Re: [PATCH 5/5] drm/vkms: Support registering configfs devices

Sean Paul
2022-08-08T15:17:33Z

On Fri, Jul 22, 2022 at 05:32:13PM -0400, Jim Shargo wrote:
> VKMS now supports creating virtual cards and registering them to create
> real drm devices.
>
> In addition to the registration logic, this commit also prevents users
> from adding new objects once a card is registered.
>
> Signed-off-by: Jim Shargo <jshargo@chromium.org>
> ---
> drivers/gpu/drm/vkms/vkms_configfs.c | 27 +++-
> drivers/gpu/drm/vkms/vkms_drv.c | 21 ++-
> drivers/gpu/drm/vkms/vkms_drv.h | 3 +
> drivers/gpu/drm/vkms/vkms_output.c | 227 ++++++++++++++++++++++++---
> 4 files changed, 251 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/gpu/drm/vkms/vkms_configfs.c b/drivers/gpu/drm/vkms/vkms_configfs.c
> index fa0d8700258e..6f0f4e39864a 100644
> --- a/drivers/gpu/drm/vkms/vkms_configfs.c
> +++ b/drivers/gpu/drm/vkms/vkms_configfs.c
> @@ -326,8 +326,15 @@ static struct config_item_type plane_type = {
> static struct config_group *connectors_group_make(struct config_group *group,
> const char *name)
> {
> - struct vkms_config_connector *connector =
> - kzalloc(sizeof(struct vkms_config_connector), GFP_KERNEL);
> + struct vkms_configfs *configfs =
> + container_of(group, struct vkms_configfs, connectors_group);
> + struct vkms_config_connector *connector;
> +
> + if (configfs->card) {

I think it would be better to assign configfs->card in
card_is_registered_store() after successful call to vkms_card_init(). My
reasoning is that the functions in this file care about configfs->card, and not
vkms_drv.c. As a bonus, you can also eliminate the if (configfs) check before
the assignment which is necessary in vkms_card_init() but not
card_is_registered_store().

> + return ERR_PTR(EBUSY);

Nit: Negative errno please (applies elsewhere through the patch as well).

> + }

Nit: remove braces

> +
> + connector = kzalloc(sizeof(struct vkms_config_connector), GFP_KERNEL);

Nit: sizeof(*connector) could be handy here and elsewhere below.

It's a bit awkward to make use of devres elsewhere and not here. I guess the
devres group doesn't exist at this point and perhaps card destruction and
config_group destruction aren't strictly ordered. ¯\_(ツ)_/¯

> if (!connector)
> return ERR_PTR(ENOMEM);
>
> @@ -368,6 +375,9 @@ static struct config_group *crtcs_group_make(struct config_group *group,
> VKMS_MAX_OUTPUT_OBJECTS);
> struct vkms_config_crtc *crtc;
>
> + if (configfs->card)

It really feels like we should have some locking protecting us from races
between adding new components and registration.

> + return ERR_PTR(EBUSY);
> +
> if (next_idx == VKMS_MAX_OUTPUT_OBJECTS) {
> DRM_ERROR("Unable to allocate another CRTC.");
> return ERR_PTR(ENOMEM);
> @@ -413,6 +423,9 @@ static struct config_group *encoders_group_make(struct config_group *group,
> &configfs->allocated_encoders, VKMS_MAX_OUTPUT_OBJECTS);
> struct vkms_config_encoder *encoder;
>
> + if (configfs->card)
> + return ERR_PTR(EBUSY);
> +
> if (next_idx == VKMS_MAX_OUTPUT_OBJECTS) {
> DRM_ERROR("Unable to allocate another encoder.");
> return ERR_PTR(ENOMEM);
> @@ -454,8 +467,14 @@ static struct config_item_type encoders_group_type = {
> static struct config_group *make_plane_group(struct config_group *group,
> const char *name)
> {
> - struct vkms_config_plane *plane =
> - kzalloc(sizeof(struct vkms_config_plane), GFP_KERNEL);
> + struct vkms_configfs *configfs =
> + container_of(group, struct vkms_configfs, planes_group);
> + struct vkms_config_plane *plane;
> +
> + if (configfs->card)
> + return ERR_PTR(EBUSY);
> +
> + plane = kzalloc(sizeof(struct vkms_config_plane), GFP_KERNEL);
> if (!plane)
> return ERR_PTR(ENOMEM);
>
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
> index 37b95ca28672..4e00f3b0de7d 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.c
> +++ b/drivers/gpu/drm/vkms/vkms_drv.c
> @@ -216,7 +216,7 @@ struct vkms_card *vkms_card_init(const char *name, struct vkms_configfs *configf
> goto out_release_group;
> }
>
> - ret = drm_vblank_init(&card->drm, 1);
> + ret = drm_vblank_init(&card->drm, vkms_card_crtc_count(card));

I wonder if you could re-order this below vkms_modeset_init() and use
card->output.num_crtcs instead of the new function?

> if (ret) {
> DRM_ERROR("Failed to vblank\n");
> goto out_release_group;
> @@ -231,7 +231,7 @@ struct vkms_card *vkms_card_init(const char *name, struct vkms_configfs *configf
> ret = drm_dev_register(&card->drm, 0);
> if (ret) {
> DRM_ERROR("Unable to register card");
> - return ERR_PTR(ret);
> + goto out_modeset;

Not sure if this is the one I commented on in the previous patch, but at the
risk of duplicate comments, this cleanup feels like it belongs in an earlier patch.

> }
>
> drm_fbdev_generic_setup(&card->drm, 0);
> @@ -245,6 +245,8 @@ struct vkms_card *vkms_card_init(const char *name, struct vkms_configfs *configf
>
> return card;
>
> +out_modeset:
> + vkms_output_clear(card);
> out_release_group:
> devres_release_group(&pdev->dev, grp);
> out_platform_device:
> @@ -264,6 +266,21 @@ void vkms_card_destroy(struct vkms_card *card)

I feel like vkms_card_destroy() should also be calling vkms_output_clear() or it
should have the same cleanup procedure as the error handling code in
vkms_card_init().

> }
> }
>
> +int vkms_card_crtc_count(struct vkms_card *card)

AFAICT this isn't used outside vkms_drv.c so it should be static.

> +{
> + struct list_head *item;
> + int count = 0;
> +
> + if (card->is_default)
> + return 1;
> +
> + BUG_ON(!card->configfs);
> + list_for_each(item, &card->configfs->crtcs_group.cg_children) {

Do you need any locking here?

> + count += 1;
> + }
> + return count;
> +}
> +
> static int __init vkms_init(void)
> {
> struct vkms_card *card;
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> index f43e4c563863..2e6bfed890f9 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.h
> +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> @@ -222,11 +222,14 @@ struct vkms_card *vkms_card_init(const char *name,
> struct vkms_configfs *configfs);
> void vkms_card_destroy(struct vkms_card *card);
>
> +int vkms_card_crtc_count(struct vkms_card *card);
> +
> /* CRTC */
> struct vkms_crtc *vkms_crtc_init(struct vkms_card *card, struct drm_plane *primary, struct drm_plane *cursor);
>
> int vkms_output_init_default(struct vkms_card *card, int index);
> int vkms_output_init(struct vkms_card *card, int index);
> +void vkms_output_clear(struct vkms_card *card);
>
> struct vkms_plane *vkms_plane_init(struct vkms_card *card,
> enum drm_plane_type type);
> diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c
> index e343a9c1f311..857cd8593dce 100644
> --- a/drivers/gpu/drm/vkms/vkms_output.c
> +++ b/drivers/gpu/drm/vkms/vkms_output.c
> @@ -4,6 +4,10 @@
> #include <linux/kernel.h>
>
> #include <drm/drm_atomic_helper.h>
> +#include <drm/drm_connector.h>
> +#include <drm/drm_crtc.h>
> +#include <drm/drm_encoder.h>
> +#include <drm/drm_plane.h>

It makes sense that we would need these, but I'm not sure why it's now and not
earlier in the patchset.

> #include <drm/drm_probe_helper.h>
> #include <drm/drm_simple_kms_helper.h>
>
> @@ -46,7 +50,7 @@ static struct drm_connector *vkms_connector_init(struct vkms_card *card)
>
> connector = &card->output.connectors[card->output.num_connectors++];
> ret = drm_connector_init(&card->drm, connector, &vkms_connector_funcs,
> - DRM_MODE_CONNECTOR_VIRTUAL);
> + DRM_MODE_CONNECTOR_VIRTUAL);

Nit: This indent was introduced in patch 3, if you fix it there it'll drop out of here.

> if (ret) {
> memset(connector, 0, sizeof(*connector));
> card->output.num_connectors -= 1;
> @@ -79,7 +83,6 @@ static struct drm_encoder *vkms_encoder_init(struct vkms_card *card)
> int vkms_output_init_default(struct vkms_card *card, int index)

How feasible would it be to initialize the default device in configfs with the
module config and then call vkms_output_init() to initialize it instead of
duplicating all of this init? As a bonus, we could probably turf some of the
if(default) logic sprinkled around.

> {
> const struct vkms_config *config = &card->vkms_device->config;
> - struct vkms_output *output = &card->output;
> struct drm_device *dev = &card->drm;
> struct drm_connector *connector;
> struct drm_encoder *encoder;
> @@ -99,7 +102,7 @@ int vkms_output_init_default(struct vkms_card *card, int index)
> vkms_plane_init(card, DRM_PLANE_TYPE_OVERLAY);
> if (IS_ERR(overlay)) {
> ret = PTR_ERR(overlay);
> - goto err_planes;
> + goto cleanup_output;
> }
> }
> }
> @@ -108,7 +111,7 @@ int vkms_output_init_default(struct vkms_card *card, int index)
> cursor = vkms_plane_init(card, DRM_PLANE_TYPE_CURSOR);
> if (IS_ERR(cursor)) {
> ret = PTR_ERR(cursor);
> - goto err_planes;
> + goto cleanup_output;
> }
> }
>
> @@ -117,7 +120,7 @@ int vkms_output_init_default(struct vkms_card *card, int index)
> if (IS_ERR(vkms_crtc)) {
> DRM_ERROR("Failed to init crtc\n");
> ret = PTR_ERR(vkms_crtc);
> - goto err_planes;
> + goto cleanup_output;
> }
>
> for (int i = 0; i < card->output.num_planes; i++) {
> @@ -129,22 +132,21 @@ int vkms_output_init_default(struct vkms_card *card, int index)
> if (IS_ERR(connector)) {
> DRM_ERROR("Failed to init connector\n");
> ret = PTR_ERR(connector);
> - goto err_connector;
> + goto cleanup_output;
> }
>
> encoder = vkms_encoder_init(card);
> if (IS_ERR(encoder)) {
> DRM_ERROR("Failed to init encoder\n");
> ret = PTR_ERR(encoder);
> - goto err_encoder;
> + goto cleanup_output;
> }
> encoder->possible_crtcs |= drm_crtc_mask(&vkms_crtc->base);
>
> -

Nit: This blank line was introduced in patch 3, perhaps remove it from there and
it'll drop out here.

> ret = drm_connector_attach_encoder(connector, encoder);
> if (ret) {
> DRM_ERROR("Failed to attach connector to encoder\n");
> - goto err_attach;
> + goto cleanup_output;
> }
>
> if (config->writeback) {
> @@ -157,26 +159,209 @@ int vkms_output_init_default(struct vkms_card *card, int index)
>
> return 0;
>
> -err_attach:
> - drm_encoder_cleanup(encoder);
> +cleanup_output:
> + vkms_output_clear(card);
> + return ret;
> +}
>
> -err_encoder:
> - drm_connector_cleanup(connector);
> +static bool is_object_linked(struct vkms_config_links *links, unsigned long idx)
> +{
> + return links->linked_object_bitmap & (1 << idx);

Nit: You could use some of the bit helpers available (and avoid the implicit
cast):

return FIELD_GET(BIT(idx), links->linked_object_bitmap) != 0;

> +}
>
> -err_connector:
> - drm_crtc_cleanup(&vkms_crtc->base);
> +int vkms_output_init(struct vkms_card *card, int index)
> +{
> + struct drm_device *dev = &card->drm;
> + struct vkms_configfs *configfs = card->configfs;
> + struct vkms_output *output = &card->output;
> + struct plane_map {
> + struct vkms_config_plane *config_plane;
> + struct vkms_plane *plane;
> + } plane_map[VKMS_MAX_OUTPUT_OBJECTS] = { 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 i, ret;
> +
> + i = 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(card, config_plane->type);
> +
> + if (IS_ERR(plane)) {
> + DRM_ERROR("Unable to init plane from config: %s",
> + item->ci_name);

It'd be nice to print the return value here.

> + ret = PTR_ERR(plane);
> + goto cleanup_output;
> + }
>
> -err_planes:
> - for (int i = 0; i < output->num_planes; i++) {
> - drm_plane_cleanup(&output->planes[i].base);
> + plane_map[i].config_plane = config_plane;
> + plane_map[i].plane = plane;
> + i += 1;

Instead of tracking with i, you could use "output->num_planes - 1"? Same comment
below for different "num_blah"

> + }
> +
> + i = 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(card);
> +
> + if (IS_ERR(encoder)) {
> + DRM_ERROR("Failed to init config encoder: %s",
> + item->ci_name);
> + ret = PTR_ERR(encoder);
> + goto cleanup_output;
> + }
> + encoder_map[i].config_encoder = config_encoder;
> + encoder_map[i].encoder = encoder;
> + i += 1;
> + }
> +
> + 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(card);
> +
> + if (IS_ERR(connector)) {
> + DRM_ERROR("Failed to init connector from config: %s",
> + item->ci_name);
> + ret = PTR_ERR(connector);
> + goto cleanup_output;
> + }
> +
> + 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)) {
> + 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;
> + }

Nit: Braces

> +
> + if (plane->type == DRM_PLANE_TYPE_PRIMARY) {
> + if (primary) {
> + DRM_WARN(
> + "Too many primary planes found for crtc %s.",
> + item->ci_name);

Nit: drm_dbg()

> + ret = EINVAL;
> + goto cleanup_output;
> + }
> + 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);
> + ret = EINVAL;
> + goto cleanup_output;
> + }
> + cursor = plane;
> + }
> + }
> +
> + if (!primary) {
> + DRM_WARN("No primary plane configured for crtc %s", item->ci_name);
> + ret = EINVAL;
> + goto cleanup_output;
> + }
> +
> + // TODO add names to helper

Mind expanding on this?

> + vkms_crtc = vkms_crtc_init(card, primary, cursor);
> + if (IS_ERR(vkms_crtc)) {
> + DRM_WARN("Unable to init crtc from config: %s",
> + item->ci_name);
> + ret = PTR_ERR(vkms_crtc);
> + goto cleanup_output;
> + }
> +
> + 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 (card->vkms_device->config.writeback) {
> + ret = vkms_enable_writeback_connector(card, vkms_crtc);
> + if (ret)
> + DRM_WARN(
> + "Failed to init writeback connector for config crtc: %s",
> + item->ci_name);

Nit: drm_dbg and please print the error message.

> + }
> }
>
> - memset(output, 0, sizeof(struct vkms_output));
> + drm_mode_config_reset(dev);
> +
> + return 0;
>
> +cleanup_output:
> + vkms_output_clear(card);
> + resume_device_irqs(); // REMOVE

REMOVE?

> return ret;
> }
>
> -int vkms_output_init(struct vkms_card *card, int index)
> +void vkms_output_clear(struct vkms_card *card)
> {
> - return -ENOTSUPP;
> + struct vkms_output *output = &card->output;
> +
> + for (int i = 0; i < output->num_crtcs; i++) {
> + drm_crtc_cleanup(&output->crtcs[i].base);
> + }
> + for (int i = 0; i < output->num_encoders; i++) {
> + drm_encoder_cleanup(&output->encoders[i]);
> + }
> + for (int i = 0; i < output->num_connectors; i++) {
> + drm_connector_cleanup(&output->connectors[i]);
> + }
> + for (int i = 0; i < output->num_planes; i++) {
> + drm_plane_cleanup(&output->planes[i].base);
> + }

Nit: braces for all of these

> +
> + memset(output, 0, sizeof(*output));

Same concerns about memset as before.