[PATCH v4 2/4] drm: add debugfs support on per client-id basis

[Christian König]

On 6/18/25 15:47, Sunil Khatri wrote:
> add support to add a directory for each client-id
> with root at the dri level. Since the clients are
> unique and not just related to one single drm device,
> so it makes more sense to add all the client based
> nodes with root as dri.
> 
> Also create a symlink back to the parent drm device
> from each client.
> 
> Signed-off-by: Sunil Khatri <sunil.khatri at amd.com>
> ---
>  drivers/gpu/drm/drm_debugfs.c | 32 ++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/drm_file.c    | 10 ++++++++++
>  include/drm/drm_debugfs.h     | 12 ++++++++++++
>  include/drm/drm_file.h        |  7 +++++++
>  4 files changed, 61 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
> index 5a33ec299c04..875276d5fb9f 100644
> --- a/drivers/gpu/drm/drm_debugfs.c
> +++ b/drivers/gpu/drm/drm_debugfs.c
> @@ -298,6 +298,38 @@ void drm_debugfs_remove_dir(void)
>  	debugfs_remove(drm_debugfs_root);
>  }
>  
> +int drm_debugfs_clients_add(struct drm_file *file)
> +{
> +	struct drm_device *dev;
> +	char *client_dir, *symlink;
> +
> +	dev = file->minor->dev;
> +
> +	client_dir = kasprintf(GFP_KERNEL, "client-%llu", file->client_id);
> +	if (!client_dir)
> +		return -ENOMEM;
> +
> +	/* Create a debugfs directory for the client in root on drm debugfs */

That comments on what is done, so probably not a good idea.

But we should certainly have some explanation why we do this! Probably best to add some overview under Documentation/gpu.

Apart from that this works technically for me.

Regards,
Christian.


> +	file->debugfs_client = debugfs_create_dir(client_dir, drm_debugfs_root);
> +	kfree(client_dir);
> +
> +	symlink = kasprintf(GFP_KERNEL, "../%s", dev->unique);
> +	if (!symlink)
> +		return -ENOMEM;
> +
> +	/* Create a link from client_id to the drm device this client id belongs to */
> +	debugfs_create_symlink("device", file->debugfs_client, symlink);
> +	kfree(symlink);
> +
> +	return 0;
> +}
> +
> +void drm_debugfs_clients_remove(struct drm_file *file)
> +{
> +	debugfs_remove_recursive(file->debugfs_client);
> +	file->debugfs_client = NULL;
> +}
> +
>  /**
>   * drm_debugfs_dev_init - create debugfs directory for the device
>   * @dev: the device which we want to create the directory for
> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
> index 06ba6dcbf5ae..8502c5a630b1 100644
> --- a/drivers/gpu/drm/drm_file.c
> +++ b/drivers/gpu/drm/drm_file.c
> @@ -39,12 +39,14 @@
>  #include <linux/poll.h>
>  #include <linux/slab.h>
>  #include <linux/vga_switcheroo.h>
> +#include <linux/debugfs.h>
>  
>  #include <drm/drm_client_event.h>
>  #include <drm/drm_drv.h>
>  #include <drm/drm_file.h>
>  #include <drm/drm_gem.h>
>  #include <drm/drm_print.h>
> +#include <drm/drm_debugfs.h>
>  
>  #include "drm_crtc_internal.h"
>  #include "drm_internal.h"
> @@ -143,6 +145,13 @@ struct drm_file *drm_file_alloc(struct drm_minor *minor)
>  	rcu_assign_pointer(file->pid, get_pid(task_tgid(current)));
>  	file->minor = minor;
>  
> +	ret = drm_debugfs_clients_add(file);
> +	if (ret) {
> +		put_pid(rcu_access_pointer(file->pid));
> +		kfree(file);
> +		return ERR_PTR(ret);
> +	}
> +
>  	/* for compatibility root is always authenticated */
>  	file->authenticated = capable(CAP_SYS_ADMIN);
>  
> @@ -236,6 +245,7 @@ void drm_file_free(struct drm_file *file)
>  		     atomic_read(&dev->open_count));
>  
>  	drm_events_release(file);
> +	drm_debugfs_clients_remove(file);
>  
>  	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
>  		drm_fb_release(file);
> diff --git a/include/drm/drm_debugfs.h b/include/drm/drm_debugfs.h
> index cf06cee4343f..4bd6cc1d0900 100644
> --- a/include/drm/drm_debugfs.h
> +++ b/include/drm/drm_debugfs.h
> @@ -153,6 +153,9 @@ void drm_debugfs_add_files(struct drm_device *dev,
>  
>  int drm_debugfs_gpuva_info(struct seq_file *m,
>  			   struct drm_gpuvm *gpuvm);
> +
> +int drm_debugfs_clients_add(struct drm_file *file);
> +void drm_debugfs_clients_remove(struct drm_file *file);
>  #else
>  static inline void drm_debugfs_create_files(const struct drm_info_list *files,
>  					    int count, struct dentry *root,
> @@ -181,6 +184,15 @@ static inline int drm_debugfs_gpuva_info(struct seq_file *m,
>  {
>  	return 0;
>  }
> +
> +int drm_debugfs_clients_add(struct drm_file *file)
> +{
> +	return 0;
> +}
> +
> +void drm_debugfs_clients_remove(struct drm_file *file)
> +{
> +}
>  #endif
>  
>  #endif /* _DRM_DEBUGFS_H_ */
> diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
> index 5c3b2aa3e69d..eab7546aad79 100644
> --- a/include/drm/drm_file.h
> +++ b/include/drm/drm_file.h
> @@ -400,6 +400,13 @@ struct drm_file {
>  	 * @client_name_lock: Protects @client_name.
>  	 */
>  	struct mutex client_name_lock;
> +
> +	/**
> +	 * @debugfs_client:
> +	 *
> +	 * debugfs directory for each client under a drm node.
> +	 */
> +	struct dentry *debugfs_client;
>  };
>  
>  /**