Re: [PATCH v6 5/9] drm/vc4: hdmi: Create a custom connector state

[Dave Stevenson <dave.stevenson@raspberrypi.com>]

Hi Maxime

On Thu, 10 Dec 2020 at 14:23, Maxime Ripard <maxime@cerno.tech> wrote:
>
> When run with a higher bpc than 8, the clock of the HDMI controller needs
> to be adjusted. Let's create a connector state that will be used at
> atomic_check and atomic_enable to compute and store the clock rate
> associated to the state.
>
> Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
> Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
> Signed-off-by: Maxime Ripard <maxime@cerno.tech>
> ---
>  drivers/gpu/drm/vc4/vc4_hdmi.c | 33 ++++++++++++++++++++++++++++++---
>  drivers/gpu/drm/vc4/vc4_hdmi.h | 10 ++++++++++
>  2 files changed, 40 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index 61039cc89d9d..8978df3f0ca4 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -170,10 +170,37 @@ static int vc4_hdmi_connector_get_modes(struct drm_connector *connector)
>
>  static void vc4_hdmi_connector_reset(struct drm_connector *connector)
>  {
> -       drm_atomic_helper_connector_reset(connector);
> +       struct vc4_hdmi_connector_state *old_state =
> +               conn_state_to_vc4_hdmi_conn_state(connector->state);
> +       struct vc4_hdmi_connector_state *new_state =
> +               kzalloc(sizeof(*conn_state), GFP_KERNEL);
>
>         if (connector->state)
> -               drm_atomic_helper_connector_tv_reset(connector);
> +               __drm_atomic_helper_connector_destroy_state(connector->state);
> +
> +       kfree(old_state);
> +
> +       if (!new_state)
> +               return;

This has changed since v5 that I added my R-B to.

So we no longer call __drm_atomic_helper_connector_reset should the
kzalloc fail. Doesn't that mean connector->state is still set to
old_state? Except we've called kfree on that and it's therefore
invalid.

Calling __drm_atomic_helper_connector_reset unconditionally is fine as
it checks for the new pointer being NULL before dereferencing, but
always assigns it to connector->state.
Calling drm_atomic_helper_connector_tv_reset when connector->state =
NULL isn't safe.

> +       __drm_atomic_helper_connector_reset(connector, &new_state->base);

Put the if (!new_state) return; here?
Patch 9/9 can set the max_bpc and max_bpc_requested field here too.

  Dave

> +       drm_atomic_helper_connector_tv_reset(connector);
> +}
> +
> +static struct drm_connector_state *
> +vc4_hdmi_connector_duplicate_state(struct drm_connector *connector)
> +{
> +       struct drm_connector_state *conn_state = connector->state;
> +       struct vc4_hdmi_connector_state *vc4_state = conn_state_to_vc4_hdmi_conn_state(conn_state);
> +       struct vc4_hdmi_connector_state *new_state;
> +
> +       new_state = kzalloc(sizeof(*new_state), GFP_KERNEL);
> +       if (!new_state)
> +               return NULL;
> +
> +       __drm_atomic_helper_connector_duplicate_state(connector, &new_state->base);
> +
> +       return &new_state->base;
>  }
>
>  static const struct drm_connector_funcs vc4_hdmi_connector_funcs = {
> @@ -181,7 +208,7 @@ static const struct drm_connector_funcs vc4_hdmi_connector_funcs = {
>         .fill_modes = drm_helper_probe_single_connector_modes,
>         .destroy = vc4_hdmi_connector_destroy,
>         .reset = vc4_hdmi_connector_reset,
> -       .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
> +       .atomic_duplicate_state = vc4_hdmi_connector_duplicate_state,
>         .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
>  };
>
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.h b/drivers/gpu/drm/vc4/vc4_hdmi.h
> index 0526a9cf608a..2cf5362052e2 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.h
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.h
> @@ -180,6 +180,16 @@ encoder_to_vc4_hdmi(struct drm_encoder *encoder)
>         return container_of(_encoder, struct vc4_hdmi, encoder);
>  }
>
> +struct vc4_hdmi_connector_state {
> +       struct drm_connector_state      base;
> +};
> +
> +static inline struct vc4_hdmi_connector_state *
> +conn_state_to_vc4_hdmi_conn_state(struct drm_connector_state *conn_state)
> +{
> +       return container_of(conn_state, struct vc4_hdmi_connector_state, base);
> +}
> +
>  void vc4_hdmi_phy_init(struct vc4_hdmi *vc4_hdmi,
>                        struct drm_display_mode *mode);
>  void vc4_hdmi_phy_disable(struct vc4_hdmi *vc4_hdmi);
> --
> 2.28.0
>

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