Re: [PATCH v4 02/12] drm/client: Restrict the plane_state scope

[Maxime Ripard <maxime.ripard@bootlin.com>]

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Hi Jani,

On Fri, Jun 14, 2019 at 03:28:59PM +0300, Jani Nikula wrote:
> On Fri, 14 Jun 2019, Maxime Ripard <maxime.ripard@bootlin.com> wrote:
> > The drm_client_modeset_commit_atomic function uses two times the
> > plane_state variable in inner blocks of code, but the variable has a scope
> > global to this function.
> >
> > This will lead to inadvertent devs to reuse the variable in the second
> > block with the value left by the first, without any warning from the
> > compiler since value would have been initialized.
> >
> > Fix this by moving the variable declaration to the proper scope.
>
> This is an improvement, but I'd consider renaming also to not shadow
> variables.
>
> > Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
> > ---
> >  drivers/gpu/drm/drm_client_modeset.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/drm_client_modeset.c b/drivers/gpu/drm/drm_client_modeset.c
> > index 006bf7390e7d..8264c3a732b0 100644
> > --- a/drivers/gpu/drm/drm_client_modeset.c
> > +++ b/drivers/gpu/drm/drm_client_modeset.c
> > @@ -861,7 +861,6 @@ EXPORT_SYMBOL(drm_client_panel_rotation);
> >  static int drm_client_modeset_commit_atomic(struct drm_client_dev *client, bool active)
> >  {
> >  	struct drm_device *dev = client->dev;
> > -	struct drm_plane_state *plane_state;
> >  	struct drm_plane *plane;
> >  	struct drm_atomic_state *state;
> >  	struct drm_modeset_acquire_ctx ctx;
> > @@ -879,6 +878,8 @@ static int drm_client_modeset_commit_atomic(struct drm_client_dev *client, bool
> >  	state->acquire_ctx = &ctx;
> >  retry:
> >  	drm_for_each_plane(plane, dev) {
> > +		struct drm_plane_state *plane_state;
> > +
> >  		plane_state = drm_atomic_get_plane_state(state, plane);
> >  		if (IS_ERR(plane_state)) {
> >  			ret = PTR_ERR(plane_state);
> > @@ -901,6 +902,8 @@ static int drm_client_modeset_commit_atomic(struct drm_client_dev *client, bool
> >  		unsigned int rotation;
> >
> >  		if (drm_client_panel_rotation(mode_set, &rotation)) {
> > +			struct drm_plane_state *plane_state;
> > +

That's not super clear from that patch, but this variable will not
shadow the first one.

The code layout is pretty much this one:

loop () {
  struct drm_plane_state *plane_state;

  [...]
}

loop () {
  loop () {
    struct drm_plane_state *plane_state;

    [...]
  }
}

so the shadowing doesn't exist

Maxime

--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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