Vetter <daniel.vetter@...el.com>
Subject: Re: [Intel-gfx] [PATCH RESEND] drm/i915: Fix pipe/transcoder enum mismatches

On Thu, Jul 13, 2017 at 10:42 AM, Ville Syrjälä
<ville.syrjala@...ux.intel.com> wrote:
> On Thu, Jul 13, 2017 at 09:23:11AM -0700, Stéphane Marchesin wrote:
>> On Thu, Jul 13, 2017 at 3:13 AM, Ville Syrjälä
>> <ville.syrjala@...ux.intel.com> wrote:
>> > On Wed, Jul 12, 2017 at 07:28:14PM -0700, Stéphane Marchesin wrote:
>> >> On Fri, May 5, 2017 at 10:40 AM, Ville Syrjälä
>> >> <ville.syrjala@...ux.intel.com> 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.
>> >>
>> >>
>> >> I don't follow -- these functions take an enum transcoder; what's
>> >> wrong about passing what they expect? It seems like what you are
>> >> asking for has nothing to do with the warning here...
>> >
>> > There's a warning? I don't get any.
>>
>> Yup, clang generates a warning.
>>
>> >
>> > Anyways, I just don't see much point in blindly changing the types
>> > because it doesn't actually solve the underlying confusion for human
>> > readers. It might even make it worse, not sure.
>>
>> The function expects type A, you pass type B, how can that ever be the
>> right thing to do?
>
> Because maybe the function should be taking in type B instead.

So, if you think this is wrong, can you fix this warning in a way that
you'd like?

Stéphane

>
> --
> Ville Syrjälä
> Intel OTC
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