[PATCH v3 2/4] drm/bridge: imx8mp-hdmi-tx: switch to bridge DRM_BRIDGE_ATTACH_NO_CONNECTOR

[Dmitry Baryshkov]

On Fri, Jan 03, 2025 at 12:22:34AM +0100, Marek Vasut wrote:
> On 1/2/25 5:55 AM, Dmitry Baryshkov wrote:
> > On Tue, Dec 31, 2024 at 08:28:49PM +0100, Marek Vasut wrote:
> > > The dw-hdmi output_port is set to 1 in order to look for a connector
> > > next bridge in order to get DRM_BRIDGE_ATTACH_NO_CONNECTOR working.
> > > The output_port set to 1 makes the DW HDMI driver core look up the
> > > next bridge in DT, where the next bridge is often the hdmi-connector .
> > > 
> > > Similar to 0af5e0b41110 ("drm/meson: encoder_hdmi: switch to bridge DRM_BRIDGE_ATTACH_NO_CONNECTOR")
> > > 
> > > Note that looking at the upstream arch/arm64/boot/dts/freescale/imx8mp*dts ,
> > > the oldest commit which adds HDMI support is commit:
> > > 
> > > 3e67a1ddd56d ("arm64: dts: imx8mp: Enable HDMI on TQMa8MPxL/MBa8MPxL")
> > > 
> > > That already contains the HDMI connector node. Most follow up additions
> > > of HDMI support to another devices has been a variation of the same commit,
> > > including connector node, which is the proper way of eanbling HDMI on the
> > > i.MX8MP.
> > > 
> > > The rest should be covered by output_port_optional which should make systems
> > > with DTs without HDMI connector node work, but such DTs should be updated and
> > > the HDMI connector node should be added.
> > > 
> > > Signed-off-by: Marek Vasut <marex at denx.de>
> > > ---
> > > Cc: Andrzej Hajda <andrzej.hajda at intel.com>
> > > Cc: David Airlie <airlied at gmail.com>
> > > Cc: Fabio Estevam <festevam at gmail.com>
> > > Cc: Jernej Skrabec <jernej.skrabec at gmail.com>
> > > Cc: Jonas Karlman <jonas at kwiboo.se>
> > > Cc: Laurent Pinchart <Laurent.pinchart at ideasonboard.com>
> > > Cc: Liu Ying <victor.liu at nxp.com>
> > > Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> > > Cc: Maxime Ripard <mripard at kernel.org>
> > > Cc: Neil Armstrong <neil.armstrong at linaro.org>
> > > Cc: Pengutronix Kernel Team <kernel at pengutronix.de>
> > > Cc: Robert Foss <rfoss at kernel.org>
> > > Cc: Sascha Hauer <s.hauer at pengutronix.de>
> > > Cc: Shawn Guo <shawnguo at kernel.org>
> > > Cc: Simona Vetter <simona at ffwll.ch>
> > > Cc: Stefan Agner <stefan at agner.ch>
> > > Cc: Thomas Zimmermann <tzimmermann at suse.de>
> > > Cc: dri-devel at lists.freedesktop.org
> > > Cc: imx at lists.linux.dev
> > > Cc: linux-arm-kernel at lists.infradead.org
> > > ---
> > > V2: No change
> > > V3: - Update commit message
> > >      - Move select DRM_DISPLAY_CONNECTOR to DRM_IMX8MP_DW_HDMI_BRIDGE
> > >      - Enable output_port_optional
> > > ---
> > >   drivers/gpu/drm/bridge/imx/Kconfig          | 1 +
> > >   drivers/gpu/drm/bridge/imx/imx8mp-hdmi-tx.c | 2 ++
> > >   2 files changed, 3 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/bridge/imx/Kconfig b/drivers/gpu/drm/bridge/imx/Kconfig
> > > index 9a480c6abb856..db5c8a76193ac 100644
> > > --- a/drivers/gpu/drm/bridge/imx/Kconfig
> > > +++ b/drivers/gpu/drm/bridge/imx/Kconfig
> > > @@ -17,6 +17,7 @@ config DRM_IMX8MP_DW_HDMI_BRIDGE
> > >   	tristate "Freescale i.MX8MP HDMI-TX bridge support"
> > >   	depends on OF
> > >   	depends on COMMON_CLK
> > > +	select DRM_DISPLAY_CONNECTOR
> > 
> > I was going to write that it is not to be selected by anybody, but then
> > I stumbled upon meson driver, which also selects the symbol.
> > 
> > I still think that it is not to be selected by your driver as there is
> > no direct dependency (and there can be other bridges inbetween or the
> > bridge chain can end up with some other bridge). Such decisions belong
> > to defconfig or distribution's kernel config file.
> Wouldn't that only lead to unnecessary surprises on user side ?

This is of no concerns to Kconfig. You can't select all drivers that can
possibly be used with your platform / driver. `git grep
DRM_DISPLAY_CONNECTOR`.

-- 
With best wishes
Dmitry