linux-kernel - Re: [PATCH] drm/radeon: fix uninitialized bool variable

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Message-ID: <CADnq5_PwkRb=2z2ak5f8gnAwzQLdE_6ACjtNvpe+6hECxxsCpA@mail.gmail.com>
Date:   Mon, 20 Sep 2021 12:00:50 -0400
From:   Alex Deucher <alexdeucher@...il.com>
To:     Christian König <ckoenig.leichtzumerken@...il.com>
Cc:     Zhiwei Yang <yangzhiwei@...ontech.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/radeon: fix uninitialized bool variable

On Mon, Sep 20, 2021 at 3:44 AM Christian König
<ckoenig.leichtzumerken@...il.com> wrote:
>
>
>
> Am 18.09.21 um 11:41 schrieb Zhiwei Yang:
> > The bool variable detected_hpd_without_ddc in struct radeon_connector
> > is uninitialized when first used, that may cause unnecessary ddc ops.
> > Make it as false when a new connector is alloced.
> >
> > Signed-off-by: Zhiwei Yang <yangzhiwei@...ontech.com>
> > ---
> >   drivers/gpu/drm/radeon/radeon_connectors.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/radeon/radeon_connectors.c b/drivers/gpu/drm/radeon/radeon_connectors.c
> > index fe12d9d91d7a..c1987a66373f 100644
> > --- a/drivers/gpu/drm/radeon/radeon_connectors.c
> > +++ b/drivers/gpu/drm/radeon/radeon_connectors.c
> > @@ -1866,6 +1866,7 @@ radeon_add_atom_connector(struct drm_device *dev,
> >       bool shared_ddc = false;
> >       bool is_dp_bridge = false;
> >       bool has_aux = false;
> > +     bool detected_hpd_without_ddc = false;
>
> In general good catch, but I don't see the need for a local variable here.
>
> Just initialize the member directly or even better change the allocation
> of the connector into a kzalloc().

This is already the case:
        radeon_connector = kzalloc(sizeof(struct radeon_connector), GFP_KERNEL);
So I don't think this patch is necessary.

Alex

>
> Christian.
>
> >
> >       if (connector_type == DRM_MODE_CONNECTOR_Unknown)
> >               return;
> > @@ -1923,6 +1924,7 @@ radeon_add_atom_connector(struct drm_device *dev,
> >       radeon_connector->shared_ddc = shared_ddc;
> >       radeon_connector->connector_object_id = connector_object_id;
> >       radeon_connector->hpd = *hpd;
> > +     radeon_connector->detected_hpd_without_ddc = detected_hpd_without_ddc;
> >
> >       radeon_connector->router = *router;
> >       if (router->ddc_valid || router->cd_valid) {
> > @@ -2384,6 +2386,7 @@ radeon_add_legacy_connector(struct drm_device *dev,
> >       struct radeon_connector *radeon_connector;
> >       struct i2c_adapter *ddc = NULL;
> >       uint32_t subpixel_order = SubPixelNone;
> > +     bool detected_hpd_without_ddc = false;
> >
> >       if (connector_type == DRM_MODE_CONNECTOR_Unknown)
> >               return;
> > @@ -2414,6 +2417,7 @@ radeon_add_legacy_connector(struct drm_device *dev,
> >       radeon_connector->devices = supported_device;
> >       radeon_connector->connector_object_id = connector_object_id;
> >       radeon_connector->hpd = *hpd;
> > +     radeon_connector->detected_hpd_without_ddc = detected_hpd_without_ddc;
> >
> >       switch (connector_type) {
> >       case DRM_MODE_CONNECTOR_VGA:
>