On 18/02/25 - 18:07, José Expósito wrote:
> Allow to create, enable, disable and destroy VKMS instances using
> configfs.
>
> For the moment, it is not possible to add pipeline items, so trying to
> enable the device will fail printing an informative error to the log.
>
> Co-developed-by: Louis Chauvet <louis.chauvet@xxxxxxxxxxx>
> Signed-off-by: Louis Chauvet <louis.chauvet@xxxxxxxxxxx>
> Signed-off-by: José Expósito <jose.exposito89@xxxxxxxxx>
Reviewed-by: Louis Chauvet <louis.chauvet@xxxxxxxxxxx>
> ---
> Documentation/gpu/vkms.rst | 32 +++++
> drivers/gpu/drm/vkms/Kconfig | 1 +
> drivers/gpu/drm/vkms/Makefile | 3 +-
> drivers/gpu/drm/vkms/vkms_configfs.c | 181 +++++++++++++++++++++++++++
> drivers/gpu/drm/vkms/vkms_configfs.h | 8 ++
> drivers/gpu/drm/vkms/vkms_drv.c | 7 ++
> 6 files changed, 231 insertions(+), 1 deletion(-)
> create mode 100644 drivers/gpu/drm/vkms/vkms_configfs.c
> create mode 100644 drivers/gpu/drm/vkms/vkms_configfs.h
>
> diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
> index ba04ac7c2167..423bdf86b5b1 100644
> --- a/Documentation/gpu/vkms.rst
> +++ b/Documentation/gpu/vkms.rst
> @@ -51,6 +51,38 @@ To disable the driver, use ::
>
> sudo modprobe -r vkms
>
> +Configuring With Configfs
> +=========================
> +
> +It is possible to create and configure multiple VKMS instances via configfs.
> +
> +Start by mounting configfs and loading VKMS::
> +
> + sudo mount -t configfs none /config
> + sudo modprobe vkms
> +
> +Once VKMS is loaded, ``/config/vkms`` is created automatically. Each directory
> +under ``/config/vkms`` represents a VKMS instance, create a new one::
> +
> + sudo mkdir /config/vkms/my-vkms
> +
> +By default, the instance is disabled::
> +
> + cat /config/vkms/my-vkms/enabled
> + 0
> +
> +Once you are done configuring the VKMS instance, enable it::
> +
> + echo "1" | sudo tee /config/vkms/my-vkms/enabled
> +
> +Finally, you can remove the VKMS instance disabling it::
> +
> + echo "0" | sudo tee /config/vkms/my-vkms/enabled
> +
> +And removing the top level directory::
> +
> + sudo rmdir /config/vkms/my-vkms
> +
> Testing With IGT
> ================
>
> diff --git a/drivers/gpu/drm/vkms/Kconfig b/drivers/gpu/drm/vkms/Kconfig
> index 3c02f928ffe6..3977bbb99f7d 100644
> --- a/drivers/gpu/drm/vkms/Kconfig
> +++ b/drivers/gpu/drm/vkms/Kconfig
> @@ -7,6 +7,7 @@ config DRM_VKMS
> select DRM_KMS_HELPER
> select DRM_GEM_SHMEM_HELPER
> select CRC32
> + select CONFIGFS_FS
> default n
> help
> Virtual Kernel Mode-Setting (VKMS) is used for testing or for
> diff --git a/drivers/gpu/drm/vkms/Makefile b/drivers/gpu/drm/vkms/Makefile
> index d657865e573f..939991fc8233 100644
> --- a/drivers/gpu/drm/vkms/Makefile
> +++ b/drivers/gpu/drm/vkms/Makefile
> @@ -8,7 +8,8 @@ vkms-y := \
> vkms_composer.o \
> vkms_writeback.o \
> vkms_connector.o \
> - vkms_config.o
> + vkms_config.o \
> + vkms_configfs.o
>
> obj-$(CONFIG_DRM_VKMS) += vkms.o
> obj-$(CONFIG_DRM_VKMS_KUNIT_TEST) += tests/
> diff --git a/drivers/gpu/drm/vkms/vkms_configfs.c b/drivers/gpu/drm/vkms/vkms_configfs.c
> new file mode 100644
> index 000000000000..306f571559b7
> --- /dev/null
> +++ b/drivers/gpu/drm/vkms/vkms_configfs.c
> @@ -0,0 +1,181 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +#include <linux/configfs.h>
> +#include <linux/mutex.h>
> +#include <linux/slab.h>
> +
> +#include "vkms_drv.h"
> +#include "vkms_config.h"
> +#include "vkms_configfs.h"
> +
> +/* To avoid registering configfs more than once or unregistering on error */
> +static bool is_configfs_registered;
> +
> +/**
> + * struct vkms_configfs_device - Configfs representation of a VKMS device
> + *
> + * @group: Top level configuration group that represents a VKMS device.
> + * Initialized when a new directory is created under "/config/vkms/"
> + * @lock: Lock used to project concurrent access to the configuration attributes
> + * @config: Protected by @lock. Configuration of the VKMS device
> + * @enabled: Protected by @lock. The device is created or destroyed when this
> + * option changes
> + */
> +struct vkms_configfs_device {
> + struct config_group group;
> +
> + struct mutex lock;
> + struct vkms_config *config;
> + bool enabled;
> +};
> +
> +#define device_item_to_vkms_configfs_device(item) \
> + container_of(to_config_group((item)), struct vkms_configfs_device, \
> + group)
> +
> +static ssize_t device_enabled_show(struct config_item *item, char *page)
> +{
> + struct vkms_configfs_device *dev;
> + bool enabled;
> +
> + dev = device_item_to_vkms_configfs_device(item);
> +
> + mutex_lock(&dev->lock);
> + enabled = dev->enabled;
> + mutex_unlock(&dev->lock);
> +
> + return sprintf(page, "%d\n", enabled);
> +}
> +
> +static ssize_t device_enabled_store(struct config_item *item, const char *page,
> + size_t count)
> +{
> + struct vkms_configfs_device *dev;
> + bool enabled;
> + int ret = 0;
> +
> + dev = device_item_to_vkms_configfs_device(item);
> +
> + if (kstrtobool(page, &enabled))
> + return -EINVAL;
> +
> + mutex_lock(&dev->lock);
> +
> + if (!dev->enabled && enabled) {
> + if (!vkms_config_is_valid(dev->config)) {
> + ret = -EINVAL;
> + goto err_unlock;
> + }
> +
> + ret = vkms_create(dev->config);
> + } else if (dev->enabled && !enabled) {
> + vkms_destroy(dev->config);
> + }
> +
> + if (ret)
> + goto err_unlock;
> +
> + dev->enabled = enabled;
> +
> + mutex_unlock(&dev->lock);
> +
> + return (ssize_t)count;
> +
> +err_unlock:
> + mutex_unlock(&dev->lock);
> + return ret;
> +}
> +
> +CONFIGFS_ATTR(device_, enabled);
> +
> +static struct configfs_attribute *device_item_attrs[] = {
> + &device_attr_enabled,
> + NULL,
> +};
> +
> +static void device_release(struct config_item *item)
> +{
> + struct vkms_configfs_device *dev;
> +
> + dev = device_item_to_vkms_configfs_device(item);
> +
> + if (dev->enabled)
> + vkms_destroy(dev->config);
> +
> + mutex_destroy(&dev->lock);
> + vkms_config_destroy(dev->config);
> + kfree(dev);
> +}
> +
> +static struct configfs_item_operations device_item_operations = {
> + .release = &device_release,
> +};
> +
> +static const struct config_item_type device_item_type = {
> + .ct_attrs = device_item_attrs,
> + .ct_item_ops = &device_item_operations,
> + .ct_owner = THIS_MODULE,
> +};
> +
> +static struct config_group *make_device_group(struct config_group *group,
> + const char *name)
> +{
> + struct vkms_configfs_device *dev;
> +
> + if (strcmp(name, DEFAULT_DEVICE_NAME) == 0)
> + return ERR_PTR(-EINVAL);
> +
> + dev = kzalloc(sizeof(*dev), GFP_KERNEL);
> + if (!dev)
> + return ERR_PTR(-ENOMEM);
> +
> + dev->config = vkms_config_create(name);
> + if (IS_ERR(dev->config)) {
> + kfree(dev);
> + return ERR_CAST(dev->config);
> + }
> +
> + config_group_init_type_name(&dev->group, name, &device_item_type);
> + mutex_init(&dev->lock);
> +
> + return &dev->group;
> +}
> +
> +static struct configfs_group_operations device_group_ops = {
> + .make_group = &make_device_group,
> +};
> +
> +static const struct config_item_type device_group_type = {
> + .ct_group_ops = &device_group_ops,
> + .ct_owner = THIS_MODULE,
> +};
> +
> +static struct configfs_subsystem vkms_subsys = {
> + .su_group = {
> + .cg_item = {
> + .ci_name = "vkms",
> + .ci_type = &device_group_type,
> + },
> + },
> + .su_mutex = __MUTEX_INITIALIZER(vkms_subsys.su_mutex),
> +};
> +
> +int vkms_configfs_register(void)
> +{
> + int ret;
> +
> + if (is_configfs_registered)
> + return 0;
> +
> + config_group_init(&vkms_subsys.su_group);
> + ret = configfs_register_subsystem(&vkms_subsys);
> +
> + is_configfs_registered = ret == 0;
> +
> + return ret;
> +}
> +
> +void vkms_configfs_unregister(void)
> +{
> + if (is_configfs_registered)
> + configfs_unregister_subsystem(&vkms_subsys);
> +}
> diff --git a/drivers/gpu/drm/vkms/vkms_configfs.h b/drivers/gpu/drm/vkms/vkms_configfs.h
> new file mode 100644
> index 000000000000..e9020b0043db
> --- /dev/null
> +++ b/drivers/gpu/drm/vkms/vkms_configfs.h
> @@ -0,0 +1,8 @@
> +/* SPDX-License-Identifier: GPL-2.0+ */
> +#ifndef _VKMS_CONFIGFS_H_
> +#define _VKMS_CONFIGFS_H_
> +
> +int vkms_configfs_register(void);
> +void vkms_configfs_unregister(void);
> +
> +#endif /* _VKMS_CONFIGFS_H_ */
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
> index 23817c7b997e..5bcfbcb6c0c5 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.c
> +++ b/drivers/gpu/drm/vkms/vkms_drv.c
> @@ -28,6 +28,7 @@
> #include <drm/drm_vblank.h>
>
> #include "vkms_config.h"
> +#include "vkms_configfs.h"
> #include "vkms_drv.h"
>
> #define DRIVER_NAME "vkms"
> @@ -214,6 +215,10 @@ static int __init vkms_init(void)
> int ret;
> struct vkms_config *config;
>
> + ret = vkms_configfs_register();
> + if (ret)
> + return ret;
> +
> config = vkms_config_default_create(enable_cursor, enable_writeback, enable_overlay);
> if (IS_ERR(config))
> return PTR_ERR(config);
> @@ -250,6 +255,8 @@ void vkms_destroy(struct vkms_config *config)
>
> static void __exit vkms_exit(void)
> {
> + vkms_configfs_unregister();
> +
> if (!default_config)
> return;
>
> --
> 2.48.1
>
