Re: [PATCH 01/20] drm/atomic: Fix remaining places where !funcs->best_encoder is valid

Boris Brezillon
2016-06-03T07:36:15Z

On Fri, 03 Jun 2016 00:05:46 +0300
Laurent Pinchart <laurent.pinchart@ideasonboard.com> wrote:

> Hi Boris,
>
> Thank you for the patch.
>
> On Thursday 02 Jun 2016 16:31:28 Boris Brezillon wrote:
> > Adapt drm_pick_crtcs() and update_connector_routing() to fallback to
> > drm_atomic_helper_best_encoder() if funcs->best_encoder() is NULL so
> > that DRM drivers can leave this hook unassigned if they know they want
> > to use drm_atomic_helper_best_encoder().
>
> Could you please update include/drm/drm_modeset_helper_vtables.h to document
> this new behaviour ?

Sure.

>
> The only drawback I see in this patch is the additional object lookup
> performed by drm_atomic_helper_best_encoder() at runtime. I wonder if we could
> somehow cache the information, as the assignment can't change when there's a
> 1:1 correspondence between encoders and connectors.
>
> > Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> > ---
> > drivers/gpu/drm/drm_atomic_helper.c | 4 +++-
> > drivers/gpu/drm/drm_fb_helper.c | 13 ++++++++++++-
> > 2 files changed, 15 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_atomic_helper.c
> > b/drivers/gpu/drm/drm_atomic_helper.c index f6a3350..849d029 100644
> > --- a/drivers/gpu/drm/drm_atomic_helper.c
> > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > @@ -300,8 +300,10 @@ update_connector_routing(struct drm_atomic_state
> > *state, if (funcs->atomic_best_encoder)
> > new_encoder = funcs->atomic_best_encoder(connector,
> > connector_state);
> > - else
> > + else if (funcs->best_encoder)
> > new_encoder = funcs->best_encoder(connector);
> > + else
> > + new_encoder = drm_atomic_helper_best_encoder(connector);
> >
> > if (!new_encoder) {
> > DRM_DEBUG_ATOMIC("No suitable encoder found for [CONNECTOR:%d:%s]\n",
> > diff --git a/drivers/gpu/drm/drm_fb_helper.c
> > b/drivers/gpu/drm/drm_fb_helper.c index 7c2eb75..d44389a 100644
> > --- a/drivers/gpu/drm/drm_fb_helper.c
> > +++ b/drivers/gpu/drm/drm_fb_helper.c
> > @@ -2000,7 +2000,18 @@ static int drm_pick_crtcs(struct drm_fb_helper
> > *fb_helper, my_score++;
> >
> > connector_funcs = connector->helper_private;
> > - encoder = connector_funcs->best_encoder(connector);
> > +
> > + /*
> > + * If the DRM device implements atomic hooks and ->best_encoder() is
> > + * NULL we fallback to the default drm_atomic_helper_best_encoder()
> > + * helper.
> > + */
> > + if (fb_helper->dev->mode_config.funcs->atomic_commit &&
> > + !connector_funcs->best_encoder)
> > + encoder = drm_atomic_helper_best_encoder(connector);
> > + else
> > + encoder = connector_funcs->best_encoder(connector);
> > +
> > if (!encoder)
> > goto out;
>

--
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering