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Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge.

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Hi Archit,

On Tuesday 20 Jun 2017 09:18:00 Archit Taneja wrote:
> On 06/16/2017 08:13 PM, Eric Anholt wrote:
> > Archit Taneja <architt@codeaurora.org> writes:
> >> On 06/16/2017 02:11 AM, Eric Anholt wrote:
> >>> If the panel-bridge is being set up after the drm_mode_config_reset(),
> >>> then the connector's state would never get initialized, and we'd
> >>> dereference the NULL in the hotplug path.  We also need to register
> >>> the connector, so that userspace can get at it.
> >> 
> >> Shouldn't the KMS driver make sure the panel-bridge is set up before
> >> drm_mode_config_reset? Is it the case when we're inserting the
> >> panel-bridge driver as a module?
> >> 
> >> 
> >> All the connectors that have been added are registered automatically
> >> when drm_dev_register() is called by the KMS driver. Registering a
> >> connector in the middle of setting up our driver is prone to race
> >> conditions if the userspace decides to use them immediately.
> > 
> > Yeah, this is fixing initializing panel_bridge at DSI host_attach time,
> > which in the case of a panel module that creates the DSI device
> > (adv7533-style, like you said I should use as a reference) will be after
> > drm_mode_config_reset() and drm_dev_register().
> 
> Okay. In the case of the msm kms driver, we defer probe until the
> adv7533 module is inserted, only then we proceed to drm_mode_config_reset()
> and drm_dev_register(). I assumed this was the general practice followed by
> most kms drivers. I.,e the kms driver defers probe until all connector
> related modules are inserted, and only then proceed to create a drm device.

I'd love to see support for a more dynamic approach that would allow 
registering outputs at runtime. Until that's implemented, however, I agree 
with your statement, drivers should wait until all components are available 
before registering the DRM device.

> Feedback from others on this would be appreciated, though.

-- 
Regards,

Laurent Pinchart

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Thread

[PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Eric Anholt <eric@anholt.net> - 2017-06-15 22:50 +0200
  Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Archit Taneja <architt@codeaurora.org> - 2017-06-16 07:50 +0200
    Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Eric Anholt <eric@anholt.net> - 2017-06-16 16:50 +0200
      Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Archit Taneja <architt@codeaurora.org> - 2017-06-20 05:50 +0200
        Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Laurent Pinchart <laurent.pinchart@ideasonboard.com> - 2017-06-20 09:40 +0200
        Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Eric Anholt <eric@anholt.net> - 2017-06-20 19:40 +0200
          Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Benjamin Gaignard <benjamin.gaignard@linaro.org> - 2017-06-22 10:00 +0200
            Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Archit Taneja <architt@codeaurora.org> - 2017-06-22 10:20 +0200
              Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-06-22 11:30 +0200
                Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Andrzej Hajda <a.hajda@samsung.com> - 2017-06-22 14:30 +0200
                Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-06-22 14:50 +0200
                Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Andrzej Hajda <a.hajda@samsung.com> - 2017-06-22 15:20 +0200
                Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-06-22 15:40 +0200
                Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Andrzej Hajda <a.hajda@samsung.com> - 2017-06-23 09:30 +0200
                Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Boris Brezillon <boris.brezillon@free-electrons.com> - 2017-06-23 09:40 +0200
                Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Archit Taneja <architt@codeaurora.org> - 2017-06-23 16:00 +0200
                Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Eric Anholt <eric@anholt.net> - 2017-06-24 00:00 +0200
                Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Archit Taneja <architt@codeaurora.org> - 2017-06-27 09:00 +0200
              Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Philippe CORNU <philippe.cornu@st.com> - 2017-06-22 11:40 +0200
              Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Eric Anholt <eric@anholt.net> - 2017-06-23 23:40 +0200
  Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge. Daniel Vetter <daniel@ffwll.ch> - 2017-06-23 11:10 +0200

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