linux-kernel - Re: [Intel-gfx] [PATCH 2/2] drm/dp: Drop open-coded drm_dp_is_branch() in drm_dp_read_downstream_info()

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Date:   Fri, 07 May 2021 17:28:03 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:     intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        open list <linux-kernel@...r.kernel.org>,
        Maxime Ripard <mripard@...nel.org>
Subject: Re: [Intel-gfx] [PATCH 2/2] drm/dp: Drop open-coded
 drm_dp_is_branch() in drm_dp_read_downstream_info()

On Mon, 2021-05-03 at 06:06 +0300, Ville Syrjälä wrote:
> On Fri, Apr 30, 2021 at 06:34:28PM -0400, Lyude Paul wrote:
> > Noticed this while fixing another issue in drm_dp_read_downstream_info(),
> > the open coded DP_DOWNSTREAMPORT_PRESENT check here just duplicates what
> > we
> > already do in drm_dp_is_branch(), so just get rid of it.
> > 
> > Signed-off-by: Lyude Paul <lyude@...hat.com>
> > ---
> >  drivers/gpu/drm/drm_dp_helper.c | 4 +---
> >  1 file changed, 1 insertion(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_dp_helper.c
> > b/drivers/gpu/drm/drm_dp_helper.c
> > index 27c8c5bdf7d9..0f84df8798ab 100644
> > --- a/drivers/gpu/drm/drm_dp_helper.c
> > +++ b/drivers/gpu/drm/drm_dp_helper.c
> > @@ -677,9 +677,7 @@ int drm_dp_read_downstream_info(struct drm_dp_aux
> > *aux,
> >         memset(downstream_ports, 0, DP_MAX_DOWNSTREAM_PORTS);
> >  
> >         /* No downstream info to read */
> > -       if (!drm_dp_is_branch(dpcd) ||
> > -           dpcd[DP_DPCD_REV] < DP_DPCD_REV_10 ||
> > -           !(dpcd[DP_DOWNSTREAMPORT_PRESENT] & DP_DWN_STRM_PORT_PRESENT))
> > +       if (!drm_dp_is_branch(dpcd) || dpcd[DP_DPCD_REV] < DP_DPCD_REV_10)
> 
> BTW that DPCD_REV check looks rather wrong.
> 
> Reviewed-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>

I'll send out a separate fix for this in just a moment, thanks for pointing it
out!

> 
> >                 return 0;
> >  
> >         /* Some branches advertise having 0 downstream ports, despite also
> > advertising they have a
> > -- 
> > 2.30.2
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@...ts.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat

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