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

[Paul Kocialkowski]

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
-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com