[PATCH v7 09/11] drm: uevent for connector status change

[Lyude Paul]

Hi-just wanted to give some general thoughts here.

First off I'm 100% behind the epoch idea, that was one of the ideas I had been
thinking of proposing here in the first place but probably forgot at some
point down the road.

A couple of other things:
 * I think it would also probably be good to have events for when connectors
   are added or removed from the system (mainly for MST)
 * Have we considered having any sort of SYNC event, like what evdev uses for
   signaling the end of a frame of events for input devices?

On Fri, 2019-05-10 at 14:12 +0200, Paul Kocialkowski wrote:
> Hi,
> 
> On Tue, 2019-05-07 at 21:57 +0530, Ramalingam C wrote:
> > DRM API for generating uevent for a status changes of connector's
> > property.
> > 
> > This uevent will have following details related to the status change:
> > 
> >   HOTPLUG=1, CONNECTOR=<connector_id> and PROPERTY=<property_id>
> > 
> > Need ACK from this uevent from userspace consumer.
> 
> So we just had some discussions over on IRC and at about the hotplug
> issue and came up with similar ideas:
> https://lists.freedesktop.org/archives/dri-devel/2019-May/217408.html
> 
> The conclusions of these discussions so far would be to have a more or
> less fine grain of uevent reporting depending on what happened. The
> point is that we need to cover different cases:
> - one or more properties changed;
> - the connector status changed;
> - something else about the connector changed (e.g. EDID/modes)
> 
> For the first case, we can send out:
> HOTPLUG=1
> CONNECTOR=<id>
> PROPERTY=<id>
> 
> and no reprobe is required.
> 
> For the second one, something like:
> HOTPLUG=1
> CONNECTOR=<id>
> STATUS=Connected/Disconnected
> 
> and a connector probe is needed for connected, but not for
> disconnected;
> 
> For the third one, we can only indicate the connector:
> HOTPLUG=1
> CONNECTOR=<id>
> 
> and a reprobe of the connector is always needed
> 
> Then we still have the legacy case:
> HOTPLUG=1
> 
> where userspace is expected to reprobe all the connectors.
> 
> I think this would deserve to be a separate series on its own. So I am
> proposing to take this one off your plate and come up with another
> seres implementing this proposal. What do you think?
> 
> Cheers,
> 
> Paul
> 
> > v2:
> >   Minor fixes at KDoc comments [Daniel]
> > v3:
> >   Check the property is really attached with connector [Daniel]
> > 
> > Signed-off-by: Ramalingam C <ramalingam.c at intel.com>
> > Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> > ---
> >  drivers/gpu/drm/drm_sysfs.c | 35 +++++++++++++++++++++++++++++++++++
> >  include/drm/drm_sysfs.h     |  5 ++++-
> >  2 files changed, 39 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
> > index 18b1ac442997..63fa951a20db 100644
> > --- a/drivers/gpu/drm/drm_sysfs.c
> > +++ b/drivers/gpu/drm/drm_sysfs.c
> > @@ -21,6 +21,7 @@
> >  #include <drm/drm_sysfs.h>
> >  #include <drm/drmP.h>
> >  #include "drm_internal.h"
> > +#include "drm_crtc_internal.h"
> >  
> >  #define to_drm_minor(d) dev_get_drvdata(d)
> >  #define to_drm_connector(d) dev_get_drvdata(d)
> > @@ -320,6 +321,9 @@ void drm_sysfs_lease_event(struct drm_device *dev)
> >   * Send a uevent for the DRM device specified by @dev.  Currently we only
> >   * set HOTPLUG=1 in the uevent environment, but this could be expanded to
> >   * deal with other types of events.
> > + *
> > + * Any new uapi should be using the drm_sysfs_connector_status_event()
> > + * for uevents on connector status change.
> >   */
> >  void drm_sysfs_hotplug_event(struct drm_device *dev)
> >  {
> > @@ -332,6 +336,37 @@ void drm_sysfs_hotplug_event(struct drm_device *dev)
> >  }
> >  EXPORT_SYMBOL(drm_sysfs_hotplug_event);
> >  
> > +/**
> > + * drm_sysfs_connector_status_event - generate a DRM uevent for connector
> > + * property status change
> > + * @connector: connector on which property status changed
> > + * @property: connector property whoes status changed.
> > + *
> > + * Send a uevent for the DRM device specified by @dev.  Currently we
> > + * set HOTPLUG=1 and connector id along with the attached property id
> > + * related to the status change.
> > + */
> > +void drm_sysfs_connector_status_event(struct drm_connector *connector,
> > +				      struct drm_property *property)
> > +{
> > +	struct drm_device *dev = connector->dev;
> > +	char hotplug_str[] = "HOTPLUG=1", conn_id[30], prop_id[30];
> > +	char *envp[4] = { hotplug_str, conn_id, prop_id, NULL };
> > +
> > +	WARN_ON(!drm_mode_obj_find_prop_id(&connector->base,
> > +					   property->base.id));
> > +
> > +	snprintf(conn_id, ARRAY_SIZE(conn_id),
> > +		 "CONNECTOR=%u", connector->base.id);
> > +	snprintf(prop_id, ARRAY_SIZE(prop_id),
> > +		 "PROPERTY=%u", property->base.id);
> > +
> > +	DRM_DEBUG("generating connector status event\n");
> > +
> > +	kobject_uevent_env(&dev->primary->kdev->kobj, KOBJ_CHANGE, envp);
> > +}
> > +EXPORT_SYMBOL(drm_sysfs_connector_status_event);
> > +
> >  static void drm_sysfs_release(struct device *dev)
> >  {
> >  	kfree(dev);
> > diff --git a/include/drm/drm_sysfs.h b/include/drm/drm_sysfs.h
> > index 4f311e836cdc..d454ef617b2c 100644
> > --- a/include/drm/drm_sysfs.h
> > +++ b/include/drm/drm_sysfs.h
> > @@ -4,10 +4,13 @@
> >  
> >  struct drm_device;
> >  struct device;
> > +struct drm_connector;
> > +struct drm_property;
> >  
> >  int drm_class_device_register(struct device *dev);
> >  void drm_class_device_unregister(struct device *dev);
> >  
> >  void drm_sysfs_hotplug_event(struct drm_device *dev);
> > -
> > +void drm_sysfs_connector_status_event(struct drm_connector *connector,
> > +				      struct drm_property *property);
> >  #endif
-- 
Cheers,
	Lyude Paul