On Tue, Aug 29, 2023 at 05:30:59AM +0000, Brandon Pollack wrote: > This change adds the ability to read or write a "1" or a "0" to the > newly added "connected" attribute of a connector in the vkms entry in > configfs. > > A write will trigger a call to drm_kms_helper_hotplug_event, causing a > hotplug uevent. > > With this we can write virtualized multidisplay tests that involve > hotplugging displays (eg recompositing windows when a monitor is turned > off). > > Signed-off-by: Brandon Pollack <brpol@xxxxxxxxxxxx> > --- > Documentation/gpu/vkms.rst | 2 +- > drivers/gpu/drm/vkms/vkms_configfs.c | 68 ++++++++++++++++++++++++++-- > drivers/gpu/drm/vkms/vkms_drv.h | 11 +++++ > drivers/gpu/drm/vkms/vkms_output.c | 47 ++++++++++++++++++- > 4 files changed, 123 insertions(+), 5 deletions(-) > > diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst > index c3875bf66dba..7f715097539c 100644 > --- a/Documentation/gpu/vkms.rst > +++ b/Documentation/gpu/vkms.rst > @@ -145,7 +145,7 @@ We want to be able to manipulate vkms instances without having to reload the > module. Such configuration can be added as extensions to vkms's ConfigFS > support. Use-cases: > > -- Hotplug/hotremove connectors on the fly (to be able to test DP MST handling > +- Hotremove connectors on the fly (to be able to test DP MST handling > of compositors). > > - Change output configuration: Plug/unplug screens, change EDID, allow changing > diff --git a/drivers/gpu/drm/vkms/vkms_configfs.c b/drivers/gpu/drm/vkms/vkms_configfs.c > index bc35dcc47585..d231e28101ae 100644 > --- a/drivers/gpu/drm/vkms/vkms_configfs.c > +++ b/drivers/gpu/drm/vkms/vkms_configfs.c > @@ -1,5 +1,6 @@ > // SPDX-License-Identifier: GPL-2.0+ > > +#include "drm/drm_probe_helper.h" > #include <linux/configfs.h> > #include <linux/mutex.h> > #include <linux/platform_device.h> > @@ -40,6 +41,7 @@ > * `-- vkms > * `-- test > * |-- connectors > + * `-- connected > * |-- crtcs > * |-- encoders > * |-- planes > @@ -89,6 +91,14 @@ > * > * echo 1 > /config/vkms/test/enabled > * > + * By default no display is "connected" so to connect a connector you'll also > + * have to write 1 to a connectors "connected" attribute:: > + * > + * echo 1 > /config/vkms/test/connectors/connector/connected I think it'd be really good if we allow all connector status values, including unknown. It's not very common, which is why most compositors utterly fail at handling it in a reasonable way. > + * > + * One can verify that this is worked using the `modetest` utility or the > + * equivalent for your platform. > + * > * When you're done with the virtual device, you can clean up the device like > * so:: > * > @@ -236,7 +246,58 @@ static void add_possible_encoders(struct config_group *parent, > > /* Connector item, e.g. /config/vkms/device/connectors/ID */ > > +static ssize_t connector_connected_show(struct config_item *item, char *buf) > +{ > + struct vkms_config_connector *connector = > + item_to_config_connector(item); > + struct vkms_configfs *configfs = connector_item_to_configfs(item); > + bool connected = false; > + > + mutex_lock(&configfs->lock); > + connected = connector->connected; > + mutex_unlock(&configfs->lock); > + > + return sprintf(buf, "%d\n", connected); > +} > + > +static ssize_t connector_connected_store(struct config_item *item, > + const char *buf, size_t len) > +{ > + struct vkms_config_connector *connector = > + item_to_config_connector(item); > + struct vkms_configfs *configfs = connector_item_to_configfs(item); > + int val, ret; > + > + ret = kstrtouint(buf, 10, &val); > + if (ret) > + return ret; > + > + if (val != 1 && val != 0) > + return -EINVAL; > + > + mutex_lock(&configfs->lock); > + connector->connected = val; > + if (!connector->connector) { > + pr_info("VKMS Device %s is not yet enabled, connector will be enabled on start", > + configfs->device_group.cg_item.ci_name); > + } > + mutex_unlock(&configfs->lock); > + > + if (connector->connector) > + drm_kms_helper_hotplug_event(connector->connector->dev); Ok a few lifetime bugs here: - Calling drm_kms_helper_hotplug_event after you unluck means all the drm stuff might have disappeared meanwhile. Oops. - It is worse, because switching to configfs_subsystem.su_mutex will not prevent the race, because the vkms_device can disappear independently (by manually unbinding the driver in sysfs) at least with the real platform driver approach. This is another reason why I'm not sure having a real platform driver with probe/remove hooks is a good idea. - Furthermore the drm_connector might also disappear. I think the way to properly fix this is: - configfs needs to hold a reference of it's on to the drm_device in vkms_device. - it needs to call a vkms function to update the connector hotplug status with only the configfs obj idx. That function then needs to find the right drm_connector using the drm_connector_iter functions (which will sort out any lifetime/locking issues) until is has the right one, and then update the connector status. No matter what, we cannot have a backpointer from any drm object to configfs, that doesn't work correctly. -Sima > + > + return len; > +} > + > +CONFIGFS_ATTR(connector_, connected); > + > +static struct configfs_attribute *connector_attrs[] = { > + &connector_attr_connected, > + NULL, > +}; > + > static struct config_item_type connector_type = { > + .ct_attrs = connector_attrs, > .ct_owner = THIS_MODULE, > }; > > @@ -264,7 +325,7 @@ static ssize_t plane_type_show(struct config_item *item, char *buf) > plane_type = plane->type; > mutex_unlock(&configfs->lock); > > - return sprintf(buf, "%u", plane_type); > + return sprintf(buf, "%u\n", plane_type); > } > > static ssize_t plane_type_store(struct config_item *item, const char *buf, > @@ -319,6 +380,7 @@ static struct config_group *connectors_group_make(struct config_group *group, > &connector_type); > add_possible_encoders(&connector->config_group, > &connector->possible_encoders.group); > + connector->connected = false; > > return &connector->config_group; > } > @@ -500,7 +562,7 @@ static ssize_t device_enabled_show(struct config_item *item, char *buf) > is_enabled = configfs->vkms_device != NULL; > mutex_unlock(&configfs->lock); > > - return sprintf(buf, "%d", is_enabled); > + return sprintf(buf, "%d\n", is_enabled); > } > > static ssize_t device_enabled_store(struct config_item *item, const char *buf, > @@ -557,7 +619,7 @@ static ssize_t device_id_show(struct config_item *item, char *buf) > > mutex_unlock(&configfs->lock); > > - return sprintf(buf, "%d", id); > + return sprintf(buf, "%d\n", id); > } > > CONFIGFS_ATTR_RO(device_, id); > diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h > index 2b9545ada9c2..5336281f397e 100644 > --- a/drivers/gpu/drm/vkms/vkms_drv.h > +++ b/drivers/gpu/drm/vkms/vkms_drv.h > @@ -3,6 +3,7 @@ > #ifndef _VKMS_DRV_H_ > #define _VKMS_DRV_H_ > > +#include "drm/drm_connector.h" > #include <linux/configfs.h> > #include <linux/hrtimer.h> > > @@ -147,7 +148,9 @@ struct vkms_config_links { > > struct vkms_config_connector { > struct config_group config_group; > + struct drm_connector *connector; > struct vkms_config_links possible_encoders; > + bool connected; > }; > > struct vkms_config_crtc { > @@ -220,6 +223,10 @@ struct vkms_device { > #define item_to_configfs(item) \ > container_of(to_config_group(item), struct vkms_configfs, device_group) > > +#define connector_item_to_configfs(item) \ > + container_of(to_config_group(item->ci_parent), struct vkms_configfs, \ > + connectors_group) > + > #define item_to_config_connector(item) \ > container_of(to_config_group(item), struct vkms_config_connector, \ > config_group) > @@ -279,4 +286,8 @@ int vkms_enable_writeback_connector(struct vkms_device *vkmsdev, > int vkms_init_configfs(void); > void vkms_unregister_configfs(void); > > +/* Connector hotplugging */ > +enum drm_connector_status vkms_connector_detect(struct drm_connector *connector, > + bool force); > + > #endif /* _VKMS_DRV_H_ */ > diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c > index 0ee1f3f4a305..1a1cd0202c5f 100644 > --- a/drivers/gpu/drm/vkms/vkms_output.c > +++ b/drivers/gpu/drm/vkms/vkms_output.c > @@ -1,5 +1,6 @@ > // SPDX-License-Identifier: GPL-2.0+ > > +#include <drm/drm_print.h> > #include <drm/drm_atomic_helper.h> > #include <drm/drm_connector.h> > #include <drm/drm_crtc.h> > @@ -8,10 +9,12 @@ > #include <drm/drm_plane.h> > #include <drm/drm_probe_helper.h> > #include <drm/drm_simple_kms_helper.h> > +#include <linux/printk.h> > > #include "vkms_drv.h" > > static const struct drm_connector_funcs vkms_connector_funcs = { > + .detect = vkms_connector_detect, > .fill_modes = drm_helper_probe_single_connector_modes, > .destroy = drm_connector_cleanup, > .reset = drm_atomic_helper_connector_reset, > @@ -19,6 +22,48 @@ static const struct drm_connector_funcs vkms_connector_funcs = { > .atomic_destroy_state = drm_atomic_helper_connector_destroy_state, > }; > > +static const struct vkms_config_connector * > +find_config_for_connector(struct drm_connector *connector) > +{ > + struct vkms_device *vkms = drm_device_to_vkms_device(connector->dev); > + struct vkms_configfs *configfs = vkms->configfs; > + struct config_item *item; > + > + if (!configfs) { > + pr_info("Default connector has no configfs entry"); > + return NULL; > + } > + > + list_for_each_entry(item, &configfs->connectors_group.cg_children, > + ci_entry) { > + struct vkms_config_connector *config_connector = > + item_to_config_connector(item); > + if (config_connector->connector == connector) > + return config_connector; > + } > + > + pr_warn("Could not find config to match connector %s, but configfs was initialized", > + connector->name); > + > + return NULL; > +} > + > +enum drm_connector_status vkms_connector_detect(struct drm_connector *connector, > + bool force) > +{ > + enum drm_connector_status status = connector_status_connected; > + const struct vkms_config_connector *config_connector = > + find_config_for_connector(connector); > + > + if (!config_connector) > + return connector_status_connected; > + > + if (!config_connector->connected) > + status = connector_status_disconnected; > + > + return status; > +} > + > static const struct drm_encoder_funcs vkms_encoder_funcs = { > .destroy = drm_encoder_cleanup, > }; > @@ -280,12 +325,12 @@ int vkms_output_init(struct vkms_device *vkmsdev) > struct vkms_config_connector *config_connector = > item_to_config_connector(item); > struct drm_connector *connector = vkms_connector_init(vkmsdev); > - > if (IS_ERR(connector)) { > DRM_ERROR("Failed to init connector from config: %s", > item->ci_name); > return PTR_ERR(connector); > } > + config_connector->connector = connector; > > for (int j = 0; j < output->num_encoders; j++) { > struct encoder_map *encoder = &encoder_map[j]; > -- > 2.42.0.rc2.253.gd59a3bf2b4-goog > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch