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SubjectRe: [PATCH RFC 2/5] drm/bridge: add encoder support to specify bridge input format
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Hi Laurent,

On 29/03/2019 11:42, Neil Armstrong wrote:
> This patch adds a new format_set() callback to the bridge ops permitting
> the encoder to specify the new input format and encoding.

Is this something better ? This doesn't violate the layering anymore,
do you have any thoughts about this new API ?

Neil

>
> This allows supporting the very specific HDMI2.0 YUV420 output mode
> when the bridge cannot convert from RGB or YUV444 to YUV420.
>
> In this case, the encode must downsample before the bridge and must
> specify the bridge the new input bus format differs.
>
> This will also help supporting the YUV420 mode where the bridge cannot
> downsample, and also support 10bit, 12bit and 16bit output modes
> when the bridge cannot convert between different bit depths.
>
> Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
> ---
> drivers/gpu/drm/drm_bridge.c | 35 +++++++++++++++++++++++++++++++++++
> include/drm/drm_bridge.h | 19 +++++++++++++++++++
> 2 files changed, 54 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index 138b2711d389..b2ce2d3d070e 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -307,6 +307,41 @@ void drm_bridge_mode_set(struct drm_bridge *bridge,
> }
> EXPORT_SYMBOL(drm_bridge_mode_set);
>
> +/**
> + * drm_bridge_format_set - setup with proposed input format and encoding for
> + * all bridges in the encoder chain
> + * @bridge: bridge control structure
> + * @input_bus_format: proposed input bus format for the bridge
> + * @input_encoding: proposed input encoding for this bridge
> + *
> + * Calls &drm_bridge_funcs.format_set op for all the bridges in the
> + * encoder chain, starting from the first bridge to the last.
> + *
> + * Note: the bridge passed should be the one closest to the encoder
> + *
> + * RETURNS:
> + * true on success, false if one of the bridge cannot handle the format
> + */
> +bool drm_bridge_format_set(struct drm_bridge *bridge,
> + const u32 input_bus_format,
> + const u32 input_encoding)
> +{
> + bool ret = true;
> +
> + if (!bridge)
> + return true;
> +
> + if (bridge->funcs->format_set)
> + ret = bridge->funcs->format_set(bridge, input_bus_format,
> + input_encoding);
> + if (ret)
> + return ret;
> +
> + return drm_bridge_format_set(bridge->next, input_bus_format,
> + input_encoding);
> +}
> +EXPORT_SYMBOL(drm_bridge_format_set);
> +
> /**
> * drm_bridge_pre_enable - prepares for enabling all
> * bridges in the encoder chain
> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> index 9da8c93f7976..223253b15763 100644
> --- a/include/drm/drm_bridge.h
> +++ b/include/drm/drm_bridge.h
> @@ -198,6 +198,22 @@ struct drm_bridge_funcs {
> void (*mode_set)(struct drm_bridge *bridge,
> const struct drm_display_mode *mode,
> const struct drm_display_mode *adjusted_mode);
> +
> + /**
> + * @format_set:
> + *
> + * This callback should configure the bridge for the given input bus
> + * format and encoding. It is called after the @format_set callback
> + * for the preceding element in the display pipeline has been called
> + * already. If the bridge is the first element then this would be
> + * &drm_encoder_helper_funcs.format_set. The display pipe (i.e.
> + * clocks and timing signals) is off when this function is called.
> + *
> + * @returns: true in success, false is a bridge refuses the format
> + */
> + bool (*format_set)(struct drm_bridge *bridge,
> + const u32 input_bus_format,
> + const u32 input_encoding);
> /**
> * @pre_enable:
> *
> @@ -312,6 +328,9 @@ void drm_bridge_post_disable(struct drm_bridge *bridge);
> void drm_bridge_mode_set(struct drm_bridge *bridge,
> const struct drm_display_mode *mode,
> const struct drm_display_mode *adjusted_mode);
> +bool drm_bridge_format_set(struct drm_bridge *bridge,
> + const u32 input_bus_format,
> + const u32 input_encoding);
> void drm_bridge_pre_enable(struct drm_bridge *bridge);
> void drm_bridge_enable(struct drm_bridge *bridge);
>
>

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