[PATCH 1/6] drm: allow real encoder to be passed for drm_writeback_connector

[Dmitry Baryshkov]

On Fri, 11 Mar 2022 at 04:50, Abhinav Kumar <quic_abhinavk at quicinc.com> wrote:
>
> For some vendor driver implementations, display hardware can
> be shared between the encoder used for writeback and the physical
> display.
>
> In addition resources such as clocks and interrupts can
> also be shared between writeback and the real encoder.
>
> To accommodate such vendor drivers and hardware, allow
> real encoder to be passed for drm_writeback_connector.
>
> Co-developed-by: Kandpal Suraj <suraj.kandpal at intel.com>
> Signed-off-by: Abhinav Kumar <quic_abhinavk at quicinc.com>
> ---
>  drivers/gpu/drm/drm_writeback.c |  8 ++++----
>  include/drm/drm_writeback.h     | 13 +++++++++++--
>  2 files changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_writeback.c b/drivers/gpu/drm/drm_writeback.c
> index dccf4504..4dad687 100644
> --- a/drivers/gpu/drm/drm_writeback.c
> +++ b/drivers/gpu/drm/drm_writeback.c
> @@ -189,8 +189,8 @@ int drm_writeback_connector_init(struct drm_device *dev,
>         if (IS_ERR(blob))
>                 return PTR_ERR(blob);
>
> -       drm_encoder_helper_add(&wb_connector->encoder, enc_helper_funcs);
> -       ret = drm_encoder_init(dev, &wb_connector->encoder,
> +       drm_encoder_helper_add(wb_connector->encoder, enc_helper_funcs);
> +       ret = drm_encoder_init(dev, wb_connector->encoder,
>                                &drm_writeback_encoder_funcs,
>                                DRM_MODE_ENCODER_VIRTUAL, NULL);

If the encoder is provided by a separate driver, it might use a
different set of encoder funcs.

I'd suggest checking whether the wb_connector->encoder is NULL here.
If it is, allocate one using drmm_kzalloc and init it.
If it is not NULL, assume that it has been initialized already, so
skip the drm_encoder_init() and just call the drm_encoder_helper_add()

>         if (ret)
> @@ -204,7 +204,7 @@ int drm_writeback_connector_init(struct drm_device *dev,
>                 goto connector_fail;
>
>         ret = drm_connector_attach_encoder(connector,
> -                                               &wb_connector->encoder);
> +                                               wb_connector->encoder);
>         if (ret)
>                 goto attach_fail;
>
> @@ -233,7 +233,7 @@ int drm_writeback_connector_init(struct drm_device *dev,
>  attach_fail:
>         drm_connector_cleanup(connector);
>  connector_fail:
> -       drm_encoder_cleanup(&wb_connector->encoder);
> +       drm_encoder_cleanup(wb_connector->encoder);
>  fail:
>         drm_property_blob_put(blob);
>         return ret;
> diff --git a/include/drm/drm_writeback.h b/include/drm/drm_writeback.h
> index 9697d27..0ba266e 100644
> --- a/include/drm/drm_writeback.h
> +++ b/include/drm/drm_writeback.h
> @@ -25,13 +25,22 @@ struct drm_writeback_connector {
>         struct drm_connector base;
>
>         /**
> -        * @encoder: Internal encoder used by the connector to fulfill
> +        * @encoder: handle to drm_encoder used by the connector to fulfill
>          * the DRM framework requirements. The users of the
>          * @drm_writeback_connector control the behaviour of the @encoder
>          * by passing the @enc_funcs parameter to drm_writeback_connector_init()
>          * function.
> +        *
> +        * For some vendor drivers, the hardware resources are shared between
> +        * writeback encoder and rest of the display pipeline.
> +        * To accommodate such cases, encoder is a handle to the real encoder
> +        * hardware.
> +        *
> +        * For current existing writeback users, this shall continue to be the
> +        * embedded encoder for the writeback connector.
> +        *
>          */
> -       struct drm_encoder encoder;
> +       struct drm_encoder *encoder;
>
>         /**
>          * @pixel_formats_blob_ptr:
> --
> 2.7.4
>


-- 
With best wishes
Dmitry