Re: [PATCH 1/5] drm/bridge: allow hpd_notify() to suppress connector hotplug events

[Dmitry Baryshkov]

On Tue, Aug 18, 2026 at 10:05:30AM +0800, Chaoyi Chen wrote:
> Hello Yongxing,
> 
> On 6/29/2026 10:48 PM, Yongxing Mou wrote:
> > The bridge connector framework currently invokes all bridge
> > hpd_notify() callbacks and unconditionally emits a connector hotplug
> > event afterwards.
> > 
> > However, not every HPD notification requires a userspace hotplug event.
> > 
> > In particular, DP MST bridges may use hpd_notify() to propagate HPD and
> > IRQ notifications through the bridge chain while the actual hotplug
> > handling is performed by the DRM DP MST core. Connector creation,
> > removal and userspace hotplug events are already managed by the MST
> > topology framework.
> > 
> > Allow hpd_notify() implementations to suppress the bridge connector
> > hotplug event by introducing a bool *send_hotplug parameter. Drivers
> > can clear this flag when HPD processing should not result in a
> > connector hotplug notification.
> > 
> > A NULL pointer indicates that hotplug suppression is not supported by
> > the caller, such as the connector detect polling path.
> >
> 
> Should we add an API to distinguish between regular HPD events and
> the IRQ-only notifications you mentioned?

It well might be so, rendering the first series listed as a dependency
as invalid (then it's good that we didn't land it up to now). I have
been torn between adding a new API and extending the HPD events. I
ended up choosing the latter one, but I might be wrong :-)

My idea was that both USB-C AltModes and native DP deliver both
mechanisms in the same way. If we add a separate API, we have to take
care of possible interactions between those two (i.e. how should we
react to IRQ_HPD, if we already have a HPD event being processed in
flight)?

> 
> I've recently seen similar approaches. For example, this patch[0] adds
> handling for internal events, which I think is somewhat similar to the
> IRQ-only notification here.
> 
> [0]: https://lore.kernel.org/all/20260806-synopsys-dw-dp-improvements-v11-11-0d508505f383@xxxxxxxxxxxxx/

Thanks for the reminder about this series. I need to review it.


-- 
With best wishes
Dmitry