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Message-ID: <29f0cd8a739adb977ddde99af975738329cbee83.camel@redhat.com>
Subject: Re: [PATCH 15/30] drm/dp: Add backpointer to drm_device in
 drm_dp_aux
From:   Lyude Paul <lyude@redhat.com>
Reply-To: lyude@redhat.com
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc:     intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        amd-gfx@lists.freedesktop.org, nouveau@lists.freedesktop.org,
        Ville =?ISO-8859-1?Q?Syrj=E4l=E4?= 
        <ville.syrjala@linux.intel.com>,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Alex Deucher <alexander.deucher@amd.com>,
        Christian =?ISO-8859-1?Q?K=F6nig?= <christian.koenig@amd.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Harry Wentland <harry.wentland@amd.com>,
        Leo Li <sunpeng.li@amd.com>,
        Andrzej Hajda <a.hajda@samsung.com>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Jonas Karlman <jonas@kwiboo.se>,
        Jernej Skrabec <jernej.skrabec@siol.net>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rob Clark <robdclark@gmail.com>, Sean Paul <sean@poorly.run>,
        Ben Skeggs <bskeggs@redhat.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Hyun Kwon <hyun.kwon@xilinx.com>,
        Michal Simek <michal.simek@xilinx.com>,
        Luben Tuikov <luben.tuikov@amd.com>,
        Oleg Vasilev <oleg.vasilev@intel.com>,
        Emil Velikov <emil.velikov@collabora.com>,
        Mikita Lipski <mikita.lipski@amd.com>,
        Eryk Brol <eryk.brol@amd.com>,
        Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>,
        "Jerry (Fangzhi) Zuo" <Jerry.Zuo@amd.com>,
        Chris Park <Chris.Park@amd.com>,
        Pankaj Bharadiya <pankaj.laxminarayan.bharadiya@intel.com>,
        Sam Ravnborg <sam@ravnborg.org>,
        Boris Brezillon <boris.brezillon@collabora.com>,
        Torsten Duwe <duwe@lst.de>,
        Vasily Khoruzhick <anarsoul@gmail.com>,
        Joe Perches <joe@perches.com>, Icenowy Zheng <icenowy@aosc.io>,
        Tomi Valkeinen <tomi.valkeinen@ti.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Swapnil Jakhade <sjakhade@cadence.com>,
        Yuti Amonkar <yamonkar@cadence.com>,
        Julia Lawall <Julia.Lawall@inria.fr>,
        open list <linux-kernel@vger.kernel.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <linux-arm-msm@vger.kernel.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <freedreno@lists.freedesktop.org>,
        "open list:DRM DRIVERS FOR NVIDIA TEGRA" 
        <linux-tegra@vger.kernel.org>,
        "moderated list:ARM/ZYNQ ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>
Date:   Wed, 24 Feb 2021 15:40:41 -0500
In-Reply-To: <YDKklI3grZjn3dde@pendragon.ideasonboard.com>
References: <20210219215326.2227596-1-lyude@redhat.com>
         <20210219215326.2227596-16-lyude@redhat.com>
         <YDKklI3grZjn3dde@pendragon.ideasonboard.com>
Organization: Red Hat
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On Sun, 2021-02-21 at 20:21 +0200, Laurent Pinchart wrote:
> Hi Lyude,
> 
> Thank you for the patch.
> 
> On Fri, Feb 19, 2021 at 04:53:11PM -0500, Lyude Paul wrote:
> > This is something that we've wanted for a while now: the ability to
> > actually look up the respective drm_device for a given drm_dp_aux struct.
> > This will also allow us to transition over to using the drm_dbg_*() helpers
> > for debug message printing, as we'll finally have a drm_device to reference
> > for doing so.
> 
> Isn't it better to use the existing dev field ? If you have multiple DP
> outputs for one DRM device, using the DRM device name in debug messages
> won't tell which output the message corresponds to.

Well the thing is dev won't tell you that either - on most SoCs the DP AUX
adapter is it's own platform device that isn't a child of the DRM device. Also,
that's what the ability to name AUX channels is supposed to be there for.

> > Note that there is one limitation with this - because some DP AUX adapters
> > exist as platform devices which are initialized independently of their
> > respective DRM devices, one cannot rely on drm_dp_aux->drm_dev to always be
> > non-NULL until drm_dp_aux_register() has been called. We make sure to point
> > this out in the documentation for struct drm_dp_aux.
> > 
> > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > ---
> >  drivers/gpu/drm/amd/amdgpu/atombios_dp.c                 | 1 +
> >  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c  | 1 +
> >  drivers/gpu/drm/bridge/analogix/analogix-anx6345.c       | 1 +
> >  drivers/gpu/drm/bridge/analogix/analogix-anx78xx.c       | 1 +
> >  drivers/gpu/drm/bridge/analogix/analogix_dp_core.c       | 1 +
> >  drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c      | 1 +
> >  drivers/gpu/drm/bridge/tc358767.c                        | 1 +
> >  drivers/gpu/drm/bridge/ti-sn65dsi86.c                    | 1 +
> >  drivers/gpu/drm/drm_dp_aux_dev.c                         | 6 ++++++
> >  drivers/gpu/drm/drm_dp_mst_topology.c                    | 1 +
> >  drivers/gpu/drm/i915/display/intel_dp_aux.c              | 1 +
> >  drivers/gpu/drm/msm/edp/edp.h                            | 3 +--
> >  drivers/gpu/drm/msm/edp/edp_aux.c                        | 5 +++--
> >  drivers/gpu/drm/msm/edp/edp_ctrl.c                       | 2 +-
> >  drivers/gpu/drm/nouveau/nouveau_connector.c              | 1 +
> >  drivers/gpu/drm/radeon/atombios_dp.c                     | 1 +
> >  drivers/gpu/drm/tegra/dpaux.c                            | 1 +
> >  drivers/gpu/drm/xlnx/zynqmp_dp.c                         | 1 +
> >  include/drm/drm_dp_helper.h                              | 9 ++++++++-
> >  19 files changed, 33 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/amd/amdgpu/atombios_dp.c
> > b/drivers/gpu/drm/amd/amdgpu/atombios_dp.c
> > index a3ba9ca11e98..6d35da65e09f 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/atombios_dp.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/atombios_dp.c
> > @@ -188,6 +188,7 @@ void amdgpu_atombios_dp_aux_init(struct amdgpu_connector
> > *amdgpu_connector)
> >  {
> >         amdgpu_connector->ddc_bus->rec.hpd = amdgpu_connector->hpd.hpd;
> >         amdgpu_connector->ddc_bus->aux.transfer =
> > amdgpu_atombios_dp_aux_transfer;
> > +       amdgpu_connector->ddc_bus->aux.drm_dev = amdgpu_connector->base.dev;
> >         drm_dp_aux_init(&amdgpu_connector->ddc_bus->aux);
> >         amdgpu_connector->ddc_bus->has_aux = true;
> >  }
> > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > index 41b09ab22233..163641b44339 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > @@ -431,6 +431,7 @@ void amdgpu_dm_initialize_dp_connector(struct
> > amdgpu_display_manager *dm,
> >                           link_index);
> >         aconnector->dm_dp_aux.aux.transfer = dm_dp_aux_transfer;
> >         aconnector->dm_dp_aux.ddc_service = aconnector->dc_link->ddc;
> > +       aconnector->dm_dp_aux.aux.drm_dev = dm->ddev;
> >  
> >         drm_dp_aux_init(&aconnector->dm_dp_aux.aux);
> >         drm_dp_cec_register_connector(&aconnector->dm_dp_aux.aux,
> > diff --git a/drivers/gpu/drm/bridge/analogix/analogix-anx6345.c
> > b/drivers/gpu/drm/bridge/analogix/analogix-anx6345.c
> > index aa6cda458eb9..e33cd077595a 100644
> > --- a/drivers/gpu/drm/bridge/analogix/analogix-anx6345.c
> > +++ b/drivers/gpu/drm/bridge/analogix/analogix-anx6345.c
> > @@ -537,6 +537,7 @@ static int anx6345_bridge_attach(struct drm_bridge
> > *bridge,
> >         /* Register aux channel */
> >         anx6345->aux.name = "DP-AUX";
> >         anx6345->aux.dev = &anx6345->client->dev;
> > +       anx6345->aux.drm_dev = bridge->dev;
> >         anx6345->aux.transfer = anx6345_aux_transfer;
> >  
> >         err = drm_dp_aux_register(&anx6345->aux);
> > diff --git a/drivers/gpu/drm/bridge/analogix/analogix-anx78xx.c
> > b/drivers/gpu/drm/bridge/analogix/analogix-anx78xx.c
> > index f20558618220..5e6a0ed39199 100644
> > --- a/drivers/gpu/drm/bridge/analogix/analogix-anx78xx.c
> > +++ b/drivers/gpu/drm/bridge/analogix/analogix-anx78xx.c
> > @@ -905,6 +905,7 @@ static int anx78xx_bridge_attach(struct drm_bridge
> > *bridge,
> >         /* Register aux channel */
> >         anx78xx->aux.name = "DP-AUX";
> >         anx78xx->aux.dev = &anx78xx->client->dev;
> > +       anx78xx->aux.drm_dev = bridge->dev;
> >         anx78xx->aux.transfer = anx78xx_aux_transfer;
> >  
> >         err = drm_dp_aux_register(&anx78xx->aux);
> > diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> > b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> > index f115233b1cb9..550814ca2139 100644
> > --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> > +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> > @@ -1765,6 +1765,7 @@ int analogix_dp_bind(struct analogix_dp_device *dp,
> > struct drm_device *drm_dev)
> >         dp->aux.name = "DP-AUX";
> >         dp->aux.transfer = analogix_dpaux_transfer;
> >         dp->aux.dev = dp->dev;
> > +       dp->aux.drm_dev = drm_dev;
> >  
> >         ret = drm_dp_aux_register(&dp->aux);
> >         if (ret)
> > diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> > b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> > index d966a33743b5..fe821ad628ec 100644
> > --- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> > +++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> > @@ -1674,6 +1674,7 @@ static int cdns_mhdp_attach(struct drm_bridge *bridge,
> >  
> >         dev_dbg(mhdp->dev, "%s\n", __func__);
> >  
> > +       mhdp->aux.drm_dev = bridge->dev;
> >         ret = drm_dp_aux_register(&mhdp->aux);
> >         if (ret < 0)
> >                 return ret;
> > diff --git a/drivers/gpu/drm/bridge/tc358767.c
> > b/drivers/gpu/drm/bridge/tc358767.c
> > index da89922721ed..23a6f90b694b 100644
> > --- a/drivers/gpu/drm/bridge/tc358767.c
> > +++ b/drivers/gpu/drm/bridge/tc358767.c
> > @@ -1414,6 +1414,7 @@ static int tc_bridge_attach(struct drm_bridge *bridge,
> >         if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)
> >                 return 0;
> >  
> > +       tc->aux.drm_dev = drm;
> >         ret = drm_dp_aux_register(&tc->aux);
> >         if (ret < 0)
> >                 return ret;
> > diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > index 88df4dd0f39d..8e24272bbf00 100644
> > --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > @@ -362,6 +362,7 @@ static int ti_sn_bridge_attach(struct drm_bridge
> > *bridge,
> >                 return -EINVAL;
> >         }
> >  
> > +       pdata->aux.drm_dev = bridge->dev;
> >         ret = drm_dp_aux_register(&pdata->aux);
> >         if (ret < 0) {
> >                 drm_err(bridge->dev, "Failed to register DP AUX channel:
> > %d\n", ret);
> > diff --git a/drivers/gpu/drm/drm_dp_aux_dev.c
> > b/drivers/gpu/drm/drm_dp_aux_dev.c
> > index e25181bf2c48..06b374cae956 100644
> > --- a/drivers/gpu/drm/drm_dp_aux_dev.c
> > +++ b/drivers/gpu/drm/drm_dp_aux_dev.c
> > @@ -278,6 +278,12 @@ void drm_dp_aux_unregister_devnode(struct drm_dp_aux
> > *aux)
> >         if (!aux_dev) /* attach must have failed */
> >                 return;
> >  
> > +       /*
> > +        * As some AUX adapters may exist as platform devices which outlive
> > their respective DRM
> > +        * devices, we clear drm_dev to ensure that we never accidentally
> > reference a stale pointer
> > +        */
> > +       aux->drm_dev = NULL;
> > +
> >         mutex_lock(&aux_idr_mutex);
> >         idr_remove(&aux_idr, aux_dev->index);
> >         mutex_unlock(&aux_idr_mutex);
> > diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> > b/drivers/gpu/drm/drm_dp_mst_topology.c
> > index 932c4641ec3e..cf4f2f85711e 100644
> > --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> > +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> > @@ -2349,6 +2349,7 @@ drm_dp_mst_add_port(struct drm_device *dev,
> >         port->aux.is_remote = true;
> >  
> >         /* initialize the MST downstream port's AUX crc work queue */
> > +       port->aux.drm_dev = dev;
> >         drm_dp_remote_aux_init(&port->aux);
> >  
> >         /*
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c
> > b/drivers/gpu/drm/i915/display/intel_dp_aux.c
> > index eaebf123310a..0571c0794226 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
> > @@ -675,6 +675,7 @@ void intel_dp_aux_init(struct intel_dp *intel_dp)
> >         else
> >                 intel_dp->get_aux_send_ctl = g4x_get_aux_send_ctl;
> >  
> > +       intel_dp->aux.drm_dev = &dev_priv->drm;
> >         drm_dp_aux_init(&intel_dp->aux);
> >  
> >         /* Failure to allocate our preferred name is not critical */
> > diff --git a/drivers/gpu/drm/msm/edp/edp.h b/drivers/gpu/drm/msm/edp/edp.h
> > index eb34243dad53..8590f2ce274d 100644
> > --- a/drivers/gpu/drm/msm/edp/edp.h
> > +++ b/drivers/gpu/drm/msm/edp/edp.h
> > @@ -46,8 +46,7 @@ void edp_bridge_destroy(struct drm_bridge *bridge);
> >  struct drm_connector *msm_edp_connector_init(struct msm_edp *edp);
> >  
> >  /* AUX */
> > -void *msm_edp_aux_init(struct device *dev, void __iomem *regbase,
> > -                       struct drm_dp_aux **drm_aux);
> > +void *msm_edp_aux_init(struct msm_edp *edp, void __iomem *regbase, struct
> > drm_dp_aux **drm_aux);
> >  void msm_edp_aux_destroy(struct device *dev, struct edp_aux *aux);
> >  irqreturn_t msm_edp_aux_irq(struct edp_aux *aux, u32 isr);
> >  void msm_edp_aux_ctrl(struct edp_aux *aux, int enable);
> > diff --git a/drivers/gpu/drm/msm/edp/edp_aux.c
> > b/drivers/gpu/drm/msm/edp/edp_aux.c
> > index df10a0196d94..e3d85c622cfb 100644
> > --- a/drivers/gpu/drm/msm/edp/edp_aux.c
> > +++ b/drivers/gpu/drm/msm/edp/edp_aux.c
> > @@ -184,9 +184,9 @@ static ssize_t edp_aux_transfer(struct drm_dp_aux
> > *drm_aux,
> >         return ret;
> >  }
> >  
> > -void *msm_edp_aux_init(struct device *dev, void __iomem *regbase,
> > -       struct drm_dp_aux **drm_aux)
> > +void *msm_edp_aux_init(struct msm_edp *edp, void __iomem *regbase, struct
> > drm_dp_aux **drm_aux)
> >  {
> > +       struct device *dev = &edp->pdev->dev;
> >         struct edp_aux *aux = NULL;
> >         int ret;
> >  
> > @@ -201,6 +201,7 @@ void *msm_edp_aux_init(struct device *dev, void __iomem
> > *regbase,
> >  
> >         aux->drm_aux.name = "msm_edp_aux";
> >         aux->drm_aux.dev = dev;
> > +       aux->drm_aux.drm_dev = edp->dev;
> >         aux->drm_aux.transfer = edp_aux_transfer;
> >         ret = drm_dp_aux_register(&aux->drm_aux);
> >         if (ret) {
> > diff --git a/drivers/gpu/drm/msm/edp/edp_ctrl.c
> > b/drivers/gpu/drm/msm/edp/edp_ctrl.c
> > index 0d9657cc70db..57af3d8b6699 100644
> > --- a/drivers/gpu/drm/msm/edp/edp_ctrl.c
> > +++ b/drivers/gpu/drm/msm/edp/edp_ctrl.c
> > @@ -1153,7 +1153,7 @@ int msm_edp_ctrl_init(struct msm_edp *edp)
> >         }
> >  
> >         /* Init aux and phy */
> > -       ctrl->aux = msm_edp_aux_init(dev, ctrl->base, &ctrl->drm_aux);
> > +       ctrl->aux = msm_edp_aux_init(edp, ctrl->base, &ctrl->drm_aux);
> >         if (!ctrl->aux || !ctrl->drm_aux) {
> >                 pr_err("%s:failed to init aux\n", __func__);
> >                 return -ENOMEM;
> > diff --git a/drivers/gpu/drm/nouveau/nouveau_connector.c
> > b/drivers/gpu/drm/nouveau/nouveau_connector.c
> > index bfce762adcf0..d1b49508ecb9 100644
> > --- a/drivers/gpu/drm/nouveau/nouveau_connector.c
> > +++ b/drivers/gpu/drm/nouveau/nouveau_connector.c
> > @@ -1355,6 +1355,7 @@ nouveau_connector_create(struct drm_device *dev,
> >         case DRM_MODE_CONNECTOR_DisplayPort:
> >         case DRM_MODE_CONNECTOR_eDP:
> >                 nv_connector->aux.dev = connector->kdev;
> > +               nv_connector->aux.drm_dev = dev;
> >                 nv_connector->aux.transfer = nouveau_connector_aux_xfer;
> >                 snprintf(aux_name, sizeof(aux_name), "sor-%04x-%04x",
> >                          dcbe->hasht, dcbe->hashm);
> > diff --git a/drivers/gpu/drm/radeon/atombios_dp.c
> > b/drivers/gpu/drm/radeon/atombios_dp.c
> > index 15b00a347560..c50c504bad50 100644
> > --- a/drivers/gpu/drm/radeon/atombios_dp.c
> > +++ b/drivers/gpu/drm/radeon/atombios_dp.c
> > @@ -232,6 +232,7 @@ void radeon_dp_aux_init(struct radeon_connector
> > *radeon_connector)
> >  
> >         radeon_connector->ddc_bus->rec.hpd = radeon_connector->hpd.hpd;
> >         radeon_connector->ddc_bus->aux.dev = radeon_connector->base.kdev;
> > +       radeon_connector->ddc_bus->aux.drm_dev = radeon_connector->base.dev;
> >         if (ASIC_IS_DCE5(rdev)) {
> >                 if (radeon_auxch)
> >                         radeon_connector->ddc_bus->aux.transfer =
> > radeon_dp_aux_transfer_native;
> > diff --git a/drivers/gpu/drm/tegra/dpaux.c b/drivers/gpu/drm/tegra/dpaux.c
> > index ea56c6ec25e4..7d7cc90b6fc9 100644
> > --- a/drivers/gpu/drm/tegra/dpaux.c
> > +++ b/drivers/gpu/drm/tegra/dpaux.c
> > @@ -719,6 +719,7 @@ int drm_dp_aux_attach(struct drm_dp_aux *aux, struct
> > tegra_output *output)
> >         unsigned long timeout;
> >         int err;
> >  
> > +       aux->drm_dev = output->connector.dev;
> >         err = drm_dp_aux_register(aux);
> >         if (err < 0)
> >                 return err;
> > diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c
> > b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> > index 99158ee67d02..8272eee03adc 100644
> > --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
> > +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> > @@ -1069,6 +1069,7 @@ static int zynqmp_dp_aux_init(struct zynqmp_dp *dp)
> >  
> >         dp->aux.name = "ZynqMP DP AUX";
> >         dp->aux.dev = dp->dev;
> > +       dp->aux.drm_dev = dp->drm;
> >         dp->aux.transfer = zynqmp_dp_aux_transfer;
> >  
> >         return drm_dp_aux_register(&dp->aux);
> > diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> > index b35a1c1339e8..45ec74862212 100644
> > --- a/include/drm/drm_dp_helper.h
> > +++ b/include/drm/drm_dp_helper.h
> > @@ -1833,13 +1833,19 @@ struct drm_dp_aux_cec {
> >   * @name: user-visible name of this AUX channel and the I2C-over-AUX
> > adapter
> >   * @ddc: I2C adapter that can be used for I2C-over-AUX communication
> >   * @dev: pointer to struct device that is the parent for this AUX channel
> > + * @drm_dev: pointer to the &drm_device that owns this AUX channel. Beware,
> > this may be %NULL
> > + * before drm_dp_aux_register() has been called.
> >   * @crtc: backpointer to the crtc that is currently using this AUX channel
> >   * @hw_mutex: internal mutex used for locking transfers
> >   * @crc_work: worker that captures CRCs for each frame
> >   * @crc_count: counter of captured frame CRCs
> >   * @transfer: transfers a message representing a single AUX transaction
> >   *
> > - * The @dev field should be set to a pointer to the device that implements
> > the AUX channel.
> > + * The @dev field should be set to a pointer to the device that implements
> > the AUX channel. As well,
> > + * the @drm_dev field should be set to the &drm_device that will be using
> > this AUX channel as early
> > + * as possible. For many graphics drivers this should happen before
> > drm_dp_aux_init(), however it's
> > + * perfectly fine to set this field later so long as it's assigned before
> > calling
> > + * drm_dp_aux_register().
> >   *
> >   * The @name field may be used to specify the name of the I2C adapter. If
> > set to %NULL, dev_name()
> >   * of @dev will be used.
> > @@ -1866,6 +1872,7 @@ struct drm_dp_aux {
> >         const char *name;
> >         struct i2c_adapter ddc;
> >         struct device *dev;
> > +       struct drm_device *drm_dev;
> >         struct drm_crtc *crtc;
> >         struct mutex hw_mutex;
> >         struct work_struct crc_work;
> 

-- 
Sincerely,
   Lyude Paul (she/her)
   Software Engineer at Red Hat
   
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