Hi Maxime,

thanks for the ping on irc. I had accidently deleted v2 of this patch.

Sam

On Mon, Aug 30, 2021 at 11:49:09AM +0200, Maxime Ripard wrote:

The drm_helper_hpd_irq_event() function is iterating over all the connectors when an hotplug event is detected.

During that iteration, it will call each connector detect function and figure out if its status changed.

Finally, if any connector changed, it will notify the user-space and the clients that something changed on the DRM device.

This is supposed to be used for drivers that don't have a hotplug interrupt for individual connectors. However, drivers that can use an interrupt for a single connector are left in the dust and can either reimplement the logic used during the iteration for each connector or use that helper and iterate over all connectors all the time.

Since both are suboptimal, let's create a helper that will only perform the status detection on a single connector.

Signed-off-by: Maxime Ripard maxime@cerno.tech

A few comments in the following.

Sam

---

Changes from v1:

• Rename the shared function
• Move the hotplug event notification out of the shared function
• Added missing locks
• Improve the documentation
• Switched to drm_dbg_kms

---

drivers/gpu/drm/drm_probe_helper.c | 120 ++++++++++++++++++++--------- include/drm/drm_probe_helper.h | 1 + 2 files changed, 86 insertions(+), 35 deletions(-)

diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c index 5606bca3caa8..fcf32ec0b0c8 100644 --- a/drivers/gpu/drm/drm_probe_helper.c +++ b/drivers/gpu/drm/drm_probe_helper.c @@ -795,6 +795,86 @@ void drm_kms_helper_poll_fini(struct drm_device *dev) } EXPORT_SYMBOL(drm_kms_helper_poll_fini);

+static bool check_connector_changed(struct drm_connector *connector) +{

• struct drm_device *dev = connector->dev;
• enum drm_connector_status old_status;
• u64 old_epoch_counter;
• bool changed = false;
• /* Only handle HPD capable connectors. */
• drm_WARN_ON(dev, !(connector->polled & DRM_CONNECTOR_POLL_HPD));
• drm_WARN_ON(dev, !mutex_is_locked(&dev->mode_config.mutex));
• old_status = connector->status;
• old_epoch_counter = connector->epoch_counter;
• drm_dbg_kms(dev, "[CONNECTOR:%d:%s] Old epoch counter %llu\n",

•     connector->base.id,
  

•     connector->name,
  

•     old_epoch_counter);
  

• connector->status = drm_helper_probe_detect(connector, NULL, false);
• drm_dbg_kms(dev, "[CONNECTOR:%d:%s] status updated from %s to %s\n",

•     connector->base.id,
  

•     connector->name,
  

•     drm_get_connector_status_name(old_status),
  

•     drm_get_connector_status_name(connector->status));
  

• drm_dbg_kms(dev, "[CONNECTOR:%d:%s] New epoch counter %llu\n",

•     connector->base.id,
  

•     connector->name,
  

•     connector->epoch_counter);
  

• /*

• * Check if epoch counter had changed, meaning that we need
  

• * to send a uevent.
  

• */
  

• if (old_epoch_counter != connector->epoch_counter)

• changed = true;
  

If logging is included here we could do it like: if (old_epoch_counter != connector->epoch_counter) { drm_dbg_kms(dev, "[CONNECTOR:%d:%s] Changed epoch counter %llu => %llu\n", connector->base.id, connector->name, old_epoch_counter, connector->epoch_counter); return true; } else { drm_dbg_kms(dev, "[CONNECTOR:%d:%s] Same epoch counter %llu\n", connector->base.id, connector->name, connector->epoch_counter); return false; } }

So we only log epoch counter once. And the changed local variable is gone.

Just a suggestion.

• return changed;

+}

+/**

• • drm_connector_helper_hpd_irq_event - hotplug processing
• • @connector: drm_connector
• • Drivers can use this helper function to run a detect cycle on a connector
• • which has the DRM_CONNECTOR_POLL_HPD flag set in its &polled member.
• • This helper function is useful for drivers which can track hotplug
• • interrupts for a single connector. Drivers that want to send a
• • hotplug event for all connectors or can't track hotplug interrupts
• • per connector need to use drm_helper_hpd_irq_event().
• • This function must be called from process context with no mode
• • setting locks held.
• • Note that a connector can be both polled and probed from the hotplug
• • handler, in case the hotplug interrupt is known to be unreliable.

Documentation of the return value would be nice.

• */

+bool drm_connector_helper_hpd_irq_event(struct drm_connector *connector) +{

• struct drm_device *dev = connector->dev;
• bool changed;
• mutex_lock(&dev->mode_config.mutex);
• changed = check_connector_changed(connector);
• mutex_unlock(&dev->mode_config.mutex);
• if (changed) {

• drm_kms_helper_hotplug_event(dev);
  

• drm_dbg_kms(dev, "[CONNECTOR:%d:%s] Sent hotplug event\n",
  

• 	    connector->base.id,
  

• 	    connector->name);
  

• }
• return changed;

+} +EXPORT_SYMBOL(drm_connector_helper_hpd_irq_event);

/**

• drm_helper_hpd_irq_event - hotplug processing
• @dev: drm_device

@@ -808,9 +888,10 @@ EXPORT_SYMBOL(drm_kms_helper_poll_fini);

• interrupts for each connector.
• Drivers which support hotplug interrupts for each connector individually and

• • which have a more fine-grained detect logic should bypass this code and
• • directly call drm_kms_helper_hotplug_event() in case the connector state
• • changed.

• • which have a more fine-grained detect logic can use
• • drm_connector_helper_hpd_irq_event(). Alternatively, they should bypass this
• • code and directly call drm_kms_helper_hotplug_event() in case the connector
• • state changed.
  • This function must be called from process context with no mode
  • setting locks held.

Documentation of the return value would also be nice here. There are a few uses of the return value so we cannot just ignore it.

@@ -822,9 +903,7 @@ bool drm_helper_hpd_irq_event(struct drm_device *dev) { struct drm_connector *connector; struct drm_connector_list_iter conn_iter;

• enum drm_connector_status old_status; bool changed = false;

• u64 old_epoch_counter;

  if (!dev->mode_config.poll_enabled) return false;

@@ -832,37 +911,8 @@ bool drm_helper_hpd_irq_event(struct drm_device *dev) mutex_lock(&dev->mode_config.mutex); drm_connector_list_iter_begin(dev, &conn_iter); drm_for_each_connector_iter(connector, &conn_iter) {

• /* Only handle HPD capable connectors. */
  

• if (!(connector->polled & DRM_CONNECTOR_POLL_HPD))
  

• 	continue;
  

The old code skips connectors without DRM_CONNECTOR_POLL_HPD, where the new code will WARN is DRM_CONNECTOR_POLL_HPD is not set. This seems like a bigger change than what is intended.

• old_status = connector->status;
  

• old_epoch_counter = connector->epoch_counter;
  

• DRM_DEBUG_KMS("[CONNECTOR:%d:%s] Old epoch counter %llu\n", connector->base.id,
  

• 	      connector->name,
  

• 	      old_epoch_counter);
  

• connector->status = drm_helper_probe_detect(connector, NULL, false);
  

• DRM_DEBUG_KMS("[CONNECTOR:%d:%s] status updated from %s to %s\n",
  

• 	      connector->base.id,
  

• 	      connector->name,
  

• 	      drm_get_connector_status_name(old_status),
  

• 	      drm_get_connector_status_name(connector->status));
  

• DRM_DEBUG_KMS("[CONNECTOR:%d:%s] New epoch counter %llu\n",
  

• 	      connector->base.id,
  

• 	      connector->name,
  

• 	      connector->epoch_counter);
  

• /*
  

•  * Check if epoch counter had changed, meaning that we need
  

•  * to send a uevent.
  

•  */
  

• if (old_epoch_counter != connector->epoch_counter)
  

• if (check_connector_changed(connector))
  changed = true;
  

• } drm_connector_list_iter_end(&conn_iter); mutex_unlock(&dev->mode_config.mutex);

diff --git a/include/drm/drm_probe_helper.h b/include/drm/drm_probe_helper.h index 8d3ed2834d34..04c57564c397 100644 --- a/include/drm/drm_probe_helper.h +++ b/include/drm/drm_probe_helper.h @@ -18,6 +18,7 @@ int drm_helper_probe_detect(struct drm_connector *connector, void drm_kms_helper_poll_init(struct drm_device *dev); void drm_kms_helper_poll_fini(struct drm_device *dev); bool drm_helper_hpd_irq_event(struct drm_device *dev); +bool drm_connector_helper_hpd_irq_event(struct drm_connector *connector); void drm_kms_helper_hotplug_event(struct drm_device *dev);

void drm_kms_helper_poll_disable(struct drm_device *dev);

2.31.1