Re: [PATCH v2 5/6] drm/vkms: Support enabling ConfigFS devices

[Brandon Ross Pollack <brpol@xxxxxxxxxxxx>]

On 8/15/23 23:01, Marius Vlad wrote:
> Hi,
>
> See below some minor comments:
>
> On Fri, Jun 23, 2023 at 06:23:47PM -0400, Jim Shargo wrote:
> > VKMS now supports creating and using virtual devices!
> >
> > In addition to the enabling logic, this commit also prevents users from
> > adding new objects once a card is registered.
> >
> > Signed-off-by: Jim Shargo <jshargo@xxxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/vkms/vkms_configfs.c |  37 +++--
> >   drivers/gpu/drm/vkms/vkms_crtc.c     |   4 +-
> >   drivers/gpu/drm/vkms/vkms_drv.c      |   3 +-
> >   drivers/gpu/drm/vkms/vkms_drv.h      |   2 +-
> >   drivers/gpu/drm/vkms/vkms_output.c   | 201 +++++++++++++++++++++++----
> >   5 files changed, 202 insertions(+), 45 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/vkms/vkms_configfs.c b/drivers/gpu/drm/vkms/vkms_configfs.c
> > index 544024735d19..f5eed6d23dcd 100644
> > --- a/drivers/gpu/drm/vkms/vkms_configfs.c
> > +++ b/drivers/gpu/drm/vkms/vkms_configfs.c
> > @@ -504,29 +504,40 @@ static ssize_t device_enabled_store(struct config_item *item, const char *buf,
> >   {
> >   	struct vkms_configfs *configfs = item_to_configfs(item);
> >   	struct vkms_device *device;
> > -	int value, ret;
> > +	int enabled, ret;
> >   
> > -	ret = kstrtoint(buf, 0, &value);
> > +	ret = kstrtoint(buf, 0, &enabled);
> >   	if (ret)
> >   		return ret;
> >   
> > -	if (value != 1)
> > -		return -EINVAL;
> > -
> > -	mutex_lock(&configfs->lock);
> > -
> > -	if (configfs->vkms_device) {
> > +	if (enabled == 0) {
> > +		mutex_lock(&configfs->lock);
> > +		if (configfs->vkms_device) {
> > +			vkms_remove_device(configfs->vkms_device);
> > +			configfs->vkms_device = NULL;
> > +		}
> >   		mutex_unlock(&configfs->lock);
> > +
> >   		return len;
> >   	}
> >   
> > -	device = vkms_add_device(configfs);
> > -	mutex_unlock(&configfs->lock);
> > +	if (enabled == 1) {
> > +		mutex_lock(&configfs->lock);
> > +		if (!configfs->vkms_device) {
> > +			device = vkms_add_device(configfs);
> > +			if (IS_ERR(device)) {
> > +				mutex_unlock(&configfs->lock);
> > +				return -PTR_ERR(device);
> > +			}
> > +
> > +			configfs->vkms_device = device;
> > +		}
> > +		mutex_unlock(&configfs->lock);
> >   
> > -	if (IS_ERR(device))
> > -		return -PTR_ERR(device);
> > +		return len;
> > +	}
> >   
> > -	return len;
> > +	return -EINVAL;
> >   }
> >   
> >   CONFIGFS_ATTR(device_, enabled);
> > diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c
> > index d91e49c53adc..5ebb5264f6ef 100644
> > --- a/drivers/gpu/drm/vkms/vkms_crtc.c
> > +++ b/drivers/gpu/drm/vkms/vkms_crtc.c
> > @@ -278,7 +278,7 @@ static const struct drm_crtc_helper_funcs vkms_crtc_helper_funcs = {
> >   
> >   struct vkms_crtc *vkms_crtc_init(struct vkms_device *vkmsdev,
> >   				 struct drm_plane *primary,
> > -				 struct drm_plane *cursor)
> > +				 struct drm_plane *cursor, const char *name)
> >   {
> >   	struct drm_device *dev = &vkmsdev->drm;
> >   	struct vkms_crtc *vkms_crtc;
> > @@ -290,7 +290,7 @@ struct vkms_crtc *vkms_crtc_init(struct vkms_device *vkmsdev,
> >   	vkms_crtc = &vkmsdev->output.crtcs[vkmsdev->output.num_crtcs++];
> >   
> >   	ret = drmm_crtc_init_with_planes(dev, &vkms_crtc->base, primary, cursor,
> > -					 &vkms_crtc_funcs, NULL);
> > +					 &vkms_crtc_funcs, name);
> >   	if (ret) {
> >   		DRM_ERROR("Failed to init CRTC\n");
> >   		goto out_error;
> > diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
> > index 1b5b7143792f..314a04659c5f 100644
> > --- a/drivers/gpu/drm/vkms/vkms_drv.c
> > +++ b/drivers/gpu/drm/vkms/vkms_drv.c
> > @@ -210,7 +210,7 @@ static int vkms_platform_probe(struct platform_device *pdev)
> >   	ret = drm_dev_register(&vkms_device->drm, 0);
> >   	if (ret) {
> >   		DRM_ERROR("Unable to register device with id %d\n", pdev->id);
> > -		return ret;
> > +		goto out_release_group;
> >   	}
> >   
> >   	drm_fbdev_generic_setup(&vkms_device->drm, 0);
> > @@ -256,6 +256,7 @@ struct vkms_device *vkms_add_device(struct vkms_configfs *configfs)
> >   			dev, &vkms_platform_driver.driver))) {
> >   		pdev = to_platform_device(dev);
> >   		max_id = max(max_id, pdev->id);
> > +		put_device(dev);
> >   	}
> >   
> >   	pdev = platform_device_register_data(NULL, DRIVER_NAME, max_id + 1,
> > diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> > index 3634eeeb4548..3d592d085f49 100644
> > --- a/drivers/gpu/drm/vkms/vkms_drv.h
> > +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> > @@ -239,7 +239,7 @@ void vkms_remove_device(struct vkms_device *vkms_device);
> >   /* CRTC */
> >   struct vkms_crtc *vkms_crtc_init(struct vkms_device *vkmsdev,
> >   				 struct drm_plane *primary,
> > -				 struct drm_plane *cursor);
> > +				 struct drm_plane *cursor, const char *name);
> >   
> >   int vkms_output_init(struct vkms_device *vkmsdev);
> >   int vkms_output_init_default(struct vkms_device *vkmsdev);
> > diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c
> > index c9e6c653de19..806ff01954ad 100644
> > --- a/drivers/gpu/drm/vkms/vkms_output.c
> > +++ b/drivers/gpu/drm/vkms/vkms_output.c
> > @@ -2,8 +2,10 @@
> >   
> >   #include <drm/drm_atomic_helper.h>
> >   #include <drm/drm_connector.h>
> > +#include <drm/drm_crtc.h>
> >   #include <drm/drm_edid.h>
> >   #include <drm/drm_encoder.h>
> > +#include <drm/drm_plane.h>
> >   #include <drm/drm_probe_helper.h>
> >   #include <drm/drm_simple_kms_helper.h>
> >   
> > @@ -82,7 +84,6 @@ static struct drm_encoder *vkms_encoder_init(struct vkms_device *vkms_device)
> >   
> >   int vkms_output_init_default(struct vkms_device *vkmsdev)
> >   {
> > -	struct vkms_output *output = &vkmsdev->output;
> >   	struct drm_device *dev = &vkmsdev->drm;
> >   	struct drm_connector *connector;
> >   	struct drm_encoder *encoder;
> > @@ -101,8 +102,7 @@ int vkms_output_init_default(struct vkms_device *vkmsdev)
> >   			struct vkms_plane *overlay = vkms_plane_init(
> >   				vkmsdev, DRM_PLANE_TYPE_OVERLAY);
> >   			if (IS_ERR(overlay)) {
> > -				ret = PTR_ERR(overlay);
> > -				goto err_planes;
> > +				return PTR_ERR(overlay);
> >   			}
> >   		}
> >   	}
> > @@ -110,17 +110,16 @@ int vkms_output_init_default(struct vkms_device *vkmsdev)
> >   	if (vkmsdev->config.cursor) {
> >   		cursor = vkms_plane_init(vkmsdev, DRM_PLANE_TYPE_CURSOR);
> >   		if (IS_ERR(cursor)) {
> > -			ret = PTR_ERR(cursor);
> > -			goto err_planes;
> > +			return PTR_ERR(cursor);
> >   		}
> >   	}
> >   
> >   	vkms_crtc = vkms_crtc_init(vkmsdev, &primary->base,
> > -				   cursor ? &cursor->base : NULL);
> > +				   cursor ? &cursor->base : NULL,
> > +				   "crtc-default");
> >   	if (IS_ERR(vkms_crtc)) {
> >   		DRM_ERROR("Failed to init crtc\n");
> > -		ret = PTR_ERR(vkms_crtc);
> > -		goto err_planes;
> > +		return PTR_ERR(vkms_crtc);
> >   	}
> >   
> >   	for (int i = 0; i < vkmsdev->output.num_planes; i++) {
> > @@ -131,22 +130,20 @@ int vkms_output_init_default(struct vkms_device *vkmsdev)
> >   	connector = vkms_connector_init(vkmsdev);
> >   	if (IS_ERR(connector)) {
> >   		DRM_ERROR("Failed to init connector\n");
> > -		ret = PTR_ERR(connector);
> > -		goto err_connector;
> > +		return PTR_ERR(connector);
> >   	}
> >   
> >   	encoder = vkms_encoder_init(vkmsdev);
> >   	if (IS_ERR(encoder)) {
> >   		DRM_ERROR("Failed to init encoder\n");
> > -		ret = PTR_ERR(encoder);
> > -		goto err_encoder;
> > +		return PTR_ERR(encoder);
> >   	}
> >   	encoder->possible_crtcs |= drm_crtc_mask(&vkms_crtc->base);
> >   
> >   	ret = drm_connector_attach_encoder(connector, encoder);
> >   	if (ret) {
> >   		DRM_ERROR("Failed to attach connector to encoder\n");
> > -		goto err_attach;
> > +		return ret;
> >   	}
> >   
> >   	if (vkmsdev->config.writeback) {
> > @@ -158,27 +155,175 @@ int vkms_output_init_default(struct vkms_device *vkmsdev)
> >   	drm_mode_config_reset(dev);
> >   
> >   	return 0;
> > +}
> >   
> > -err_attach:
> > -	drm_encoder_cleanup(encoder);
> > +static bool is_object_linked(struct vkms_config_links *links, unsigned long idx)
> > +{
> > +	return links->linked_object_bitmap & (1 << idx);
> > +}
> >   
> > -err_encoder:
> > -	drm_connector_cleanup(connector);
> > +int vkms_output_init(struct vkms_device *vkmsdev)
> > +{
> > +	struct drm_device *dev = &vkmsdev->drm;
> > +	struct vkms_configfs *configfs = vkmsdev->configfs;
> > +	struct vkms_output *output = &vkmsdev->output;
> > +	struct plane_map {
> > +		struct vkms_config_plane *config_plane;
> > +		struct vkms_plane *plane;
> > +	} plane_map[VKMS_MAX_PLANES] = { 0 };
> > +	struct encoder_map {
> > +		struct vkms_config_encoder *config_encoder;
> > +		struct drm_encoder *encoder;
> > +	} encoder_map[VKMS_MAX_OUTPUT_OBJECTS] = { 0 };
> > +	struct config_item *item;
> > +	int map_idx = 0;
> > +
> > +	list_for_each_entry(item, &configfs->planes_group.cg_children,
> > +			    ci_entry) {
> > +		struct vkms_config_plane *config_plane =
> > +			item_to_config_plane(item);
> > +		struct vkms_plane *plane =
> > +			vkms_plane_init(vkmsdev, config_plane->type);
> > +
> > +		if (IS_ERR(plane)) {
> > +			DRM_ERROR("Unable to init plane from config: %s",
> > +				  item->ci_name);
> > +			return PTR_ERR(plane);
> > +		}
> >   
> > -err_connector:
> > -	drm_crtc_cleanup(&vkms_crtc->base);
> > +		plane_map[map_idx].config_plane = config_plane;
> > +		plane_map[map_idx].plane = plane;
> > +		map_idx += 1;
> > +	}
> >   
> > -err_planes:
> > -	for (int i = 0; i < output->num_planes; i++) {
> > -		drm_plane_cleanup(&output->planes[i].base);
> > +	map_idx = 0;
> > +	list_for_each_entry(item, &configfs->encoders_group.cg_children,
> > +			    ci_entry) {
> > +		struct vkms_config_encoder *config_encoder =
> > +			item_to_config_encoder(item);
> > +		struct drm_encoder *encoder = vkms_encoder_init(vkmsdev);
> > +
> > +		if (IS_ERR(encoder)) {
> > +			DRM_ERROR("Failed to init config encoder: %s",
> > +				  item->ci_name);
> > +			return PTR_ERR(encoder);
> > +		}
> > +		encoder_map[map_idx].config_encoder = config_encoder;
> A two connector configuration without an encoder would have the
> potential of blowing up if we don't create a second_encoder.

What a catch!!! I tested this and sure enough BOOM!

Switched to limiting based on output->num_encoders as it should be.

> > +		encoder_map[map_idx].encoder = encoder;
> > +		map_idx += 1;
> >   	}
> >   
> > -	memset(output, 0, sizeof(*output));
> > +	list_for_each_entry(item, &configfs->connectors_group.cg_children,
> > +			    ci_entry) {
> > +		struct vkms_config_connector *config_connector =
> > +			item_to_config_connector(item);
> > +		struct drm_connector *connector = vkms_connector_init(vkmsdev);
> >   
> > -	return ret;
> > -}
> > +		if (IS_ERR(connector)) {
> > +			DRM_ERROR("Failed to init connector from config: %s",
> > +				  item->ci_name);
> > +			return PTR_ERR(connector);
> > +		}
> >   
> > -int vkms_output_init(struct vkms_device *vkmsdev)
> > -{
> > -	return -ENOTSUPP;
> > +		for (int j = 0; j < output->num_connectors; j++) {
> > +			struct encoder_map *encoder = &encoder_map[j];
> > +
> > +			if (is_object_linked(
> > +				    &config_connector->possible_encoders,
> > +				    encoder->config_encoder
> > +					    ->encoder_config_idx)) {
> Here encoder->config_encoder for two connectors but a single encoder
> will give back a empty encoder.
> > +				drm_connector_attach_encoder(connector,
> > +							     encoder->encoder);
> > +			}
> > +		}
> > +	}
> > +
> > +	list_for_each_entry(item, &configfs->crtcs_group.cg_children,
> > +			    ci_entry) {
> > +		struct vkms_config_crtc *config_crtc =
> > +			item_to_config_crtc(item);
> > +		struct vkms_crtc *vkms_crtc;
> > +		struct drm_plane *primary = NULL, *cursor = NULL;
> > +
> > +		for (int j = 0; j < output->num_planes; j++) {
> > +			struct plane_map *plane_entry = &plane_map[j];
> > +			struct drm_plane *plane = &plane_entry->plane->base;
> > +
> > +			if (!is_object_linked(
> > +				    &plane_entry->config_plane->possible_crtcs,
> > +				    config_crtc->crtc_config_idx)) {
> > +				continue;
> > +			}
> > +
> > +			if (plane->type == DRM_PLANE_TYPE_PRIMARY) {
> > +				if (primary) {
> > +					DRM_WARN(
> > +						"Too many primary planes found for crtc %s.",
> > +						item->ci_name);
> > +					return EINVAL;
> > +				}
> > +				primary = plane;
> > +			} else if (plane->type == DRM_PLANE_TYPE_CURSOR) {
> > +				if (cursor) {
> > +					DRM_WARN(
> > +						"Too many cursor planes found for crtc %s.",
> > +						item->ci_name);
> > +					return EINVAL;
> > +				}
> > +				cursor = plane;
> > +			}
> > +		}
> > +
> > +		if (!primary) {
> > +			DRM_WARN("No primary plane configured for crtc %s",
> > +				 item->ci_name);
> > +			return EINVAL;
> > +		}
> > +
> > +		vkms_crtc =
> > +			vkms_crtc_init(vkmsdev, primary, cursor, item->ci_name);
> > +		if (IS_ERR(vkms_crtc)) {
> > +			DRM_WARN("Unable to init crtc from config: %s",
> > +				 item->ci_name);
> > +			return PTR_ERR(vkms_crtc);
> > +		}
> > +
> > +		for (int j = 0; j < output->num_planes; j++) {
> > +			struct plane_map *plane_entry = &plane_map[j];
> > +
> > +			if (!plane_entry->plane)
> > +				break;
> > +
> > +			if (is_object_linked(
> > +				    &plane_entry->config_plane->possible_crtcs,
> > +				    config_crtc->crtc_config_idx)) {
> > +				plane_entry->plane->base.possible_crtcs |=
> > +					drm_crtc_mask(&vkms_crtc->base);
> > +			}
> > +		}
> > +
> > +		for (int j = 0; j < output->num_encoders; j++) {
> > +			struct encoder_map *encoder_entry = &encoder_map[j];
> > +
> > +			if (is_object_linked(&encoder_entry->config_encoder
> > +						      ->possible_crtcs,
> > +					     config_crtc->crtc_config_idx)) {
> > +				encoder_entry->encoder->possible_crtcs |=
> > +					drm_crtc_mask(&vkms_crtc->base);
> > +			}
> > +		}
> > +
> > +		if (vkmsdev->config.writeback) {
> > +			int ret = vkms_enable_writeback_connector(vkmsdev,
> > +								  vkms_crtc);
> > +			if (ret)
> > +				DRM_WARN(
> > +					"Failed to init writeback connector for config crtc: %s. Error code %d",
> > +					item->ci_name, ret);
> > +		}
> > +	}
> I think we might be needing here a test for missing symlinks - invalid
> configurations, like unused crtcs, encoders, connectors. I
> suppose anything that's not matched with is_object_linked(),
> such we avoid invalid configuration found by drm_mode_config_validate()
> and inform users about missing them.
>
> An example here would be to create a second encoder, connector, crtc and
> not symlink them to their possible_encoders,possible_crtcs mask. An
> i-g-t test for this very thing would be needed to stress different kind
> of combinations.

I wonder about this.  Shouldn't a user be free to create dangling files 
to simulate some scenario?

I could see a further development to publish a warning in the log, but 
disallowing it seems overly restrictive.

Either way we could accomplish this pretty easily by adding a flag to 
each vkms object in the form of `bool is_linked` and set it when we 
detect it's linked.  Then at the end iterate through all planes, 
encoders, connectors, crtcs that can be linked and if they are not just 
publish a warning saying

kwarn: "crtc/plane/encoder $NAME is created but unlinked"

IGT tests to test that that was done make sense to me.

> > +
> > +	drm_mode_config_reset(dev);
> > +
> > +	return 0;
> >   }
> > --
> > 2.41.0.162.gfafddb0af9-goog