drm: add debugfs support on per client-id basis

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 debugfs file which show the process
information for the client and create a symlink back
to the parent drm device from each client.

Signed-off-by: Sunil Khatri <[e-mail]>
Reviewed-by: Christian König <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Christian König <[e-mail]>

drivers/gpu/drm/drm_debugfs.c

···
 	debugfs_remove(drm_debugfs_root);
 }
 
+static int drm_debugfs_proc_info_show(struct seq_file *m, void *unused)
+{
+	struct pid *pid;
+	struct task_struct *task;
+	struct drm_file *file = m->private;
+
+	if (!file)
+		return -EINVAL;
+
+	rcu_read_lock();
+	pid = rcu_dereference(file->pid);
+	task = pid_task(pid, PIDTYPE_TGID);
+
+	seq_printf(m, "pid: %d\n", task ? task->pid : 0);
+	seq_printf(m, "comm: %s\n", task ? task->comm : "Unset");
+	rcu_read_unlock();
+	return 0;
+}
+
+static int drm_debufs_proc_info_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, drm_debugfs_proc_info_show, inode->i_private);
+}
+
+static const struct file_operations drm_debugfs_proc_info_fops = {
+	.owner = THIS_MODULE,
+	.open = drm_debufs_proc_info_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = single_release,
+};
+
+/**
+ * drm_debugfs_clients_add - Add a per client debugfs directory
+ * @file: drm_file for a client
+ *
+ * Create the debugfs directory for each client. This will be used to populate
+ * driver specific data for each client.
+ *
+ * Also add the process information debugfs file for each client to tag
+ * which client belongs to which process.
+ */
+void drm_debugfs_clients_add(struct drm_file *file)
+{
+	char *client;
+
+	client = kasprintf(GFP_KERNEL, "client-%llu", file->client_id);
+	if (!client)
+		return;
+
+	/* Create a debugfs directory for the client in root on drm debugfs */
+	file->debugfs_client = debugfs_create_dir(client, drm_debugfs_root);
+	kfree(client);
+
+	debugfs_create_file("proc_info", 0444, file->debugfs_client, file,
+			    &drm_debugfs_proc_info_fops);
+
+	client = kasprintf(GFP_KERNEL, "../%s", file->minor->dev->unique);
+	if (!client)
+		return;
+
+	/* Create a link from client_id to the drm device this client id belongs to */
+	debugfs_create_symlink("device", file->debugfs_client, client);
+	kfree(client);
+}
+
+/**
+ * drm_debugfs_clients_remove - removes all debugfs directories and files
+ * @file: drm_file for a client
+ *
+ * Removes the debugfs directories recursively from the client directory.
+ *
+ * There is also a possibility that debugfs files are open while the drm_file
+ * is released.
+ */
+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

drivers/gpu/drm/drm_file.c

···
 #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"
···
 
 	drm_prime_init_file_private(&file->prime);
 
+	if (!drm_core_check_feature(dev, DRIVER_COMPUTE_ACCEL))
+		drm_debugfs_clients_add(file);
+
 	if (dev->driver->open) {
 		ret = dev->driver->open(dev, file);
 		if (ret < 0)
···
 		drm_syncobj_release(file);
 	if (drm_core_check_feature(dev, DRIVER_GEM))
 		drm_gem_release(dev, file);
+
+	if (!drm_core_check_feature(dev, DRIVER_COMPUTE_ACCEL))
+		drm_debugfs_clients_remove(file);
+
 	put_pid(rcu_access_pointer(file->pid));
 	kfree(file);
 
···
 		     current->comm, task_pid_nr(current),
 		     (long)old_encode_dev(file->minor->kdev->devt),
 		     atomic_read(&dev->open_count));
+
+	if (!drm_core_check_feature(dev, DRIVER_COMPUTE_ACCEL))
+		drm_debugfs_clients_remove(file);
 
 	drm_events_release(file);
 

include/drm/drm_debugfs.h

···
 
 int drm_debugfs_gpuva_info(struct seq_file *m,
 			   struct drm_gpuvm *gpuvm);
+
+void 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,
···
 					 struct drm_gpuvm *gpuvm)
 {
 	return 0;
+}
+
+static inline void drm_debugfs_clients_add(struct drm_file *file)
+{
+}
+
+static inline void drm_debugfs_clients_remove(struct drm_file *file)
+{
 }
 #endif
 

include/drm/drm_file.h

···
 	 * @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;
 };
 
 /**