Re: [PATCH 10/60] drm/bridge: Add bridge driver for display connectors

[Sam Ravnborg <sam@ravnborg.org>]

Hi Laurent.

Two small details, see below.

	Sam

On Sun, Jul 07, 2019 at 09:18:47PM +0300, Laurent Pinchart wrote:
> Display connectors are modelled in DT as a device node, but have so far
> been handled manually in several bridge drivers. This resulted in
> duplicate code in several bridge drivers, with slightly different (and
> thus confusing) logics.
> 
> In order to fix this, implement a bridge driver for display connectors.
> The driver centralises logic for the DVI, HDMI, VGAn composite and
> S-video connectors and exposes corresponding bridge operations.
> 
> This driver in itself doesn't solve the issue completely, changes in
> bridge and display controller drivers are needed to make use of the new
> connector driver.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> ---
>  drivers/gpu/drm/bridge/Kconfig             |  11 +
>  drivers/gpu/drm/bridge/Makefile            |   1 +
>  drivers/gpu/drm/bridge/display-connector.c | 327 +++++++++++++++++++++
>  3 files changed, 339 insertions(+)
>  create mode 100644 drivers/gpu/drm/bridge/display-connector.c
> 
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index a78392e2dbb9..295a62f65ef9 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -37,6 +37,17 @@ config DRM_CDNS_DSI
>  	  Support Cadence DPI to DSI bridge. This is an internal
>  	  bridge and is meant to be directly embedded in a SoC.
>  
> +config DRM_DISPLAY_CONNECTOR
> +	tristate "Display connector support"
> +	depends on OF
> +	help
> +	  Driver for display connectors with support for DDC and hot-plug
> +	  detection. Most display controller handle display connectors
> +	  internally and don't need this driver, but the DRM subsystem is
> +	  moving towards separating connector handling from display controllers
> +	  on ARM-based platforms. Saying Y here when this driver is not needed
> +	  will not cause any issue.
> +
>  config DRM_LVDS_ENCODER
>  	tristate "Transparent parallel to LVDS encoder support"
>  	depends on OF
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index 6ff7f2adbb0e..e5987b3aaf62 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -1,6 +1,7 @@
>  # SPDX-License-Identifier: GPL-2.0
>  obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o
>  obj-$(CONFIG_DRM_CDNS_DSI) += cdns-dsi.o
> +obj-$(CONFIG_DRM_DISPLAY_CONNECTOR) += display-connector.o
>  obj-$(CONFIG_DRM_LVDS_ENCODER) += lvds-encoder.o
>  obj-$(CONFIG_DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW) += megachips-stdpxxxx-ge-b850v3-fw.o
>  obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
> diff --git a/drivers/gpu/drm/bridge/display-connector.c b/drivers/gpu/drm/bridge/display-connector.c
> new file mode 100644
> index 000000000000..2e1e7ee89275
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/display-connector.c
> @@ -0,0 +1,327 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> + */
> +
...
> +
> +static void display_connector_hpd_enable(struct drm_bridge *bridge)
> +{
> +}
> +
> +static void display_connector_hpd_disable(struct drm_bridge *bridge)
> +{
> +}

It seems wrong that a new driver needs empty implementation of
hpd_enable() and hpd_disable().
I noticed the same in a later patch too.

Can we do without these empty functions?

> +
> +static const struct drm_bridge_funcs display_connector_bridge_funcs = {
> +	.attach = display_connector_attach,
> +	.detect = display_connector_detect,
> +	.get_edid = display_connector_get_edid,
> +	.hpd_enable = display_connector_hpd_enable,
> +	.hpd_disable = display_connector_hpd_disable,
> +};
> +
> +	struct display_connector *conn = arg;
> +	struct drm_bridge *bridge = &conn->bridge;
> +
> +	drm_bridge_hpd_notify(bridge, display_connector_detect(bridge));
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static const char *display_connector_type_name(struct display_connector *conn)
> +{
> +	switch (conn->bridge.type) {
> +	case DRM_MODE_CONNECTOR_Composite:
> +		return "Composite";
> +	case DRM_MODE_CONNECTOR_DVIA:
> +		return "DVI-A";
> +	case DRM_MODE_CONNECTOR_DVID:
> +		return "DVI-D";
> +	case DRM_MODE_CONNECTOR_DVII:
> +		return "DVI-I";
> +	case DRM_MODE_CONNECTOR_HDMIA:
> +		return "HDMI-A";
> +	case DRM_MODE_CONNECTOR_HDMIB:
> +		return "HDMI-B";
> +	case DRM_MODE_CONNECTOR_SVIDEO:
> +		return "S-Video";
> +	case DRM_MODE_CONNECTOR_VGA:
> +		return "VGA";
> +	default:
> +		return "unknown";
> +	}
> +}
We already have the relation DRM_MODE_CONNECTOR <=> name in drm_connector -
see drm_connector_enum_list.

Add a small function in drm_connector.c get the name, so we do not hardcode the
name twice?

	Sam
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