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From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Date: Sun, 3 Mar 2024 22:37:52 +0200
Message-ID: <CAA8EJppZRABYGuoDc-6e6VMwtAo3LvEyDpsHdkHFckrR=q+0ig@mail.gmail.com>
Subject: Re: [PATCH] drm/bridge: Select DRM_KMS_HELPER for DRM_PANEL_BRIDGE
To: Luca Weiss <luca.weiss@fairphone.com>
Cc: neil.armstrong@linaro.org, Andrzej Hajda <andrzej.hajda@intel.com>, 
	Robert Foss <rfoss@kernel.org>, Laurent Pinchart <Laurent.pinchart@ideasonboard.com>, 
	Jonas Karlman <jonas@kwiboo.se>, Jernej Skrabec <jernej.skrabec@gmail.com>, 
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>, Maxime Ripard <mripard@kernel.org>, 
	Thomas Zimmermann <tzimmermann@suse.de>, David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>, 
	~postmarketos/upstreaming@lists.sr.ht, phone-devel@vger.kernel.org, 
	dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
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On Thu, 29 Feb 2024 at 11:27, Luca Weiss <luca.weiss@fairphone.com> wrote:
>
> On Wed Jan 17, 2024 at 9:59 AM CET, Luca Weiss wrote:
> > On Mon Jan 15, 2024 at 9:43 AM CET, Neil Armstrong wrote:
> > > Hi Luca,
> > >
> > > On 11/01/2024 13:38, Luca Weiss wrote:
> > > > Since the kconfig symbol of DRM_PANEL_BRIDGE is only adding
> > > > bridge/panel.o to drm_kms_helper object, we need to select
> > > > DRM_KMS_HELPER to make sure the file is actually getting built.
> > > >
> > > > Otherwise with certain defconfigs e.g. devm_drm_of_get_bridge will not
> > > > be properly available:
> > > >
> > > >    aarch64-linux-gnu-ld: drivers/phy/qualcomm/phy-qcom-qmp-combo.o: in function `qmp_combo_bridge_attach':
> > > >    drivers/phy/qualcomm/phy-qcom-qmp-combo.c:3204:(.text+0x8f4): undefined reference to `devm_drm_of_get_bridge'
> > > >
> > > > Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
> > > > ---
> > > > I can see "depends on DRM_KMS_HELPER" was removed with commit
> > > > 3c3384050d68 ("drm: Don't make DRM_PANEL_BRIDGE dependent on DRM_KMS_HELPERS")

Could you please make sure that the usecase described in the mentioned
commit message doesn't get broken by your change?

> > > >
> > > > I'm not too familiar with Kconfig but it feels more correct if
> > > > PHY_QCOM_QMP_COMBO selects DRM_PANEL_BRIDGE that that's enough; and it
> > > > doesn't also has to explicitly select DRM_KMS_HELPER because of how the
> > > > objects are built in the Makefile.
> > > >
> > > > Alternatively solution to this patch could be adjusting this line in
> > > > include/drm/drm_bridge.h:
> > > >
> > > >    -#if defined(CONFIG_OF) && defined(CONFIG_DRM_PANEL_BRIDGE)
> > > >    +#if defined(CONFIG_OF) && defined(CONFIG_DRM_PANEL_BRIDGE) && defined(CONFIG_DRM_KMS_HELPER)
> > > >     struct drm_bridge *devm_drm_of_get_bridge(struct device *dev, struct device_node *node,
> > > >                                              u32 port, u32 endpoint);
> > > >
> > > > .. and then selecting DRM_KMS_HELPER for PHY_QCOM_QMP_COMBO.
> > > >
> > > > But I think the solution in this patch is better. Let me know what you
> > > > think.
> > >
> > > I think this is no more the case after on linux-next:
> > > 35921910bbd0 phy: qcom: qmp-combo: switch to DRM_AUX_BRIDGE
> > >
> > > But could you still check ?
> >
> > On next-20240117 the error happens in the aux-bridge file instead then.
> >
> > aarch64-linux-gnu-ld: drivers/gpu/drm/bridge/aux-bridge.o: in function `drm_aux_bridge_probe':
> > drivers/gpu/drm/bridge/aux-bridge.c:115:(.text+0xe0): undefined reference to `devm_drm_of_get_bridge'
> >
> > I'm attaching the defconfig with which I can reproduce this but it's
> > really just DRM_KMS_HELPER=n and PHY_QCOM_QMP_COMBO=y I believe.
>
> Hi Neil,
>
> Ping on this patch
>
> Regards
> Luca
>
> >
> > Regards
> > Luca
> >
> >
> > >
> > > Neil
> > >
> > > > ---
> > > >   drivers/gpu/drm/bridge/Kconfig | 1 +
> > > >   1 file changed, 1 insertion(+)
> > > >
> > > > diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> > > > index ac9ec5073619..ae782b427829 100644
> > > > --- a/drivers/gpu/drm/bridge/Kconfig
> > > > +++ b/drivers/gpu/drm/bridge/Kconfig
> > > > @@ -8,6 +8,7 @@ config DRM_BRIDGE
> > > >   config DRM_PANEL_BRIDGE
> > > >           def_bool y
> > > >           depends on DRM_BRIDGE
> > > > + select DRM_KMS_HELPER
> > > >           select DRM_PANEL
> > > >           help
> > > >             DRM bridge wrapper of DRM panels
> > > >
> > > > ---
> > > > base-commit: b9c3a1fa6fb324e691a03cf124b79f4842e65d76
> > > > change-id: 20240111-drm-panel-bridge-fixup-5c2977fb969f
> > > >
> > > > Best regards,
>


-- 
With best wishes
Dmitry