[PATCH v2 2/2] drm: add debugfs support on per client-id basis
Khatri, Sunil
sukhatri at amd.com
Mon Jun 16 14:32:43 UTC 2025
On 6/16/2025 6:26 PM, Christian König wrote:
> On 6/16/25 14:25, Khatri, Sunil wrote:
>> 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.
> drm_debugfs_root is currently a global variable in drm_drv.c, but if we move it to drm_debugfs.c all functions in that file could use it.
The global variable drm_debugfs_root is global variable in drm_drv.c and
a lot of function there are dependent on it. So no matter where we move
the variable we need to have a reference of dentry in drm_drv.c too and
drm_device is the only thing that is being used in drm_drv.c.
eg:
drm_core_init is using it and there is no structure there to use to have
a reference to this node.
drm_minor_register also uses the same root to create the device nodes
and we cant move all the code from drm_drv.c so we are stuck again how
to get the reference in drm_debugfs.c
I am trying to explore if its possible but if there is anything you
could suggest appreciate that. What is in the current patch is we have a
reference of root in drm_device itself like drm core is parent to every
drm device, could use a different name like parent_debugfs or something
like that.
Regards
Sunil Khatri
>
> Including the new functions for creating the per-client debugfs directory.
>
> Regards,
> Christian.
>
>
>> ~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;
>>>> };
>>>> /**
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