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

Laurent Pinchart
2016-06-02T21:05:46Z

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 ?

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;

--
Regards,

Laurent Pinchart