[PATCH v2 2/2] drm: add debugfs support on per client-id basis

[Khatri, Sunil]

On 6/16/2025 5:41 PM, Christian König wrote:
> On 6/16/25 12:05, 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 |  1 +
>>   drivers/gpu/drm/drm_file.c    | 26 ++++++++++++++++++++++++++
>>   include/drm/drm_device.h      |  4 ++++
>>   include/drm/drm_file.h        |  7 +++++++
>>   4 files changed, 38 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
>> index 2d43bda82887..b4956960ae76 100644
>> --- a/drivers/gpu/drm/drm_debugfs.c
>> +++ b/drivers/gpu/drm/drm_debugfs.c
>> @@ -296,6 +296,7 @@ EXPORT_SYMBOL(drm_debugfs_remove_files);
>>   void drm_debugfs_dev_init(struct drm_device *dev, struct dentry *root)
>>   {
>>   	dev->debugfs_root = debugfs_create_dir(dev->unique, root);
>> +	dev->drm_debugfs_root = root;
> We should probably just move drm_debugfs_root into drm_debugfs.c instead of keeping that around per device.
root node above is needed in the drm_file.c function drm_alloc and there 
is nothing above drm_device where i can get the root information. that 
is the reason i mentioned it as drm_debugfs_root as root node of the drm 
subsystem itself.
~Sunil
>
>>   }
>>   
>>   /**
>> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
>> index 06ba6dcbf5ae..32012e39dcb4 100644
>> --- a/drivers/gpu/drm/drm_file.c
>> +++ b/drivers/gpu/drm/drm_file.c
>> @@ -39,6 +39,7 @@
>>   #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>
>> @@ -133,6 +134,7 @@ struct drm_file *drm_file_alloc(struct drm_minor *minor)
>>   	struct drm_device *dev = minor->dev;
>>   	struct drm_file *file;
>>   	int ret;
>> +	char *dir_name, *drm_name, *symlink;
>>   
>>   	file = kzalloc(sizeof(*file), GFP_KERNEL);
>>   	if (!file)
>> @@ -143,6 +145,27 @@ struct drm_file *drm_file_alloc(struct drm_minor *minor)
>>   	rcu_assign_pointer(file->pid, get_pid(task_tgid(current)));
>>   	file->minor = minor;
>>   
>> +	dir_name = kasprintf(GFP_KERNEL, "client-%llu", file->client_id);
>> +	if (!dir_name)
>> +		return ERR_PTR(-ENOMEM);
>> +
>> +	/* Create a debugfs directory for the client in root on drm debugfs */
>> +	file->debugfs_client = debugfs_create_dir(dir_name, dev->drm_debugfs_root);
>> +	kfree(dir_name);
>> +
>> +	drm_name = kasprintf(GFP_KERNEL, "%d", minor->index);
>> +	if (!drm_name)
>> +		return ERR_PTR(-ENOMEM);
>> +
>> +	symlink = kasprintf(GFP_KERNEL, "../%d", minor->index);
> Better use dev->unique here, minor->index is also only a symlink.

Thats a good suggestion and doable. Will update in next version

~Sunil

>
>> +	if (!symlink)
>> +		return ERR_PTR(-ENOMEM);
>> +
>> +	/* Create a link from client_id to the drm device this client id belongs to */
>> +	debugfs_create_symlink(drm_name, file->debugfs_client, symlink);
>> +	kfree(drm_name);
>> +	kfree(symlink);
>> +
> Move all that debugfs handling into a function in drm_debugfs.c
Sure, let me try that and push another patch.
>
>>   	/* for compatibility root is always authenticated */
>>   	file->authenticated = capable(CAP_SYS_ADMIN);
>>   
>> @@ -237,6 +260,9 @@ void drm_file_free(struct drm_file *file)
>>   
>>   	drm_events_release(file);
>>   
>> +	debugfs_remove_recursive(file->debugfs_client);
>> +	file->debugfs_client = NULL;
>> +
> Same here, move to drm_debugfs.c

Sure, let me try that if there are not challenges.

~sunil

>
> Apart from that looks solid to me.
>
> Regards,
> Christian.
>
>
>>   	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
>>   		drm_fb_release(file);
>>   		drm_property_destroy_user_blobs(dev, file);
>> diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
>> index 6ea54a578cda..ec20b777b3cc 100644
>> --- a/include/drm/drm_device.h
>> +++ b/include/drm/drm_device.h
>> @@ -325,6 +325,10 @@ struct drm_device {
>>   	 * Root directory for debugfs files.
>>   	 */
>>   	struct dentry *debugfs_root;
>> +	/**
>> +	 * @drm_debugfs_root;
>> +	 */
>> +	struct dentry *drm_debugfs_root;
>>   };
>>   
>>   #endif
>> 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;
>>   };
>>   
>>   /**