linux-kernel - Re: [PATCH 02/36] drm/plane: Make ->atomic

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Date:	Fri, 23 Jan 2015 10:18:57 +0100
From:	Thierry Reding <thierry.reding@...il.com>
To:	Rob Clark <robdclark@...il.com>
Cc:	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 02/36] drm/plane: Make ->atomic_update() mandatory

On Tue, Jan 20, 2015 at 08:51:15AM -0500, Rob Clark wrote:
> On Tue, Jan 20, 2015 at 5:48 AM, Thierry Reding
> <thierry.reding@...il.com> wrote:
> > From: Thierry Reding <treding@...dia.com>
> >
> > There is no use-case where it would be useful for drivers not to
> > implement this function and the transitional plane helpers already
> > require drivers to provide an implementation.
> >
> > Signed-off-by: Thierry Reding <treding@...dia.com>
> > ---
> >  drivers/gpu/drm/drm_atomic_helper.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> > index d467185f7942..010661f23035 100644
> > --- a/drivers/gpu/drm/drm_atomic_helper.c
> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > @@ -1108,7 +1108,7 @@ void drm_atomic_helper_commit_planes(struct drm_device *dev,
> >
> >                 funcs = plane->helper_private;
> >
> > -               if (!funcs || !funcs->atomic_update)
> > +               if (!funcs)
> 
> maybe WARN_ON() here.. or drm_universal_plane_init(), or somewhere,
> for missing mandatory fxns would be a nice thing to avoid explosions
> under console_lock for first modeset?

WARN_ON() here isn't going to do you any good under console_lock and
may drivers use drm_universal_plane_init() without having converted to
atomic mode-setting.

Adding a comment to kerneldoc that it's mandatory is probably the best
we can do here.

Thierry

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