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@xxxxxxxxxxxxxx> 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 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
