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

From: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
To: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
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Subject: Re: [PATCH 1/6] drm/connector: report IRQ_HPD events to drm_connector_oob_hotplug_event()
Date: Thu, 16 Apr 2026 11:10:03 +0300	[thread overview]
Message-ID: <51b7c44e-36c9-461f-983a-eaa86eeb8cfd@ideasonboard.com> (raw)
In-Reply-To: <20260416-hpd-irq-events-v1-1-1ab1f1cfb2b2@oss.qualcomm.com>

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@oss.qualcomm.com>
> ---
>   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.

  Tomi

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