linux-kernel - Re: [PATCH 1/2] drm/amd/display: change variables type

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Message-ID: <20220727001124.dsulur5hhlinjg6o@mail.igalia.com>
Date:   Tue, 26 Jul 2022 23:11:44 -0100
From:   Melissa Wen <mwen@...lia.com>
To:     Magali Lemes <magalilemes00@...il.com>
Cc:     André Almeida <andrealmeid@...lia.com>,
        siqueirajordao@...eup.net, mairacanal@...eup.net,
        sunpeng.li@....com, tales.aparecida@...il.com, Xinhui.Pan@....com,
        Rodrigo.Siqueira@....com, linux-kernel@...r.kernel.org,
        amd-gfx@...ts.freedesktop.org, airlied@...ux.ie,
        dri-devel@...ts.freedesktop.org, alexander.deucher@....com,
        isabbasso@...eup.net, andrealmeid@...eup.net,
        christian.koenig@....com
Subject: Re: [PATCH 1/2] drm/amd/display: change variables type

On 07/26, Magali Lemes wrote:
> On 7/25/22 20:38, Melissa Wen wrote:
> 
> > On 07/25, Magali Lemes wrote:
> > > On 7/25/22 16:42, André Almeida wrote:
> > > > Hi Magali,
> > > > 
> > > > Às 15:15 de 25/07/22, Magali Lemes escreveu:
> > > > > As "dcn3_15_soc" and "dcn3_16_soc" are of type "struct
> > > > > _vcs_dpi_soc_bounding_box_st", change their types accordingly.
> > > > > 
> > > > I can see that indeed this type change sense for those variables, but
> > > > isn't a bit strange that the type was wrong in the first place? I wonder
> > > > if this variable is even used, given that it would very likely throw a
> > > > compiler error when using the wrong type and trying to access struct
> > > > members that aren't defined.
> > > 
> > > A compilation error would be thrown if either "dc/dcn315/dcn315_resource.h"
> > > or "dc/dcn316/dcn316_resource.h" were included in the files where
> > > "dcn3_15_soc" and "dcn3_16_soc" are initialized. Since they are not
> > > included, the wrong variable type error is not shown.
> > > To solve the sparse warning in the second patch of this series, those
> > > variables need to be declared first, but they are already declared, we're
> > > only missing the headers. If I only add the headers, then those variables
> > > will be seen, and I get the expected incompatible variables types error. So,
> > > fixing the types here is a preliminary work for the next patch.
> > > 
> > Hi Magali,
> > 
> > Thanks for inspecting it. What you say makes sense, but André pointed
> > out something that makes sense to me too.
> > 
> > As fas as I checked, dcn3_15_soc and dcn16_soc is not used outside their
> > respective FPU files. Maybe the proper solution is removing those
> > declarations (and make the struct static). Can you take a look at it?
> > 
> > Best Regards,
> > 
> > Melissa
> 
> Hi, Melissa. Thank you for the suggestion!
> My sole reason not to make those structs static was to keep some sort of
> consistency with the rest of the dcn*_resource.h files, since that is where
> all the other structs are first declared. I'm not sure, though, if that's a
> good enough reason not to turn these variables into static. Let me know what
> you think.

I don't see any other file using dcn3_15_soc, it's only in dcn30_fpu, so
better make it static. Also, I see that doing this will ring a bell
for some misuse of the struct outside FPU protection, in the future.

With those points addressed, you can add in the next version:

Reviewed-by: Melissa Wen <mwen@...lia.com>

Thanks,

Melissa

> 
> Magali
> 
> 
> 
> > Magali
> > 
> > 
> > > > > Signed-off-by: Magali Lemes <magalilemes00@...il.com>
> > > > > ---
> > > > >    drivers/gpu/drm/amd/display/dc/dcn315/dcn315_resource.h | 2 +-
> > > > >    drivers/gpu/drm/amd/display/dc/dcn316/dcn316_resource.h | 2 +-
> > > > >    2 files changed, 2 insertions(+), 2 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/amd/display/dc/dcn315/dcn315_resource.h b/drivers/gpu/drm/amd/display/dc/dcn315/dcn315_resource.h
> > > > > index 39929fa67a51..45276317c057 100644
> > > > > --- a/drivers/gpu/drm/amd/display/dc/dcn315/dcn315_resource.h
> > > > > +++ b/drivers/gpu/drm/amd/display/dc/dcn315/dcn315_resource.h
> > > > > @@ -32,7 +32,7 @@
> > > > >    	container_of(pool, struct dcn315_resource_pool, base)
> > > > >    extern struct _vcs_dpi_ip_params_st dcn3_15_ip;
> > > > > -extern struct _vcs_dpi_ip_params_st dcn3_15_soc;
> > > > > +extern struct _vcs_dpi_soc_bounding_box_st dcn3_15_soc;
> > > > >    struct dcn315_resource_pool {
> > > > >    	struct resource_pool base;
> > > > > diff --git a/drivers/gpu/drm/amd/display/dc/dcn316/dcn316_resource.h b/drivers/gpu/drm/amd/display/dc/dcn316/dcn316_resource.h
> > > > > index 0dc5a6c13ae7..d2234aac5449 100644
> > > > > --- a/drivers/gpu/drm/amd/display/dc/dcn316/dcn316_resource.h
> > > > > +++ b/drivers/gpu/drm/amd/display/dc/dcn316/dcn316_resource.h
> > > > > @@ -32,7 +32,7 @@
> > > > >    	container_of(pool, struct dcn316_resource_pool, base)
> > > > >    extern struct _vcs_dpi_ip_params_st dcn3_16_ip;
> > > > > -extern struct _vcs_dpi_ip_params_st dcn3_16_soc;
> > > > > +extern struct _vcs_dpi_soc_bounding_box_st dcn3_16_soc;
> > > > >    struct dcn316_resource_pool {
> > > > >    	struct resource_pool base;


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