linux-kernel - Re: [PATCH v2 3/5] drm/msm/dp: Support up to 3 DP controllers

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Date:   Thu, 26 Aug 2021 09:57:18 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Abhinav Kumar <abhinavk@...eaurora.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Kalyan Thota <kalyan_t@...eaurora.org>,
        Kuogee Hsieh <khsieh@...eaurora.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/5] drm/msm/dp: Support up to 3 DP controllers

On Thu 26 Aug 00:13 PDT 2021, Stephen Boyd wrote:
> Quoting Bjorn Andersson (2021-08-25 16:42:31)
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
[..]
> > @@ -203,8 +204,8 @@ static int dpu_kms_debugfs_init(struct msm_kms *kms, struct drm_minor *minor)
> >         dpu_debugfs_vbif_init(dpu_kms, entry);
> >         dpu_debugfs_core_irq_init(dpu_kms, entry);
> >
> > -       if (priv->dp)
> > -               msm_dp_debugfs_init(priv->dp, minor);
> > +       for (i = 0; i < ARRAY_SIZE(priv->dp); i++)
> > +               msm_dp_debugfs_init(priv->dp[i], minor);
> 
> Does this need the same if (!priv->dp) continue check like the other
> loops over priv->dp?
> 
[..]
> > @@ -800,7 +809,8 @@ static int dpu_irq_postinstall(struct msm_kms *kms)
> >         if (!priv)
> >                 return -EINVAL;
> >
> > -       msm_dp_irq_postinstall(priv->dp);
> > +       for (i = 0; i < ARRAY_SIZE(priv->dp); i++)
> > +               msm_dp_irq_postinstall(priv->dp[i]);
> 
> This one too? Or maybe those gained NULL pointer checks.
> 

This already has a NULL check, that's why I added one to the adjacent
msm_dp_debugfs_init() as well.

> >
> >         return 0;
> >  }
> > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
[..]
> > @@ -1194,6 +1230,10 @@ static int dp_display_probe(struct platform_device *pdev)
> >         if (!dp)
> >                 return -ENOMEM;
> >
> > +       dp->id = dp_display_get_id(pdev);
> 
> Ah ok, it's signed for this error check. Maybe assign dp->id in the
> function and return 0 instead of assigning it here?
> dp_display_assign_id()
> 

I like the fact that the "getter" doesn't have side effects, but making
dp->id unsigned makes sense. So let's pay the price of a local signed
variable here.

> > +       if (dp->id < 0)
> > +               return -EINVAL;
> > +

Thanks for the feedback,
Bjorn