Re: [PATCH 1/6] drm/connector: report IRQ_HPD events to drm_connector_oob_hotplug_event()

[Dmitry Baryshkov]

On Thu, Apr 16, 2026 at 11:10:03AM +0300, Tomi Valkeinen wrote:
> Hi,
> 
> On 16/04/2026 02:22, Dmitry Baryshkov wrote:
> > The DisplayPort standard defines a special kind of events called IRQ.
> > These events are used to notify DP Source about the events on the Sink
> > side. It is extremely important for DP MST handling, where the MST
> > events are reported through this IRQ.
> > 
> > In case of the USB-C DP AltMode there is no actual HPD pulse, but the
> > events are ported through the bits in the AltMode VDOs.
> > 
> > Extend the drm_connector_oob_hotplug_event() interface and report IRQ
> > events to the DisplayPort Sink drivers.
> > 
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/drm_connector.c          |  4 +++-
> >   drivers/usb/typec/altmodes/displayport.c | 12 ++++++++----
> >   include/drm/drm_connector.h              |  3 ++-
> >   3 files changed, 13 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> > index 47dc53c4a738..5fdacbd84bd7 100644
> > --- a/drivers/gpu/drm/drm_connector.c
> > +++ b/drivers/gpu/drm/drm_connector.c
> > @@ -3510,6 +3510,7 @@ struct drm_connector *drm_connector_find_by_fwnode(struct fwnode_handle *fwnode)
> >    * drm_connector_oob_hotplug_event - Report out-of-band hotplug event to connector
> >    * @connector_fwnode: fwnode_handle to report the event on
> >    * @status: hot plug detect logical state
> > + * @irq_hpd: HPD pulse detected
> >    *
> >    * On some hardware a hotplug event notification may come from outside the display
> >    * driver / device. An example of this is some USB Type-C setups where the hardware
> > @@ -3520,7 +3521,8 @@ struct drm_connector *drm_connector_find_by_fwnode(struct fwnode_handle *fwnode)
> >    * a drm_connector reference through calling drm_connector_find_by_fwnode().
> >    */
> >   void drm_connector_oob_hotplug_event(struct fwnode_handle *connector_fwnode,
> > -				     enum drm_connector_status status)
> > +				     enum drm_connector_status status,
> > +				     bool irq_hpd)
> I find the "IRQ HPD" naming always confusing, even if I'm somewhat familiar
> with DP, but if someone has mainly worked on HDMI, I'm sure it's even worse.
> 
> Can we define this a bit more precisely? Is 'irq_hpd' only for displayport?
> If so, perhaps 'dp_irq_hpd' or 'displayport_irq_hpd'. I might even call it
> 'dp_hpd_pulse', but maybe that's not good as the spec talks about HPD pulse
> for both short and long ones (although in the kernel doc you just write "HPD
> pulse")... The kernel doc could be expanded a bit to make it clear what this
> flag indicates.

I attempted to stay away from defining a DP-specific flag, keeping it
generic enough. HDMI is pretty close (IMO) to requiring separate flag in
Linux. Likewise I'd rather not use "pulse". The DP AltMode defines a bit
in the VDO rather than a pulse.

Anyway, if irq_hpd doesn't sound precise enough, what about "bool
extra_irq"? This would convey that this is the extra hpd-related IRQ,
but it would also be obvious that it's not related to the HPD pin
itself.


-- 
With best wishes
Dmitry